diff --git a/docs/api.rst b/docs/api.rst
index f1ba4d9c..fd7c98e4 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -60,6 +60,24 @@ connection class::
     Elasticsearch server. This timeout is internal and doesn't guarantee that the
     request will end in the specified time.
 
+Tracking Requests with Opaque ID
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You can enrich your requests against Elasticsearch with an identifier string, that allows you to discover this identifier
+in `deprecation logs <https://www.elastic.co/guide/en/elasticsearch/reference/7.4/logging.html#deprecation-logging>`_, to support you with
+`identifying search slow log origin <https://www.elastic.co/guide/en/elasticsearch/reference/7.4/index-modules-slowlog.html#_identifying_search_slow_log_origin>`_
+or to help with `identifying running tasks <https://www.elastic.co/guide/en/elasticsearch/reference/current/tasks.html#_identifying_running_tasks>`_.
+
+ .. code-block:: python
+
+    import elasticsearch
+
+    # You can add to the client to apply to all requests
+    client = elasticsearch.Elasticsearch(opaque_id="app17@dc06.eu_user1234")
+
+    # Or you can apply per-request for more granularity.
+    resp = client.get(index="test", id="1", opaque_id="app17@dc06.eu_user1234")
+
 
 .. py:module:: elasticsearch
 
diff --git a/elasticsearch/client/__init__.py b/elasticsearch/client/__init__.py
index 2673e6c1..43239f6e 100644
--- a/elasticsearch/client/__init__.py
+++ b/elasticsearch/client/__init__.py
@@ -270,25 +270,29 @@ class Elasticsearch(object):
 
     # AUTO-GENERATED-API-DEFINITIONS #
     @query_params()
-    def ping(self, params=None):
+    def ping(self, params=None, headers=None):
         """
         Returns whether the cluster is running.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/index.html>`_
 
         """
         try:
-            return self.transport.perform_request("HEAD", "/", params=params)
+            return self.transport.perform_request(
+                "HEAD", "/", params=params, headers=headers
+            )
         except TransportError:
             return False
 
     @query_params()
-    def info(self, params=None):
+    def info(self, params=None, headers=None):
         """
         Returns basic information about the cluster.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/index.html>`_
 
         """
-        return self.transport.perform_request("GET", "/", params=params)
+        return self.transport.perform_request(
+            "GET", "/", params=params, headers=headers
+        )
 
     @query_params(
         "pipeline",
@@ -299,7 +303,7 @@ class Elasticsearch(object):
         "version_type",
         "wait_for_active_shards",
     )
-    def create(self, index, id, body, doc_type=None, params=None):
+    def create(self, index, id, body, doc_type=None, params=None, headers=None):
         """
         Creates a new document in the index.  Returns a 409 response when a document
         with a same ID already exists in the index.
@@ -334,7 +338,11 @@ class Elasticsearch(object):
             doc_type = "_doc"
 
         return self.transport.perform_request(
-            "PUT", _make_path(index, doc_type, id, "_create"), params=params, body=body
+            "PUT",
+            _make_path(index, doc_type, id, "_create"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -349,7 +357,7 @@ class Elasticsearch(object):
         "version_type",
         "wait_for_active_shards",
     )
-    def index(self, index, body, doc_type=None, id=None, params=None):
+    def index(self, index, body, doc_type=None, id=None, params=None, headers=None):
         """
         Creates or updates a document in an index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-index_.html>`_
@@ -395,6 +403,7 @@ class Elasticsearch(object):
             "POST" if id in SKIP_IN_PATH else "PUT",
             _make_path(index, doc_type, id),
             params=params,
+            headers=headers,
             body=body,
         )
 
@@ -408,7 +417,7 @@ class Elasticsearch(object):
         "timeout",
         "wait_for_active_shards",
     )
-    def bulk(self, body, index=None, doc_type=None, params=None):
+    def bulk(self, body, index=None, doc_type=None, params=None, headers=None):
         """
         Allows to perform multiple index/update/delete operations in a single request.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-bulk.html>`_
@@ -446,11 +455,15 @@ class Elasticsearch(object):
 
         body = _bulk_body(self.transport.serializer, body)
         return self.transport.perform_request(
-            "POST", _make_path(index, doc_type, "_bulk"), params=params, body=body
+            "POST",
+            _make_path(index, doc_type, "_bulk"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def clear_scroll(self, body=None, scroll_id=None, params=None):
+    def clear_scroll(self, body=None, scroll_id=None, params=None, headers=None):
         """
         Explicitly clears the search context for a scroll.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/search-request-body.html#_clear_scroll_api>`_
@@ -467,7 +480,7 @@ class Elasticsearch(object):
             params["scroll_id"] = scroll_id
 
         return self.transport.perform_request(
-            "DELETE", "/_search/scroll", params=params, body=body
+            "DELETE", "/_search/scroll", params=params, headers=headers, body=body
         )
 
     @query_params(
@@ -486,7 +499,7 @@ class Elasticsearch(object):
         "routing",
         "terminate_after",
     )
-    def count(self, body=None, index=None, doc_type=None, params=None):
+    def count(self, body=None, index=None, doc_type=None, params=None, headers=None):
         """
         Returns number of documents matching a query.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/search-count.html>`_
@@ -526,7 +539,11 @@ class Elasticsearch(object):
             reaching which the query execution will terminate early
         """
         return self.transport.perform_request(
-            "POST", _make_path(index, doc_type, "_count"), params=params, body=body
+            "POST",
+            _make_path(index, doc_type, "_count"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -539,7 +556,7 @@ class Elasticsearch(object):
         "version_type",
         "wait_for_active_shards",
     )
-    def delete(self, index, id, doc_type=None, params=None):
+    def delete(self, index, id, doc_type=None, params=None, headers=None):
         """
         Removes a document from the index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-delete.html>`_
@@ -576,7 +593,7 @@ class Elasticsearch(object):
             doc_type = "_doc"
 
         return self.transport.perform_request(
-            "DELETE", _make_path(index, doc_type, id), params=params
+            "DELETE", _make_path(index, doc_type, id), params=params, headers=headers
         )
 
     @query_params(
@@ -613,7 +630,7 @@ class Elasticsearch(object):
         "wait_for_active_shards",
         "wait_for_completion",
     )
-    def delete_by_query(self, index, body, doc_type=None, params=None):
+    def delete_by_query(self, index, body, doc_type=None, params=None, headers=None):
         """
         Deletes documents matching the provided query.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-delete-by-query.html>`_
@@ -702,11 +719,12 @@ class Elasticsearch(object):
             "POST",
             _make_path(index, doc_type, "_delete_by_query"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("requests_per_second")
-    def delete_by_query_rethrottle(self, task_id, params=None):
+    def delete_by_query_rethrottle(self, task_id, params=None, headers=None):
         """
         Changes the number of requests per second for a particular Delete By Query
         operation.
@@ -723,10 +741,11 @@ class Elasticsearch(object):
             "POST",
             _make_path("_delete_by_query", task_id, "_rethrottle"),
             params=params,
+            headers=headers,
         )
 
     @query_params("master_timeout", "timeout")
-    def delete_script(self, id, params=None):
+    def delete_script(self, id, params=None, headers=None):
         """
         Deletes a script.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-scripting.html>`_
@@ -739,7 +758,7 @@ class Elasticsearch(object):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_scripts", id), params=params
+            "DELETE", _make_path("_scripts", id), params=params, headers=headers
         )
 
     @query_params(
@@ -754,7 +773,7 @@ class Elasticsearch(object):
         "version",
         "version_type",
     )
-    def exists(self, index, id, doc_type=None, params=None):
+    def exists(self, index, id, doc_type=None, params=None, headers=None):
         """
         Returns information about whether a document exists in an index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-get.html>`_
@@ -790,7 +809,7 @@ class Elasticsearch(object):
             doc_type = "_doc"
 
         return self.transport.perform_request(
-            "HEAD", _make_path(index, doc_type, id), params=params
+            "HEAD", _make_path(index, doc_type, id), params=params, headers=headers
         )
 
     @query_params(
@@ -804,7 +823,7 @@ class Elasticsearch(object):
         "version",
         "version_type",
     )
-    def exists_source(self, index, id, doc_type=None, params=None):
+    def exists_source(self, index, id, doc_type=None, params=None, headers=None):
         """
         Returns information about whether a document source exists in an index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-get.html>`_
@@ -835,7 +854,10 @@ class Elasticsearch(object):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "HEAD", _make_path(index, doc_type, id, "_source"), params=params
+            "HEAD",
+            _make_path(index, doc_type, id, "_source"),
+            params=params,
+            headers=headers,
         )
 
     @query_params(
@@ -852,7 +874,7 @@ class Elasticsearch(object):
         "routing",
         "stored_fields",
     )
-    def explain(self, index, id, body=None, doc_type=None, params=None):
+    def explain(self, index, id, body=None, doc_type=None, params=None, headers=None):
         """
         Returns information about why a specific matches (or doesn't match) a query.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/search-explain.html>`_
@@ -891,7 +913,11 @@ class Elasticsearch(object):
             doc_type = "_doc"
 
         return self.transport.perform_request(
-            "GET", _make_path(index, doc_type, id, "_explain"), params=params, body=body
+            "GET",
+            _make_path(index, doc_type, id, "_explain"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -901,7 +927,7 @@ class Elasticsearch(object):
         "ignore_unavailable",
         "include_unmapped",
     )
-    def field_caps(self, index=None, params=None):
+    def field_caps(self, index=None, params=None, headers=None):
         """
         Returns the information about the capabilities of fields among multiple
         indices.
@@ -922,7 +948,7 @@ class Elasticsearch(object):
             be included in the response.
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_field_caps"), params=params
+            "GET", _make_path(index, "_field_caps"), params=params, headers=headers
         )
 
     @query_params(
@@ -937,7 +963,7 @@ class Elasticsearch(object):
         "version",
         "version_type",
     )
-    def get(self, index, id, doc_type=None, params=None):
+    def get(self, index, id, doc_type=None, params=None, headers=None):
         """
         Returns a document.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-get.html>`_
@@ -973,11 +999,11 @@ class Elasticsearch(object):
             doc_type = "_doc"
 
         return self.transport.perform_request(
-            "GET", _make_path(index, doc_type, id), params=params
+            "GET", _make_path(index, doc_type, id), params=params, headers=headers
         )
 
     @query_params("master_timeout")
-    def get_script(self, id, params=None):
+    def get_script(self, id, params=None, headers=None):
         """
         Returns a script.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-scripting.html>`_
@@ -989,7 +1015,7 @@ class Elasticsearch(object):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "GET", _make_path("_scripts", id), params=params
+            "GET", _make_path("_scripts", id), params=params, headers=headers
         )
 
     @query_params(
@@ -1003,7 +1029,7 @@ class Elasticsearch(object):
         "version",
         "version_type",
     )
-    def get_source(self, index, id, doc_type=None, params=None):
+    def get_source(self, index, id, doc_type=None, params=None, headers=None):
         """
         Returns the source of a document.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-get.html>`_
@@ -1037,7 +1063,10 @@ class Elasticsearch(object):
             doc_type = "_doc"
 
         return self.transport.perform_request(
-            "GET", _make_path(index, doc_type, id, "_source"), params=params
+            "GET",
+            _make_path(index, doc_type, id, "_source"),
+            params=params,
+            headers=headers,
         )
 
     @query_params(
@@ -1050,7 +1079,7 @@ class Elasticsearch(object):
         "routing",
         "stored_fields",
     )
-    def mget(self, body, index=None, doc_type=None, params=None):
+    def mget(self, body, index=None, doc_type=None, params=None, headers=None):
         """
         Allows to get multiple documents in one request.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-multi-get.html>`_
@@ -1080,7 +1109,11 @@ class Elasticsearch(object):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "GET", _make_path(index, doc_type, "_mget"), params=params, body=body
+            "GET",
+            _make_path(index, doc_type, "_mget"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -1092,7 +1125,7 @@ class Elasticsearch(object):
         "search_type",
         "typed_keys",
     )
-    def msearch(self, body, index=None, doc_type=None, params=None):
+    def msearch(self, body, index=None, doc_type=None, params=None, headers=None):
         """
         Allows to execute several search operations in one request.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/search-multi-search.html>`_
@@ -1132,13 +1165,19 @@ class Elasticsearch(object):
 
         body = _bulk_body(self.transport.serializer, body)
         return self.transport.perform_request(
-            "GET", _make_path(index, doc_type, "_msearch"), params=params, body=body
+            "GET",
+            _make_path(index, doc_type, "_msearch"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
         "max_concurrent_searches", "rest_total_hits_as_int", "search_type", "typed_keys"
     )
-    def msearch_template(self, body, index=None, doc_type=None, params=None):
+    def msearch_template(
+        self, body, index=None, doc_type=None, params=None, headers=None
+    ):
         """
         Allows to execute several search template operations in one request.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/search-multi-search.html>`_
@@ -1167,6 +1206,7 @@ class Elasticsearch(object):
             "GET",
             _make_path(index, doc_type, "_msearch", "template"),
             params=params,
+            headers=headers,
             body=body,
         )
 
@@ -1184,7 +1224,9 @@ class Elasticsearch(object):
         "version",
         "version_type",
     )
-    def mtermvectors(self, body=None, index=None, doc_type=None, params=None):
+    def mtermvectors(
+        self, body=None, index=None, doc_type=None, params=None, headers=None
+    ):
         """
         Returns multiple termvectors in one request.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-multi-termvectors.html>`_
@@ -1230,11 +1272,12 @@ class Elasticsearch(object):
             "GET",
             _make_path(index, doc_type, "_mtermvectors"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("master_timeout", "timeout")
-    def put_script(self, id, body, context=None, params=None):
+    def put_script(self, id, body, context=None, params=None, headers=None):
         """
         Creates or updates a script.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-scripting.html>`_
@@ -1251,11 +1294,15 @@ class Elasticsearch(object):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_scripts", id, context), params=params, body=body
+            "PUT",
+            _make_path("_scripts", id, context),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("allow_no_indices", "expand_wildcards", "ignore_unavailable")
-    def rank_eval(self, body, index=None, params=None):
+    def rank_eval(self, body, index=None, params=None, headers=None):
         """
         Allows to evaluate the quality of ranked search results over a set of typical
         search queries
@@ -1278,7 +1325,11 @@ class Elasticsearch(object):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "GET", _make_path(index, "_rank_eval"), params=params, body=body
+            "GET",
+            _make_path(index, "_rank_eval"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -1291,7 +1342,7 @@ class Elasticsearch(object):
         "wait_for_active_shards",
         "wait_for_completion",
     )
-    def reindex(self, body, params=None):
+    def reindex(self, body, params=None, headers=None):
         """
         Allows to copy documents from one index to another, optionally filtering the
         source documents by a query, changing the destination index settings, or
@@ -1324,11 +1375,11 @@ class Elasticsearch(object):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "POST", "/_reindex", params=params, body=body
+            "POST", "/_reindex", params=params, headers=headers, body=body
         )
 
     @query_params("requests_per_second")
-    def reindex_rethrottle(self, task_id, params=None):
+    def reindex_rethrottle(self, task_id, params=None, headers=None):
         """
         Changes the number of requests per second for a particular Reindex operation.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-reindex.html>`_
@@ -1341,11 +1392,14 @@ class Elasticsearch(object):
             raise ValueError("Empty value passed for a required argument 'task_id'.")
 
         return self.transport.perform_request(
-            "POST", _make_path("_reindex", task_id, "_rethrottle"), params=params
+            "POST",
+            _make_path("_reindex", task_id, "_rethrottle"),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def render_search_template(self, body=None, id=None, params=None):
+    def render_search_template(self, body=None, id=None, params=None, headers=None):
         """
         Allows to use the Mustache language to pre-render a search definition.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/search-template.html#_validating_templates>`_
@@ -1354,11 +1408,15 @@ class Elasticsearch(object):
         :arg id: The id of the stored search template
         """
         return self.transport.perform_request(
-            "GET", _make_path("_render", "template", id), params=params, body=body
+            "GET",
+            _make_path("_render", "template", id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def scripts_painless_execute(self, body=None, params=None):
+    def scripts_painless_execute(self, body=None, params=None, headers=None):
         """
         Allows an arbitrary script to be executed and a result to be returned
         `<https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html>`_
@@ -1366,11 +1424,15 @@ class Elasticsearch(object):
         :arg body: The script to execute
         """
         return self.transport.perform_request(
-            "GET", "/_scripts/painless/_execute", params=params, body=body
+            "GET",
+            "/_scripts/painless/_execute",
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("rest_total_hits_as_int", "scroll")
-    def scroll(self, body=None, scroll_id=None, params=None):
+    def scroll(self, body=None, scroll_id=None, params=None, headers=None):
         """
         Allows to retrieve a large numbers of results from a single search request.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/search-request-body.html#request-body-search-scroll>`_
@@ -1392,7 +1454,7 @@ class Elasticsearch(object):
             params["scroll_id"] = scroll_id
 
         return self.transport.perform_request(
-            "GET", "/_search/scroll", params=params, body=body
+            "GET", "/_search/scroll", params=params, headers=headers, body=body
         )
 
     @query_params(
@@ -1439,7 +1501,7 @@ class Elasticsearch(object):
         "typed_keys",
         "version",
     )
-    def search(self, body=None, index=None, doc_type=None, params=None):
+    def search(self, body=None, index=None, doc_type=None, params=None, headers=None):
         """
         Returns results matching a query.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/search-search.html>`_
@@ -1545,7 +1607,11 @@ class Elasticsearch(object):
             params["from"] = params.pop("from_")
 
         return self.transport.perform_request(
-            "GET", _make_path(index, doc_type, "_search"), params=params, body=body
+            "GET",
+            _make_path(index, doc_type, "_search"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -1556,7 +1622,7 @@ class Elasticsearch(object):
         "preference",
         "routing",
     )
-    def search_shards(self, index=None, params=None):
+    def search_shards(self, index=None, params=None, headers=None):
         """
         Returns information about the indices and shards that a search request would be
         executed against.
@@ -1579,7 +1645,7 @@ class Elasticsearch(object):
         :arg routing: Specific routing value
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_search_shards"), params=params
+            "GET", _make_path(index, "_search_shards"), params=params, headers=headers
         )
 
     @query_params(
@@ -1596,7 +1662,9 @@ class Elasticsearch(object):
         "search_type",
         "typed_keys",
     )
-    def search_template(self, body, index=None, doc_type=None, params=None):
+    def search_template(
+        self, body, index=None, doc_type=None, params=None, headers=None
+    ):
         """
         Allows to use the Mustache language to pre-render a search definition.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/search-template.html>`_
@@ -1639,6 +1707,7 @@ class Elasticsearch(object):
             "GET",
             _make_path(index, doc_type, "_search", "template"),
             params=params,
+            headers=headers,
             body=body,
         )
 
@@ -1655,7 +1724,9 @@ class Elasticsearch(object):
         "version",
         "version_type",
     )
-    def termvectors(self, index, body=None, doc_type=None, id=None, params=None):
+    def termvectors(
+        self, index, body=None, doc_type=None, id=None, params=None, headers=None
+    ):
         """
         Returns information and statistics about terms in the fields of a particular
         document.
@@ -1698,6 +1769,7 @@ class Elasticsearch(object):
             "GET",
             _make_path(index, doc_type, id, "_termvectors"),
             params=params,
+            headers=headers,
             body=body,
         )
 
@@ -1714,7 +1786,7 @@ class Elasticsearch(object):
         "timeout",
         "wait_for_active_shards",
     )
-    def update(self, index, id, body, doc_type=None, params=None):
+    def update(self, index, id, body, doc_type=None, params=None, headers=None):
         """
         Updates a document with a script or partial document.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-update.html>`_
@@ -1759,7 +1831,11 @@ class Elasticsearch(object):
             doc_type = "_doc"
 
         return self.transport.perform_request(
-            "POST", _make_path(index, doc_type, id, "_update"), params=params, body=body
+            "POST",
+            _make_path(index, doc_type, id, "_update"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -1799,7 +1875,9 @@ class Elasticsearch(object):
         "wait_for_active_shards",
         "wait_for_completion",
     )
-    def update_by_query(self, index, body=None, doc_type=None, params=None):
+    def update_by_query(
+        self, index, body=None, doc_type=None, params=None, headers=None
+    ):
         """
         Performs an update on every document in the index without changing the source,
         for example to pick up a mapping change.
@@ -1893,11 +1971,12 @@ class Elasticsearch(object):
             "POST",
             _make_path(index, doc_type, "_update_by_query"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("requests_per_second")
-    def update_by_query_rethrottle(self, task_id, params=None):
+    def update_by_query_rethrottle(self, task_id, params=None, headers=None):
         """
         Changes the number of requests per second for a particular Update By Query
         operation.
@@ -1914,4 +1993,5 @@ class Elasticsearch(object):
             "POST",
             _make_path("_update_by_query", task_id, "_rethrottle"),
             params=params,
+            headers=headers,
         )
diff --git a/elasticsearch/client/cat.py b/elasticsearch/client/cat.py
index 2ed9ff94..81a3fc2c 100644
--- a/elasticsearch/client/cat.py
+++ b/elasticsearch/client/cat.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path
 
 class CatClient(NamespacedClient):
     @query_params("format", "h", "help", "local", "s", "v")
-    def aliases(self, name=None, params=None):
+    def aliases(self, name=None, params=None, headers=None):
         """
         Shows information about currently configured aliases to indices including
         filter and routing infos.
@@ -21,11 +21,11 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "aliases", name), params=params
+            "GET", _make_path("_cat", "aliases", name), params=params, headers=headers
         )
 
     @query_params("bytes", "format", "h", "help", "local", "master_timeout", "s", "v")
-    def allocation(self, node_id=None, params=None):
+    def allocation(self, node_id=None, params=None, headers=None):
         """
         Provides a snapshot of how many shards are allocated to each data node and how
         much disk space they are using.
@@ -48,11 +48,14 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "allocation", node_id), params=params
+            "GET",
+            _make_path("_cat", "allocation", node_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params("format", "h", "help", "s", "v")
-    def count(self, index=None, params=None):
+    def count(self, index=None, params=None, headers=None):
         """
         Provides quick access to the document count of the entire cluster, or
         individual indices.
@@ -69,11 +72,11 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "count", index), params=params
+            "GET", _make_path("_cat", "count", index), params=params, headers=headers
         )
 
     @query_params("format", "h", "help", "s", "time", "ts", "v")
-    def health(self, params=None):
+    def health(self, params=None, headers=None):
         """
         Returns a concise representation of the cluster health.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-health.html>`_
@@ -90,10 +93,12 @@ class CatClient(NamespacedClient):
         :arg ts: Set to false to disable timestamping  Default: True
         :arg v: Verbose mode. Display column headers
         """
-        return self.transport.perform_request("GET", "/_cat/health", params=params)
+        return self.transport.perform_request(
+            "GET", "/_cat/health", params=params, headers=headers
+        )
 
     @query_params("help", "s")
-    def help(self, params=None):
+    def help(self, params=None, headers=None):
         """
         Returns help for the Cat APIs.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat.html>`_
@@ -102,7 +107,9 @@ class CatClient(NamespacedClient):
         :arg s: Comma-separated list of column names or column aliases
             to sort by
         """
-        return self.transport.perform_request("GET", "/_cat", params=params)
+        return self.transport.perform_request(
+            "GET", "/_cat", params=params, headers=headers
+        )
 
     @query_params(
         "bytes",
@@ -118,7 +125,7 @@ class CatClient(NamespacedClient):
         "time",
         "v",
     )
-    def indices(self, index=None, params=None):
+    def indices(self, index=None, params=None, headers=None):
         """
         Returns information about indices: number of primaries and replicas, document
         counts, disk size, ...
@@ -151,11 +158,11 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "indices", index), params=params
+            "GET", _make_path("_cat", "indices", index), params=params, headers=headers
         )
 
     @query_params("format", "h", "help", "local", "master_timeout", "s", "v")
-    def master(self, params=None):
+    def master(self, params=None, headers=None):
         """
         Returns information about the master node.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-master.html>`_
@@ -172,7 +179,9 @@ class CatClient(NamespacedClient):
             to sort by
         :arg v: Verbose mode. Display column headers
         """
-        return self.transport.perform_request("GET", "/_cat/master", params=params)
+        return self.transport.perform_request(
+            "GET", "/_cat/master", params=params, headers=headers
+        )
 
     @query_params(
         "bytes",
@@ -186,7 +195,7 @@ class CatClient(NamespacedClient):
         "time",
         "v",
     )
-    def nodes(self, params=None):
+    def nodes(self, params=None, headers=None):
         """
         Returns basic statistics about performance of cluster nodes.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-nodes.html>`_
@@ -210,12 +219,14 @@ class CatClient(NamespacedClient):
             (Milliseconds), micros (Microseconds), nanos (Nanoseconds)
         :arg v: Verbose mode. Display column headers
         """
-        return self.transport.perform_request("GET", "/_cat/nodes", params=params)
+        return self.transport.perform_request(
+            "GET", "/_cat/nodes", params=params, headers=headers
+        )
 
     @query_params(
         "active_only", "bytes", "detailed", "format", "h", "help", "s", "time", "v"
     )
-    def recovery(self, index=None, params=None):
+    def recovery(self, index=None, params=None, headers=None):
         """
         Returns information about index shard recoveries, both on-going completed.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-recovery.html>`_
@@ -242,13 +253,13 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "recovery", index), params=params
+            "GET", _make_path("_cat", "recovery", index), params=params, headers=headers
         )
 
     @query_params(
         "bytes", "format", "h", "help", "local", "master_timeout", "s", "time", "v"
     )
-    def shards(self, index=None, params=None):
+    def shards(self, index=None, params=None, headers=None):
         """
         Provides a detailed view of shard allocation on nodes.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-shards.html>`_
@@ -273,11 +284,11 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "shards", index), params=params
+            "GET", _make_path("_cat", "shards", index), params=params, headers=headers
         )
 
     @query_params("bytes", "format", "h", "help", "s", "v")
-    def segments(self, index=None, params=None):
+    def segments(self, index=None, params=None, headers=None):
         """
         Provides low-level information about the segments in the shards of an index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-segments.html>`_
@@ -295,11 +306,11 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "segments", index), params=params
+            "GET", _make_path("_cat", "segments", index), params=params, headers=headers
         )
 
     @query_params("format", "h", "help", "local", "master_timeout", "s", "time", "v")
-    def pending_tasks(self, params=None):
+    def pending_tasks(self, params=None, headers=None):
         """
         Returns a concise representation of the cluster pending tasks.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-pending-tasks.html>`_
@@ -320,11 +331,11 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", "/_cat/pending_tasks", params=params
+            "GET", "/_cat/pending_tasks", params=params, headers=headers
         )
 
     @query_params("format", "h", "help", "local", "master_timeout", "s", "size", "v")
-    def thread_pool(self, thread_pool_patterns=None, params=None):
+    def thread_pool(self, thread_pool_patterns=None, params=None, headers=None):
         """
         Returns cluster-wide thread pool statistics per node. By default the active,
         queue and rejected statistics are returned for all thread pools.
@@ -350,10 +361,11 @@ class CatClient(NamespacedClient):
             "GET",
             _make_path("_cat", "thread_pool", thread_pool_patterns),
             params=params,
+            headers=headers,
         )
 
     @query_params("bytes", "format", "h", "help", "s", "v")
-    def fielddata(self, fields=None, params=None):
+    def fielddata(self, fields=None, params=None, headers=None):
         """
         Shows how much heap memory is currently being used by fielddata on every data
         node in the cluster.
@@ -374,11 +386,14 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "fielddata", fields), params=params
+            "GET",
+            _make_path("_cat", "fielddata", fields),
+            params=params,
+            headers=headers,
         )
 
     @query_params("format", "h", "help", "local", "master_timeout", "s", "v")
-    def plugins(self, params=None):
+    def plugins(self, params=None, headers=None):
         """
         Returns information about installed plugins across nodes node.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-plugins.html>`_
@@ -395,10 +410,12 @@ class CatClient(NamespacedClient):
             to sort by
         :arg v: Verbose mode. Display column headers
         """
-        return self.transport.perform_request("GET", "/_cat/plugins", params=params)
+        return self.transport.perform_request(
+            "GET", "/_cat/plugins", params=params, headers=headers
+        )
 
     @query_params("format", "h", "help", "local", "master_timeout", "s", "v")
-    def nodeattrs(self, params=None):
+    def nodeattrs(self, params=None, headers=None):
         """
         Returns information about custom node attributes.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-nodeattrs.html>`_
@@ -415,10 +432,12 @@ class CatClient(NamespacedClient):
             to sort by
         :arg v: Verbose mode. Display column headers
         """
-        return self.transport.perform_request("GET", "/_cat/nodeattrs", params=params)
+        return self.transport.perform_request(
+            "GET", "/_cat/nodeattrs", params=params, headers=headers
+        )
 
     @query_params("format", "h", "help", "local", "master_timeout", "s", "v")
-    def repositories(self, params=None):
+    def repositories(self, params=None, headers=None):
         """
         Returns information about snapshot repositories registered in the cluster.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-repositories.html>`_
@@ -436,13 +455,13 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", "/_cat/repositories", params=params
+            "GET", "/_cat/repositories", params=params, headers=headers
         )
 
     @query_params(
         "format", "h", "help", "ignore_unavailable", "master_timeout", "s", "time", "v"
     )
-    def snapshots(self, repository=None, params=None):
+    def snapshots(self, repository=None, params=None, headers=None):
         """
         Returns all snapshots in a specific repository.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-snapshots.html>`_
@@ -465,7 +484,10 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "snapshots", repository), params=params
+            "GET",
+            _make_path("_cat", "snapshots", repository),
+            params=params,
+            headers=headers,
         )
 
     @query_params(
@@ -480,7 +502,7 @@ class CatClient(NamespacedClient):
         "time",
         "v",
     )
-    def tasks(self, params=None):
+    def tasks(self, params=None, headers=None):
         """
         Returns information about the tasks currently executing on one or more nodes in
         the cluster.
@@ -506,10 +528,12 @@ class CatClient(NamespacedClient):
             (Milliseconds), micros (Microseconds), nanos (Nanoseconds)
         :arg v: Verbose mode. Display column headers
         """
-        return self.transport.perform_request("GET", "/_cat/tasks", params=params)
+        return self.transport.perform_request(
+            "GET", "/_cat/tasks", params=params, headers=headers
+        )
 
     @query_params("format", "h", "help", "local", "master_timeout", "s", "v")
-    def templates(self, name=None, params=None):
+    def templates(self, name=None, params=None, headers=None):
         """
         Returns information about existing templates.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-templates.html>`_
@@ -528,5 +552,5 @@ class CatClient(NamespacedClient):
         :arg v: Verbose mode. Display column headers
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cat", "templates", name), params=params
+            "GET", _make_path("_cat", "templates", name), params=params, headers=headers
         )
diff --git a/elasticsearch/client/ccr.py b/elasticsearch/client/ccr.py
index 9796eb5a..1f7cc29b 100644
--- a/elasticsearch/client/ccr.py
+++ b/elasticsearch/client/ccr.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class CcrClient(NamespacedClient):
     @query_params()
-    def delete_auto_follow_pattern(self, name, params=None):
+    def delete_auto_follow_pattern(self, name, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-delete-auto-follow-pattern.html>`_
 
@@ -13,11 +13,14 @@ class CcrClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_ccr", "auto_follow", name), params=params
+            "DELETE",
+            _make_path("_ccr", "auto_follow", name),
+            params=params,
+            headers=headers,
         )
 
     @query_params("wait_for_active_shards")
-    def follow(self, index, body, params=None):
+    def follow(self, index, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-put-follow.html>`_
 
@@ -35,11 +38,15 @@ class CcrClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path(index, "_ccr", "follow"), params=params, body=body
+            "PUT",
+            _make_path(index, "_ccr", "follow"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def follow_info(self, index, params=None):
+    def follow_info(self, index, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-get-follow-info.html>`_
 
@@ -50,11 +57,11 @@ class CcrClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "GET", _make_path(index, "_ccr", "info"), params=params
+            "GET", _make_path(index, "_ccr", "info"), params=params, headers=headers
         )
 
     @query_params()
-    def follow_stats(self, index, params=None):
+    def follow_stats(self, index, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-get-follow-stats.html>`_
 
@@ -65,11 +72,11 @@ class CcrClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "GET", _make_path(index, "_ccr", "stats"), params=params
+            "GET", _make_path(index, "_ccr", "stats"), params=params, headers=headers
         )
 
     @query_params()
-    def forget_follower(self, index, body, params=None):
+    def forget_follower(self, index, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current>`_
 
@@ -88,22 +95,26 @@ class CcrClient(NamespacedClient):
             "POST",
             _make_path(index, "_ccr", "forget_follower"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def get_auto_follow_pattern(self, name=None, params=None):
+    def get_auto_follow_pattern(self, name=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-get-auto-follow-pattern.html>`_
 
         :arg name: The name of the auto follow pattern.
         """
         return self.transport.perform_request(
-            "GET", _make_path("_ccr", "auto_follow", name), params=params
+            "GET",
+            _make_path("_ccr", "auto_follow", name),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def pause_follow(self, index, params=None):
+    def pause_follow(self, index, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-post-pause-follow.html>`_
 
@@ -114,11 +125,14 @@ class CcrClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(index, "_ccr", "pause_follow"), params=params
+            "POST",
+            _make_path(index, "_ccr", "pause_follow"),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def put_auto_follow_pattern(self, name, body, params=None):
+    def put_auto_follow_pattern(self, name, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-put-auto-follow-pattern.html>`_
 
@@ -130,11 +144,15 @@ class CcrClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_ccr", "auto_follow", name), params=params, body=body
+            "PUT",
+            _make_path("_ccr", "auto_follow", name),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def resume_follow(self, index, body=None, params=None):
+    def resume_follow(self, index, body=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-post-resume-follow.html>`_
 
@@ -146,19 +164,25 @@ class CcrClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(index, "_ccr", "resume_follow"), params=params, body=body
+            "POST",
+            _make_path(index, "_ccr", "resume_follow"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def stats(self, params=None):
+    def stats(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-get-stats.html>`_
 
         """
-        return self.transport.perform_request("GET", "/_ccr/stats", params=params)
+        return self.transport.perform_request(
+            "GET", "/_ccr/stats", params=params, headers=headers
+        )
 
     @query_params()
-    def unfollow(self, index, params=None):
+    def unfollow(self, index, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current>`_
 
@@ -169,11 +193,14 @@ class CcrClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(index, "_ccr", "unfollow"), params=params
+            "POST",
+            _make_path(index, "_ccr", "unfollow"),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def pause_auto_follow_pattern(self, name, params=None):
+    def pause_auto_follow_pattern(self, name, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-pause-auto-follow-pattern.html>`_
 
@@ -184,11 +211,14 @@ class CcrClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "POST", _make_path("_ccr", "auto_follow", name, "pause"), params=params
+            "POST",
+            _make_path("_ccr", "auto_follow", name, "pause"),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def resume_auto_follow_pattern(self, name, params=None):
+    def resume_auto_follow_pattern(self, name, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-resume-auto-follow-pattern.html>`_
 
@@ -199,5 +229,8 @@ class CcrClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "POST", _make_path("_ccr", "auto_follow", name, "resume"), params=params
+            "POST",
+            _make_path("_ccr", "auto_follow", name, "resume"),
+            params=params,
+            headers=headers,
         )
diff --git a/elasticsearch/client/cluster.py b/elasticsearch/client/cluster.py
index 14fa7e94..285201a7 100644
--- a/elasticsearch/client/cluster.py
+++ b/elasticsearch/client/cluster.py
@@ -15,7 +15,7 @@ class ClusterClient(NamespacedClient):
         "wait_for_nodes",
         "wait_for_status",
     )
-    def health(self, index=None, params=None):
+    def health(self, index=None, params=None, headers=None):
         """
         Returns basic information about the health of the cluster.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-health.html>`_
@@ -46,11 +46,14 @@ class ClusterClient(NamespacedClient):
             Valid choices: green, yellow, red
         """
         return self.transport.perform_request(
-            "GET", _make_path("_cluster", "health", index), params=params
+            "GET",
+            _make_path("_cluster", "health", index),
+            params=params,
+            headers=headers,
         )
 
     @query_params("local", "master_timeout")
-    def pending_tasks(self, params=None):
+    def pending_tasks(self, params=None, headers=None):
         """
         Returns a list of any cluster-level changes (e.g. create index, update mapping,
         allocate or fail shard) which have not yet been executed.
@@ -61,7 +64,7 @@ class ClusterClient(NamespacedClient):
         :arg master_timeout: Specify timeout for connection to master
         """
         return self.transport.perform_request(
-            "GET", "/_cluster/pending_tasks", params=params
+            "GET", "/_cluster/pending_tasks", params=params, headers=headers
         )
 
     @query_params(
@@ -74,7 +77,7 @@ class ClusterClient(NamespacedClient):
         "wait_for_metadata_version",
         "wait_for_timeout",
     )
-    def state(self, metric=None, index=None, params=None):
+    def state(self, metric=None, index=None, params=None, headers=None):
         """
         Returns a comprehensive information about the state of the cluster.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-state.html>`_
@@ -106,11 +109,14 @@ class ClusterClient(NamespacedClient):
             metric = "_all"
 
         return self.transport.perform_request(
-            "GET", _make_path("_cluster", "state", metric, index), params=params
+            "GET",
+            _make_path("_cluster", "state", metric, index),
+            params=params,
+            headers=headers,
         )
 
     @query_params("flat_settings", "timeout")
-    def stats(self, node_id=None, params=None):
+    def stats(self, node_id=None, params=None, headers=None):
         """
         Returns high-level overview of cluster statistics.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-stats.html>`_
@@ -129,12 +135,13 @@ class ClusterClient(NamespacedClient):
             if node_id in SKIP_IN_PATH
             else _make_path("_cluster", "stats", "nodes", node_id),
             params=params,
+            headers=headers,
         )
 
     @query_params(
         "dry_run", "explain", "master_timeout", "metric", "retry_failed", "timeout"
     )
-    def reroute(self, body=None, params=None):
+    def reroute(self, body=None, params=None, headers=None):
         """
         Allows to manually change the allocation of individual shards in the cluster.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-reroute.html>`_
@@ -155,11 +162,11 @@ class ClusterClient(NamespacedClient):
         :arg timeout: Explicit operation timeout
         """
         return self.transport.perform_request(
-            "POST", "/_cluster/reroute", params=params, body=body
+            "POST", "/_cluster/reroute", params=params, headers=headers, body=body
         )
 
     @query_params("flat_settings", "include_defaults", "master_timeout", "timeout")
-    def get_settings(self, params=None):
+    def get_settings(self, params=None, headers=None):
         """
         Returns cluster settings.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-update-settings.html>`_
@@ -173,11 +180,11 @@ class ClusterClient(NamespacedClient):
         :arg timeout: Explicit operation timeout
         """
         return self.transport.perform_request(
-            "GET", "/_cluster/settings", params=params
+            "GET", "/_cluster/settings", params=params, headers=headers
         )
 
     @query_params("flat_settings", "master_timeout", "timeout")
-    def put_settings(self, body, params=None):
+    def put_settings(self, body, params=None, headers=None):
         """
         Updates the cluster settings.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-update-settings.html>`_
@@ -194,20 +201,22 @@ class ClusterClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "PUT", "/_cluster/settings", params=params, body=body
+            "PUT", "/_cluster/settings", params=params, headers=headers, body=body
         )
 
     @query_params()
-    def remote_info(self, params=None):
+    def remote_info(self, params=None, headers=None):
         """
         Returns the information about configured remote clusters.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-remote-info.html>`_
 
         """
-        return self.transport.perform_request("GET", "/_remote/info", params=params)
+        return self.transport.perform_request(
+            "GET", "/_remote/info", params=params, headers=headers
+        )
 
     @query_params("include_disk_info", "include_yes_decisions")
-    def allocation_explain(self, body=None, params=None):
+    def allocation_explain(self, body=None, params=None, headers=None):
         """
         Provides explanations for shard allocations in the cluster.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-allocation-explain.html>`_
@@ -220,5 +229,9 @@ class ClusterClient(NamespacedClient):
             explanation (default: false)
         """
         return self.transport.perform_request(
-            "GET", "/_cluster/allocation/explain", params=params, body=body
+            "GET",
+            "/_cluster/allocation/explain",
+            params=params,
+            headers=headers,
+            body=body,
         )
diff --git a/elasticsearch/client/data_frame.py b/elasticsearch/client/data_frame.py
index fc758ce0..e7ff49a5 100644
--- a/elasticsearch/client/data_frame.py
+++ b/elasticsearch/client/data_frame.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class Data_FrameClient(NamespacedClient):
     @query_params()
-    def delete_data_frame_transform(self, transform_id, params=None):
+    def delete_data_frame_transform(self, transform_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/delete-data-frame-transform.html>`_
 
@@ -17,10 +17,11 @@ class Data_FrameClient(NamespacedClient):
             "DELETE",
             _make_path("_data_frame", "transforms", transform_id),
             params=params,
+            headers=headers,
         )
 
     @query_params("from_", "size")
-    def get_data_frame_transform(self, transform_id=None, params=None):
+    def get_data_frame_transform(self, transform_id=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/get-data-frame-transform.html>`_
 
@@ -30,11 +31,16 @@ class Data_FrameClient(NamespacedClient):
         :arg size: specifies a max number of transforms to get, defaults to 100
         """
         return self.transport.perform_request(
-            "GET", _make_path("_data_frame", "transforms", transform_id), params=params
+            "GET",
+            _make_path("_data_frame", "transforms", transform_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def get_data_frame_transform_stats(self, transform_id=None, params=None):
+    def get_data_frame_transform_stats(
+        self, transform_id=None, params=None, headers=None
+    ):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/get-data-frame-transform-stats.html>`_
 
@@ -48,7 +54,7 @@ class Data_FrameClient(NamespacedClient):
         )
 
     @query_params()
-    def preview_data_frame_transform(self, body, params=None):
+    def preview_data_frame_transform(self, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/preview-data-frame-transform.html>`_
 
@@ -57,11 +63,15 @@ class Data_FrameClient(NamespacedClient):
         if body in SKIP_IN_PATH:
             raise ValueError("Empty value passed for a required argument 'body'.")
         return self.transport.perform_request(
-            "POST", "/_data_frame/transforms/_preview", params=params, body=body
+            "POST",
+            "/_data_frame/transforms/_preview",
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def put_data_frame_transform(self, transform_id, body, params=None):
+    def put_data_frame_transform(self, transform_id, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/put-data-frame-transform.html>`_
 
@@ -75,11 +85,12 @@ class Data_FrameClient(NamespacedClient):
             "PUT",
             _make_path("_data_frame", "transforms", transform_id),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("timeout")
-    def start_data_frame_transform(self, transform_id, params=None):
+    def start_data_frame_transform(self, transform_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/start-data-frame-transform.html>`_
 
@@ -94,10 +105,11 @@ class Data_FrameClient(NamespacedClient):
             "POST",
             _make_path("_data_frame", "transforms", transform_id, "_start"),
             params=params,
+            headers=headers,
         )
 
     @query_params("timeout", "wait_for_completion")
-    def stop_data_frame_transform(self, transform_id, params=None):
+    def stop_data_frame_transform(self, transform_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/stop-data-frame-transform.html>`_
 
@@ -115,4 +127,5 @@ class Data_FrameClient(NamespacedClient):
             "POST",
             _make_path("_data_frame", "transforms", transform_id, "_stop"),
             params=params,
+            headers=headers,
         )
diff --git a/elasticsearch/client/deprecation.py b/elasticsearch/client/deprecation.py
index 48e99446..8b0e9d70 100644
--- a/elasticsearch/client/deprecation.py
+++ b/elasticsearch/client/deprecation.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path
 
 class DeprecationClient(NamespacedClient):
     @query_params()
-    def info(self, index=None, params=None):
+    def info(self, index=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/migration/current/migration-api-deprecation.html>`_
 
@@ -13,4 +13,5 @@ class DeprecationClient(NamespacedClient):
             "GET",
             _make_path(index, "_xpack", "migration", "deprecations"),
             params=params,
+            headers=headers,
         )
diff --git a/elasticsearch/client/enrich.py b/elasticsearch/client/enrich.py
index d2952437..2f38adb3 100644
--- a/elasticsearch/client/enrich.py
+++ b/elasticsearch/client/enrich.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class EnrichClient(NamespacedClient):
     @query_params()
-    def delete_policy(self, name, params=None):
+    def delete_policy(self, name, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/enrich-delete-policy.html>`_
 
@@ -13,11 +13,14 @@ class EnrichClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_enrich", "policy", name), params=params
+            "DELETE",
+            _make_path("_enrich", "policy", name),
+            params=params,
+            headers=headers,
         )
 
     @query_params("wait_for_completion")
-    def execute_policy(self, name, params=None):
+    def execute_policy(self, name, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/enrich-execute-policy.html>`_
 
@@ -29,22 +32,25 @@ class EnrichClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_enrich", "policy", name, "_execute"), params=params
+            "PUT",
+            _make_path("_enrich", "policy", name, "_execute"),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def get_policy(self, name=None, params=None):
+    def get_policy(self, name=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/enrich-get-policy.html>`_
 
         :arg name: The name of the enrich policy
         """
         return self.transport.perform_request(
-            "GET", _make_path("_enrich", "policy", name), params=params
+            "GET", _make_path("_enrich", "policy", name), params=params, headers=headers
         )
 
     @query_params()
-    def put_policy(self, name, body, params=None):
+    def put_policy(self, name, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/enrich-put-policy.html>`_
 
@@ -56,13 +62,19 @@ class EnrichClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_enrich", "policy", name), params=params, body=body
+            "PUT",
+            _make_path("_enrich", "policy", name),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def stats(self, params=None):
+    def stats(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/enrich-stats.html>`_
 
         """
-        return self.transport.perform_request("GET", "/_enrich/_stats", params=params)
+        return self.transport.perform_request(
+            "GET", "/_enrich/_stats", params=params, headers=headers
+        )
diff --git a/elasticsearch/client/graph.py b/elasticsearch/client/graph.py
index cf8f57b0..4f5bce45 100644
--- a/elasticsearch/client/graph.py
+++ b/elasticsearch/client/graph.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class GraphClient(NamespacedClient):
     @query_params("routing", "timeout")
-    def explore(self, index, body=None, doc_type=None, params=None):
+    def explore(self, index, body=None, doc_type=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/graph-explore-api.html>`_
 
@@ -22,5 +22,6 @@ class GraphClient(NamespacedClient):
             "GET",
             _make_path(index, doc_type, "_graph", "explore"),
             params=params,
+            headers=headers,
             body=body,
         )
diff --git a/elasticsearch/client/ilm.py b/elasticsearch/client/ilm.py
index 142a343c..a7a14700 100644
--- a/elasticsearch/client/ilm.py
+++ b/elasticsearch/client/ilm.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class IlmClient(NamespacedClient):
     @query_params()
-    def delete_lifecycle(self, policy, params=None):
+    def delete_lifecycle(self, policy, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-delete-lifecycle.html>`_
 
@@ -13,11 +13,14 @@ class IlmClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'policy'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_ilm", "policy", policy), params=params
+            "DELETE",
+            _make_path("_ilm", "policy", policy),
+            params=params,
+            headers=headers,
         )
 
     @query_params("only_errors", "only_managed")
-    def explain_lifecycle(self, index, params=None):
+    def explain_lifecycle(self, index, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-explain-lifecycle.html>`_
 
@@ -31,30 +34,32 @@ class IlmClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "GET", _make_path(index, "_ilm", "explain"), params=params
+            "GET", _make_path(index, "_ilm", "explain"), params=params, headers=headers
         )
 
     @query_params()
-    def get_lifecycle(self, policy=None, params=None):
+    def get_lifecycle(self, policy=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-get-lifecycle.html>`_
 
         :arg policy: The name of the index lifecycle policy
         """
         return self.transport.perform_request(
-            "GET", _make_path("_ilm", "policy", policy), params=params
+            "GET", _make_path("_ilm", "policy", policy), params=params, headers=headers
         )
 
     @query_params()
-    def get_status(self, params=None):
+    def get_status(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-get-status.html>`_
 
         """
-        return self.transport.perform_request("GET", "/_ilm/status", params=params)
+        return self.transport.perform_request(
+            "GET", "/_ilm/status", params=params, headers=headers
+        )
 
     @query_params()
-    def move_to_step(self, index, body=None, params=None):
+    def move_to_step(self, index, body=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-move-to-step.html>`_
 
@@ -66,11 +71,15 @@ class IlmClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path("_ilm", "move", index), params=params, body=body
+            "POST",
+            _make_path("_ilm", "move", index),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def put_lifecycle(self, policy, body=None, params=None):
+    def put_lifecycle(self, policy, body=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-put-lifecycle.html>`_
 
@@ -81,11 +90,15 @@ class IlmClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'policy'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_ilm", "policy", policy), params=params, body=body
+            "PUT",
+            _make_path("_ilm", "policy", policy),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def remove_policy(self, index, params=None):
+    def remove_policy(self, index, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-remove-policy.html>`_
 
@@ -95,11 +108,11 @@ class IlmClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(index, "_ilm", "remove"), params=params
+            "POST", _make_path(index, "_ilm", "remove"), params=params, headers=headers
         )
 
     @query_params()
-    def retry(self, index, params=None):
+    def retry(self, index, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-retry-policy.html>`_
 
@@ -110,21 +123,25 @@ class IlmClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(index, "_ilm", "retry"), params=params
+            "POST", _make_path(index, "_ilm", "retry"), params=params, headers=headers
         )
 
     @query_params()
-    def start(self, params=None):
+    def start(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-start.html>`_
 
         """
-        return self.transport.perform_request("POST", "/_ilm/start", params=params)
+        return self.transport.perform_request(
+            "POST", "/_ilm/start", params=params, headers=headers
+        )
 
     @query_params()
-    def stop(self, params=None):
+    def stop(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/ilm-stop.html>`_
 
         """
-        return self.transport.perform_request("POST", "/_ilm/stop", params=params)
+        return self.transport.perform_request(
+            "POST", "/_ilm/stop", params=params, headers=headers
+        )
diff --git a/elasticsearch/client/indices.py b/elasticsearch/client/indices.py
index fde12ba4..b6518bff 100644
--- a/elasticsearch/client/indices.py
+++ b/elasticsearch/client/indices.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class IndicesClient(NamespacedClient):
     @query_params()
-    def analyze(self, body=None, index=None, params=None):
+    def analyze(self, body=None, index=None, params=None, headers=None):
         """
         Performs the analysis process on a text and return the tokens breakdown of the
         text.
@@ -15,11 +15,15 @@ class IndicesClient(NamespacedClient):
         :arg index: The name of the index to scope the operation
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_analyze"), params=params, body=body
+            "GET",
+            _make_path(index, "_analyze"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("allow_no_indices", "expand_wildcards", "ignore_unavailable")
-    def refresh(self, index=None, params=None):
+    def refresh(self, index=None, params=None, headers=None):
         """
         Performs the refresh operation in one or more indices.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-refresh.html>`_
@@ -36,7 +40,7 @@ class IndicesClient(NamespacedClient):
             should be ignored when unavailable (missing or closed)
         """
         return self.transport.perform_request(
-            "POST", _make_path(index, "_refresh"), params=params
+            "POST", _make_path(index, "_refresh"), params=params, headers=headers
         )
 
     @query_params(
@@ -46,7 +50,7 @@ class IndicesClient(NamespacedClient):
         "ignore_unavailable",
         "wait_if_ongoing",
     )
-    def flush(self, index=None, params=None):
+    def flush(self, index=None, params=None, headers=None):
         """
         Performs the flush operation on one or more indices.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-flush.html>`_
@@ -72,13 +76,13 @@ class IndicesClient(NamespacedClient):
             be skipped iff if another flush operation is already running.
         """
         return self.transport.perform_request(
-            "POST", _make_path(index, "_flush"), params=params
+            "POST", _make_path(index, "_flush"), params=params, headers=headers
         )
 
     @query_params(
         "include_type_name", "master_timeout", "timeout", "wait_for_active_shards"
     )
-    def create(self, index, body=None, params=None):
+    def create(self, index, body=None, params=None, headers=None):
         """
         Creates an index with optional settings and mappings.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-create-index.html>`_
@@ -97,11 +101,11 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path(index), params=params, body=body
+            "PUT", _make_path(index), params=params, headers=headers, body=body
         )
 
     @query_params("master_timeout", "timeout", "wait_for_active_shards")
-    def clone(self, index, target, body=None, params=None):
+    def clone(self, index, target, body=None, params=None, headers=None):
         """
         Clones an index
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-clone-index.html>`_
@@ -120,7 +124,11 @@ class IndicesClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path(index, "_clone", target), params=params, body=body
+            "PUT",
+            _make_path(index, "_clone", target),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -133,7 +141,7 @@ class IndicesClient(NamespacedClient):
         "local",
         "master_timeout",
     )
-    def get(self, index, params=None):
+    def get(self, index, params=None, headers=None):
         """
         Returns information about one or more indices.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-get-index.html>`_
@@ -159,7 +167,9 @@ class IndicesClient(NamespacedClient):
         if index in SKIP_IN_PATH:
             raise ValueError("Empty value passed for a required argument 'index'.")
 
-        return self.transport.perform_request("GET", _make_path(index), params=params)
+        return self.transport.perform_request(
+            "GET", _make_path(index), params=params, headers=headers
+        )
 
     @query_params(
         "allow_no_indices",
@@ -169,7 +179,7 @@ class IndicesClient(NamespacedClient):
         "timeout",
         "wait_for_active_shards",
     )
-    def open(self, index, params=None):
+    def open(self, index, params=None, headers=None):
         """
         Opens an index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-open-close.html>`_
@@ -192,7 +202,7 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(index, "_open"), params=params
+            "POST", _make_path(index, "_open"), params=params, headers=headers
         )
 
     @query_params(
@@ -203,7 +213,7 @@ class IndicesClient(NamespacedClient):
         "timeout",
         "wait_for_active_shards",
     )
-    def close(self, index, params=None):
+    def close(self, index, params=None, headers=None):
         """
         Closes an index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-open-close.html>`_
@@ -226,7 +236,7 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(index, "_close"), params=params
+            "POST", _make_path(index, "_close"), params=params, headers=headers
         )
 
     @query_params(
@@ -236,7 +246,7 @@ class IndicesClient(NamespacedClient):
         "master_timeout",
         "timeout",
     )
-    def delete(self, index, params=None):
+    def delete(self, index, params=None, headers=None):
         """
         Deletes an index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-delete-index.html>`_
@@ -257,7 +267,7 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path(index), params=params
+            "DELETE", _make_path(index), params=params, headers=headers
         )
 
     @query_params(
@@ -268,7 +278,7 @@ class IndicesClient(NamespacedClient):
         "include_defaults",
         "local",
     )
-    def exists(self, index, params=None):
+    def exists(self, index, params=None, headers=None):
         """
         Returns information about whether a particular index exists.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-exists.html>`_
@@ -291,10 +301,12 @@ class IndicesClient(NamespacedClient):
         if index in SKIP_IN_PATH:
             raise ValueError("Empty value passed for a required argument 'index'.")
 
-        return self.transport.perform_request("HEAD", _make_path(index), params=params)
+        return self.transport.perform_request(
+            "HEAD", _make_path(index), params=params, headers=headers
+        )
 
     @query_params("allow_no_indices", "expand_wildcards", "ignore_unavailable", "local")
-    def exists_type(self, index, doc_type, params=None):
+    def exists_type(self, index, doc_type, params=None, headers=None):
         """
         Returns information about whether a particular document type exists.
         (DEPRECATED)
@@ -319,7 +331,10 @@ class IndicesClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "HEAD", _make_path(index, "_mapping", doc_type), params=params
+            "HEAD",
+            _make_path(index, "_mapping", doc_type),
+            params=params,
+            headers=headers,
         )
 
     @query_params(
@@ -330,7 +345,7 @@ class IndicesClient(NamespacedClient):
         "master_timeout",
         "timeout",
     )
-    def put_mapping(self, body, index=None, doc_type=None, params=None):
+    def put_mapping(self, body, index=None, doc_type=None, params=None, headers=None):
         """
         Updates the index mappings.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-put-mapping.html>`_
@@ -360,7 +375,11 @@ class IndicesClient(NamespacedClient):
             index = "_all"
 
         return self.transport.perform_request(
-            "PUT", _make_path(index, doc_type, "_mapping"), params=params, body=body
+            "PUT",
+            _make_path(index, doc_type, "_mapping"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -371,7 +390,7 @@ class IndicesClient(NamespacedClient):
         "local",
         "master_timeout",
     )
-    def get_mapping(self, index=None, doc_type=None, params=None):
+    def get_mapping(self, index=None, doc_type=None, params=None, headers=None):
         """
         Returns mappings for one or more indices.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-get-mapping.html>`_
@@ -393,7 +412,10 @@ class IndicesClient(NamespacedClient):
         :arg master_timeout: Specify timeout for connection to master
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_mapping", doc_type), params=params
+            "GET",
+            _make_path(index, "_mapping", doc_type),
+            params=params,
+            headers=headers,
         )
 
     @query_params(
@@ -404,7 +426,9 @@ class IndicesClient(NamespacedClient):
         "include_type_name",
         "local",
     )
-    def get_field_mapping(self, fields, index=None, doc_type=None, params=None):
+    def get_field_mapping(
+        self, fields, index=None, doc_type=None, params=None, headers=None
+    ):
         """
         Returns mapping for one or more fields.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-get-field-mapping.html>`_
@@ -434,10 +458,11 @@ class IndicesClient(NamespacedClient):
             "GET",
             _make_path(index, "_mapping", doc_type, "field", fields),
             params=params,
+            headers=headers,
         )
 
     @query_params("master_timeout", "timeout")
-    def put_alias(self, index, name, body=None, params=None):
+    def put_alias(self, index, name, body=None, params=None, headers=None):
         """
         Creates or updates an alias.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-aliases.html>`_
@@ -456,11 +481,15 @@ class IndicesClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path(index, "_alias", name), params=params, body=body
+            "PUT",
+            _make_path(index, "_alias", name),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("allow_no_indices", "expand_wildcards", "ignore_unavailable", "local")
-    def exists_alias(self, name, index=None, params=None):
+    def exists_alias(self, name, index=None, params=None, headers=None):
         """
         Returns information about whether a particular alias exists.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-aliases.html>`_
@@ -483,11 +512,11 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "HEAD", _make_path(index, "_alias", name), params=params
+            "HEAD", _make_path(index, "_alias", name), params=params, headers=headers
         )
 
     @query_params("allow_no_indices", "expand_wildcards", "ignore_unavailable", "local")
-    def get_alias(self, index=None, name=None, params=None):
+    def get_alias(self, index=None, name=None, params=None, headers=None):
         """
         Returns an alias.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-aliases.html>`_
@@ -507,11 +536,11 @@ class IndicesClient(NamespacedClient):
             from master node (default: false)
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_alias", name), params=params
+            "GET", _make_path(index, "_alias", name), params=params, headers=headers
         )
 
     @query_params("master_timeout", "timeout")
-    def update_aliases(self, body, params=None):
+    def update_aliases(self, body, params=None, headers=None):
         """
         Updates index aliases.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-aliases.html>`_
@@ -524,11 +553,11 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "POST", "/_aliases", params=params, body=body
+            "POST", "/_aliases", params=params, headers=headers, body=body
         )
 
     @query_params("master_timeout", "timeout")
-    def delete_alias(self, index, name, params=None):
+    def delete_alias(self, index, name, params=None, headers=None):
         """
         Deletes an alias.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-aliases.html>`_
@@ -545,7 +574,7 @@ class IndicesClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path(index, "_alias", name), params=params
+            "DELETE", _make_path(index, "_alias", name), params=params, headers=headers
         )
 
     @query_params(
@@ -556,7 +585,7 @@ class IndicesClient(NamespacedClient):
         "order",
         "timeout",
     )
-    def put_template(self, name, body, params=None):
+    def put_template(self, name, body, params=None, headers=None):
         """
         Creates or updates an index template.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-templates.html>`_
@@ -580,11 +609,15 @@ class IndicesClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_template", name), params=params, body=body
+            "PUT",
+            _make_path("_template", name),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("flat_settings", "local", "master_timeout")
-    def exists_template(self, name, params=None):
+    def exists_template(self, name, params=None, headers=None):
         """
         Returns information about whether a particular index template exists.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-templates.html>`_
@@ -601,11 +634,11 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "HEAD", _make_path("_template", name), params=params
+            "HEAD", _make_path("_template", name), params=params, headers=headers
         )
 
     @query_params("flat_settings", "include_type_name", "local", "master_timeout")
-    def get_template(self, name=None, params=None):
+    def get_template(self, name=None, params=None, headers=None):
         """
         Returns an index template.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-templates.html>`_
@@ -621,11 +654,11 @@ class IndicesClient(NamespacedClient):
             to master node
         """
         return self.transport.perform_request(
-            "GET", _make_path("_template", name), params=params
+            "GET", _make_path("_template", name), params=params, headers=headers
         )
 
     @query_params("master_timeout", "timeout")
-    def delete_template(self, name, params=None):
+    def delete_template(self, name, params=None, headers=None):
         """
         Deletes an index template.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-templates.html>`_
@@ -638,7 +671,7 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_template", name), params=params
+            "DELETE", _make_path("_template", name), params=params, headers=headers
         )
 
     @query_params(
@@ -650,7 +683,7 @@ class IndicesClient(NamespacedClient):
         "local",
         "master_timeout",
     )
-    def get_settings(self, index=None, name=None, params=None):
+    def get_settings(self, index=None, name=None, params=None, headers=None):
         """
         Returns settings for one or more indices.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-get-settings.html>`_
@@ -675,7 +708,7 @@ class IndicesClient(NamespacedClient):
         :arg master_timeout: Specify timeout for connection to master
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_settings", name), params=params
+            "GET", _make_path(index, "_settings", name), params=params, headers=headers
         )
 
     @query_params(
@@ -687,7 +720,7 @@ class IndicesClient(NamespacedClient):
         "preserve_existing",
         "timeout",
     )
-    def put_settings(self, body, index=None, params=None):
+    def put_settings(self, body, index=None, params=None, headers=None):
         """
         Updates the index settings.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-update-settings.html>`_
@@ -715,7 +748,11 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path(index, "_settings"), params=params, body=body
+            "PUT",
+            _make_path(index, "_settings"),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -730,7 +767,7 @@ class IndicesClient(NamespacedClient):
         "level",
         "types",
     )
-    def stats(self, index=None, metric=None, params=None):
+    def stats(self, index=None, metric=None, params=None, headers=None):
         """
         Provides statistics on operations happening in an index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-stats.html>`_
@@ -767,13 +804,13 @@ class IndicesClient(NamespacedClient):
             `indexing` index metric
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_stats", metric), params=params
+            "GET", _make_path(index, "_stats", metric), params=params, headers=headers
         )
 
     @query_params(
         "allow_no_indices", "expand_wildcards", "ignore_unavailable", "verbose"
     )
-    def segments(self, index=None, params=None):
+    def segments(self, index=None, params=None, headers=None):
         """
         Provides low-level information about segments in a Lucene index.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-segments.html>`_
@@ -791,7 +828,7 @@ class IndicesClient(NamespacedClient):
         :arg verbose: Includes detailed memory usage by Lucene.
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_segments"), params=params
+            "GET", _make_path(index, "_segments"), params=params, headers=headers
         )
 
     @query_params(
@@ -808,7 +845,9 @@ class IndicesClient(NamespacedClient):
         "q",
         "rewrite",
     )
-    def validate_query(self, body=None, index=None, doc_type=None, params=None):
+    def validate_query(
+        self, body=None, index=None, doc_type=None, params=None, headers=None
+    ):
         """
         Allows a user to validate a potentially expensive query without executing it.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/search-validate.html>`_
@@ -848,6 +887,7 @@ class IndicesClient(NamespacedClient):
             "GET",
             _make_path(index, doc_type, "_validate", "query"),
             params=params,
+            headers=headers,
             body=body,
         )
 
@@ -860,7 +900,7 @@ class IndicesClient(NamespacedClient):
         "query",
         "request",
     )
-    def clear_cache(self, index=None, params=None):
+    def clear_cache(self, index=None, params=None, headers=None):
         """
         Clears all or specific caches for one or more indices.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-clearcache.html>`_
@@ -884,11 +924,11 @@ class IndicesClient(NamespacedClient):
         :arg request: Clear request cache
         """
         return self.transport.perform_request(
-            "POST", _make_path(index, "_cache", "clear"), params=params
+            "POST", _make_path(index, "_cache", "clear"), params=params, headers=headers
         )
 
     @query_params("active_only", "detailed")
-    def recovery(self, index=None, params=None):
+    def recovery(self, index=None, params=None, headers=None):
         """
         Returns information about ongoing index shard recoveries.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-recovery.html>`_
@@ -901,7 +941,7 @@ class IndicesClient(NamespacedClient):
             shard recovery
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_recovery"), params=params
+            "GET", _make_path(index, "_recovery"), params=params, headers=headers
         )
 
     @query_params(
@@ -911,7 +951,7 @@ class IndicesClient(NamespacedClient):
         "only_ancient_segments",
         "wait_for_completion",
     )
-    def upgrade(self, index=None, params=None):
+    def upgrade(self, index=None, params=None, headers=None):
         """
         The _upgrade API is no longer useful and will be removed.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-upgrade.html>`_
@@ -932,11 +972,11 @@ class IndicesClient(NamespacedClient):
             block until the all segments are upgraded (default: false)
         """
         return self.transport.perform_request(
-            "POST", _make_path(index, "_upgrade"), params=params
+            "POST", _make_path(index, "_upgrade"), params=params, headers=headers
         )
 
     @query_params("allow_no_indices", "expand_wildcards", "ignore_unavailable")
-    def get_upgrade(self, index=None, params=None):
+    def get_upgrade(self, index=None, params=None, headers=None):
         """
         The _upgrade API is no longer useful and will be removed.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-upgrade.html>`_
@@ -953,11 +993,11 @@ class IndicesClient(NamespacedClient):
             should be ignored when unavailable (missing or closed)
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_upgrade"), params=params
+            "GET", _make_path(index, "_upgrade"), params=params, headers=headers
         )
 
     @query_params("allow_no_indices", "expand_wildcards", "ignore_unavailable")
-    def flush_synced(self, index=None, params=None):
+    def flush_synced(self, index=None, params=None, headers=None):
         """
         Performs a synced flush operation on one or more indices.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-synced-flush-api.html>`_
@@ -974,13 +1014,16 @@ class IndicesClient(NamespacedClient):
             should be ignored when unavailable (missing or closed)
         """
         return self.transport.perform_request(
-            "POST", _make_path(index, "_flush", "synced"), params=params
+            "POST",
+            _make_path(index, "_flush", "synced"),
+            params=params,
+            headers=headers,
         )
 
     @query_params(
         "allow_no_indices", "expand_wildcards", "ignore_unavailable", "status"
     )
-    def shard_stores(self, index=None, params=None):
+    def shard_stores(self, index=None, params=None, headers=None):
         """
         Provides store information for shard copies of indices.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-shards-stores.html>`_
@@ -1000,7 +1043,7 @@ class IndicesClient(NamespacedClient):
             red, all
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_shard_stores"), params=params
+            "GET", _make_path(index, "_shard_stores"), params=params, headers=headers
         )
 
     @query_params(
@@ -1011,7 +1054,7 @@ class IndicesClient(NamespacedClient):
         "max_num_segments",
         "only_expunge_deletes",
     )
-    def forcemerge(self, index=None, params=None):
+    def forcemerge(self, index=None, params=None, headers=None):
         """
         Performs the force merge operation on one or more indices.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-forcemerge.html>`_
@@ -1034,13 +1077,13 @@ class IndicesClient(NamespacedClient):
             only expunge deleted documents
         """
         return self.transport.perform_request(
-            "POST", _make_path(index, "_forcemerge"), params=params
+            "POST", _make_path(index, "_forcemerge"), params=params, headers=headers
         )
 
     @query_params(
         "copy_settings", "master_timeout", "timeout", "wait_for_active_shards"
     )
-    def shrink(self, index, target, body=None, params=None):
+    def shrink(self, index, target, body=None, params=None, headers=None):
         """
         Allow to shrink an existing index into a new index with fewer primary shards.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-shrink-index.html>`_
@@ -1061,13 +1104,17 @@ class IndicesClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path(index, "_shrink", target), params=params, body=body
+            "PUT",
+            _make_path(index, "_shrink", target),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
         "copy_settings", "master_timeout", "timeout", "wait_for_active_shards"
     )
-    def split(self, index, target, body=None, params=None):
+    def split(self, index, target, body=None, params=None, headers=None):
         """
         Allows you to split an existing index into a new index with more primary
         shards.
@@ -1089,7 +1136,11 @@ class IndicesClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path(index, "_split", target), params=params, body=body
+            "PUT",
+            _make_path(index, "_split", target),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -1099,7 +1150,7 @@ class IndicesClient(NamespacedClient):
         "timeout",
         "wait_for_active_shards",
     )
-    def rollover(self, alias, body=None, new_index=None, params=None):
+    def rollover(self, alias, body=None, new_index=None, params=None, headers=None):
         """
         Updates an alias to point to a new index when the existing index is considered
         to be too large or too old.
@@ -1124,7 +1175,11 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'alias'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(alias, "_rollover", new_index), params=params, body=body
+            "POST",
+            _make_path(alias, "_rollover", new_index),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params(
@@ -1135,7 +1190,7 @@ class IndicesClient(NamespacedClient):
         "timeout",
         "wait_for_active_shards",
     )
-    def freeze(self, index, params=None):
+    def freeze(self, index, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/frozen.html>`_
 
@@ -1157,7 +1212,7 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(index, "_freeze"), params=params
+            "POST", _make_path(index, "_freeze"), params=params, headers=headers
         )
 
     @query_params(
@@ -1168,7 +1223,7 @@ class IndicesClient(NamespacedClient):
         "timeout",
         "wait_for_active_shards",
     )
-    def unfreeze(self, index, params=None):
+    def unfreeze(self, index, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/frozen.html>`_
 
@@ -1190,11 +1245,11 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "POST", _make_path(index, "_unfreeze"), params=params
+            "POST", _make_path(index, "_unfreeze"), params=params, headers=headers
         )
 
     @query_params("allow_no_indices", "expand_wildcards", "ignore_unavailable")
-    def reload_search_analyzers(self, index, params=None):
+    def reload_search_analyzers(self, index, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-reload-analyzers.html>`_
 
@@ -1213,5 +1268,8 @@ class IndicesClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "GET", _make_path(index, "_reload_search_analyzers"), params=params
+            "GET",
+            _make_path(index, "_reload_search_analyzers"),
+            params=params,
+            headers=headers,
         )
diff --git a/elasticsearch/client/ingest.py b/elasticsearch/client/ingest.py
index 0ef5af6d..09ad3efa 100644
--- a/elasticsearch/client/ingest.py
+++ b/elasticsearch/client/ingest.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class IngestClient(NamespacedClient):
     @query_params("master_timeout")
-    def get_pipeline(self, id=None, params=None):
+    def get_pipeline(self, id=None, params=None, headers=None):
         """
         Returns a pipeline.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/get-pipeline-api.html>`_
@@ -14,11 +14,11 @@ class IngestClient(NamespacedClient):
             to master node
         """
         return self.transport.perform_request(
-            "GET", _make_path("_ingest", "pipeline", id), params=params
+            "GET", _make_path("_ingest", "pipeline", id), params=params, headers=headers
         )
 
     @query_params("master_timeout", "timeout")
-    def put_pipeline(self, id, body, params=None):
+    def put_pipeline(self, id, body, params=None, headers=None):
         """
         Creates or updates a pipeline.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/put-pipeline-api.html>`_
@@ -34,11 +34,15 @@ class IngestClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_ingest", "pipeline", id), params=params, body=body
+            "PUT",
+            _make_path("_ingest", "pipeline", id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("master_timeout", "timeout")
-    def delete_pipeline(self, id, params=None):
+    def delete_pipeline(self, id, params=None, headers=None):
         """
         Deletes a pipeline.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/delete-pipeline-api.html>`_
@@ -52,11 +56,14 @@ class IngestClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_ingest", "pipeline", id), params=params
+            "DELETE",
+            _make_path("_ingest", "pipeline", id),
+            params=params,
+            headers=headers,
         )
 
     @query_params("verbose")
-    def simulate(self, body, id=None, params=None):
+    def simulate(self, body, id=None, params=None, headers=None):
         """
         Allows to simulate a pipeline with example documents.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/simulate-pipeline-api.html>`_
@@ -73,16 +80,17 @@ class IngestClient(NamespacedClient):
             "GET",
             _make_path("_ingest", "pipeline", id, "_simulate"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def processor_grok(self, params=None):
+    def processor_grok(self, params=None, headers=None):
         """
         Returns a list of the built-in patterns.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/grok-processor.html#grok-processor-rest-get>`_
 
         """
         return self.transport.perform_request(
-            "GET", "/_ingest/processor/grok", params=params
+            "GET", "/_ingest/processor/grok", params=params, headers=headers
         )
diff --git a/elasticsearch/client/license.py b/elasticsearch/client/license.py
index b3d5384b..0b33f0c8 100644
--- a/elasticsearch/client/license.py
+++ b/elasticsearch/client/license.py
@@ -3,45 +3,49 @@ from .utils import NamespacedClient, query_params
 
 class LicenseClient(NamespacedClient):
     @query_params()
-    def delete(self, params=None):
+    def delete(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/delete-license.html>`_
 
         """
-        return self.transport.perform_request("DELETE", "/_license", params=params)
+        return self.transport.perform_request(
+            "DELETE", "/_license", params=params, headers=headers
+        )
 
     @query_params("local")
-    def get(self, params=None):
+    def get(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/get-license.html>`_
 
         :arg local: Return local information, do not retrieve the state
             from master node (default: false)
         """
-        return self.transport.perform_request("GET", "/_license", params=params)
+        return self.transport.perform_request(
+            "GET", "/_license", params=params, headers=headers
+        )
 
     @query_params()
-    def get_basic_status(self, params=None):
+    def get_basic_status(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/get-basic-status.html>`_
 
         """
         return self.transport.perform_request(
-            "GET", "/_license/basic_status", params=params
+            "GET", "/_license/basic_status", params=params, headers=headers
         )
 
     @query_params()
-    def get_trial_status(self, params=None):
+    def get_trial_status(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/get-trial-status.html>`_
 
         """
         return self.transport.perform_request(
-            "GET", "/_license/trial_status", params=params
+            "GET", "/_license/trial_status", params=params, headers=headers
         )
 
     @query_params("acknowledge")
-    def post(self, body=None, params=None):
+    def post(self, body=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/update-license.html>`_
 
@@ -50,11 +54,11 @@ class LicenseClient(NamespacedClient):
             messages (default: false)
         """
         return self.transport.perform_request(
-            "PUT", "/_license", params=params, body=body
+            "PUT", "/_license", params=params, headers=headers, body=body
         )
 
     @query_params("acknowledge")
-    def post_start_basic(self, params=None):
+    def post_start_basic(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/start-basic.html>`_
 
@@ -62,11 +66,11 @@ class LicenseClient(NamespacedClient):
             messages (default: false)
         """
         return self.transport.perform_request(
-            "POST", "/_license/start_basic", params=params
+            "POST", "/_license/start_basic", params=params, headers=headers
         )
 
     @query_params("acknowledge", "doc_type")
-    def post_start_trial(self, params=None):
+    def post_start_trial(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/start-trial.html>`_
 
@@ -80,5 +84,5 @@ class LicenseClient(NamespacedClient):
             params["type"] = params.pop("doc_type")
 
         return self.transport.perform_request(
-            "POST", "/_license/start_trial", params=params
+            "POST", "/_license/start_trial", params=params, headers=headers
         )
diff --git a/elasticsearch/client/migration.py b/elasticsearch/client/migration.py
index e8a2fe44..3e888cf6 100644
--- a/elasticsearch/client/migration.py
+++ b/elasticsearch/client/migration.py
@@ -3,12 +3,15 @@ from .utils import NamespacedClient, query_params, _make_path
 
 class MigrationClient(NamespacedClient):
     @query_params()
-    def deprecations(self, index=None, params=None):
+    def deprecations(self, index=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/migration-api-deprecation.html>`_
 
         :arg index: Index pattern
         """
         return self.transport.perform_request(
-            "GET", _make_path(index, "_migration", "deprecations"), params=params
+            "GET",
+            _make_path(index, "_migration", "deprecations"),
+            params=params,
+            headers=headers,
         )
diff --git a/elasticsearch/client/ml.py b/elasticsearch/client/ml.py
index 2a79287a..0c1c6058 100644
--- a/elasticsearch/client/ml.py
+++ b/elasticsearch/client/ml.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH, _bu
 
 class MlClient(NamespacedClient):
     @query_params("allow_no_jobs", "force", "timeout")
-    def close_job(self, job_id, body=None, params=None):
+    def close_job(self, job_id, body=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-close-job.html>`_
 
@@ -23,11 +23,12 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "anomaly_detectors", job_id, "_close"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def delete_calendar(self, calendar_id, params=None):
+    def delete_calendar(self, calendar_id, params=None, headers=None):
         """
 
         :arg calendar_id: The ID of the calendar to delete
@@ -38,11 +39,14 @@ class MlClient(NamespacedClient):
             )
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_ml", "calendars", calendar_id), params=params
+            "DELETE",
+            _make_path("_ml", "calendars", calendar_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def delete_calendar_event(self, calendar_id, event_id, params=None):
+    def delete_calendar_event(self, calendar_id, event_id, params=None, headers=None):
         """
 
         :arg calendar_id: The ID of the calendar to modify
@@ -56,10 +60,11 @@ class MlClient(NamespacedClient):
             "DELETE",
             _make_path("_ml", "calendars", calendar_id, "events", event_id),
             params=params,
+            headers=headers,
         )
 
     @query_params()
-    def delete_calendar_job(self, calendar_id, job_id, params=None):
+    def delete_calendar_job(self, calendar_id, job_id, params=None, headers=None):
         """
 
         :arg calendar_id: The ID of the calendar to modify
@@ -73,10 +78,11 @@ class MlClient(NamespacedClient):
             "DELETE",
             _make_path("_ml", "calendars", calendar_id, "jobs", job_id),
             params=params,
+            headers=headers,
         )
 
     @query_params("force")
-    def delete_datafeed(self, datafeed_id, params=None):
+    def delete_datafeed(self, datafeed_id, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-delete-datafeed.html>`_
 
@@ -89,20 +95,23 @@ class MlClient(NamespacedClient):
             )
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_ml", "datafeeds", datafeed_id), params=params
+            "DELETE",
+            _make_path("_ml", "datafeeds", datafeed_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def delete_expired_data(self, params=None):
+    def delete_expired_data(self, params=None, headers=None):
         """
 
         """
         return self.transport.perform_request(
-            "DELETE", "/_ml/_delete_expired_data", params=params
+            "DELETE", "/_ml/_delete_expired_data", params=params, headers=headers
         )
 
     @query_params()
-    def delete_filter(self, filter_id, params=None):
+    def delete_filter(self, filter_id, params=None, headers=None):
         """
 
         :arg filter_id: The ID of the filter to delete
@@ -111,11 +120,14 @@ class MlClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'filter_id'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_ml", "filters", filter_id), params=params
+            "DELETE",
+            _make_path("_ml", "filters", filter_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params("allow_no_forecasts", "timeout")
-    def delete_forecast(self, job_id, forecast_id=None, params=None):
+    def delete_forecast(self, job_id, forecast_id=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-delete-forecast.html>`_
 
@@ -134,10 +146,11 @@ class MlClient(NamespacedClient):
             "DELETE",
             _make_path("_ml", "anomaly_detectors", job_id, "_forecast", forecast_id),
             params=params,
+            headers=headers,
         )
 
     @query_params("force", "wait_for_completion")
-    def delete_job(self, job_id, params=None):
+    def delete_job(self, job_id, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-delete-job.html>`_
 
@@ -150,11 +163,14 @@ class MlClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'job_id'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_ml", "anomaly_detectors", job_id), params=params
+            "DELETE",
+            _make_path("_ml", "anomaly_detectors", job_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def delete_model_snapshot(self, job_id, snapshot_id, params=None):
+    def delete_model_snapshot(self, job_id, snapshot_id, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-delete-snapshot.html>`_
 
@@ -171,6 +187,7 @@ class MlClient(NamespacedClient):
                 "_ml", "anomaly_detectors", job_id, "model_snapshots", snapshot_id
             ),
             params=params,
+            headers=headers,
         )
 
     @query_params(
@@ -189,7 +206,7 @@ class MlClient(NamespacedClient):
         "timestamp_field",
         "timestamp_format",
     )
-    def find_file_structure(self, body, params=None):
+    def find_file_structure(self, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-find-file-structure.html>`_
 
@@ -231,11 +248,15 @@ class MlClient(NamespacedClient):
 
         body = _bulk_body(self.transport.serializer, body)
         return self.transport.perform_request(
-            "POST", "/_ml/find_file_structure", params=params, body=body
+            "POST",
+            "/_ml/find_file_structure",
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("advance_time", "calc_interim", "end", "skip_time", "start")
-    def flush_job(self, job_id, body=None, params=None):
+    def flush_job(self, job_id, body=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-flush-job.html>`_
 
@@ -259,11 +280,12 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "anomaly_detectors", job_id, "_flush"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("duration", "expires_in")
-    def forecast(self, job_id, params=None):
+    def forecast(self, job_id, params=None, headers=None):
         """
 
         :arg job_id: The ID of the job to forecast for
@@ -278,6 +300,7 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "anomaly_detectors", job_id, "_forecast"),
             params=params,
+            headers=headers,
         )
 
     @query_params(
@@ -291,7 +314,7 @@ class MlClient(NamespacedClient):
         "sort",
         "start",
     )
-    def get_buckets(self, job_id, body=None, timestamp=None, params=None):
+    def get_buckets(self, job_id, body=None, timestamp=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-bucket.html>`_
 
@@ -322,11 +345,12 @@ class MlClient(NamespacedClient):
                 "_ml", "anomaly_detectors", job_id, "results", "buckets", timestamp
             ),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("end", "from_", "job_id", "size", "start")
-    def get_calendar_events(self, calendar_id, params=None):
+    def get_calendar_events(self, calendar_id, params=None, headers=None):
         """
 
         :arg calendar_id: The ID of the calendar containing the events
@@ -347,11 +371,14 @@ class MlClient(NamespacedClient):
             )
 
         return self.transport.perform_request(
-            "GET", _make_path("_ml", "calendars", calendar_id, "events"), params=params
+            "GET",
+            _make_path("_ml", "calendars", calendar_id, "events"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("from_", "size")
-    def get_calendars(self, body=None, calendar_id=None, params=None):
+    def get_calendars(self, body=None, calendar_id=None, params=None, headers=None):
         """
 
         :arg body: The from and size parameters optionally sent in the
@@ -365,11 +392,17 @@ class MlClient(NamespacedClient):
             params["from"] = params.pop("from_")
 
         return self.transport.perform_request(
-            "GET", _make_path("_ml", "calendars", calendar_id), params=params, body=body
+            "GET",
+            _make_path("_ml", "calendars", calendar_id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("from_", "size")
-    def get_categories(self, job_id, body=None, category_id=None, params=None):
+    def get_categories(
+        self, job_id, body=None, category_id=None, params=None, headers=None
+    ):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-category.html>`_
 
@@ -393,11 +426,12 @@ class MlClient(NamespacedClient):
                 "_ml", "anomaly_detectors", job_id, "results", "categories", category_id
             ),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("allow_no_datafeeds")
-    def get_datafeed_stats(self, datafeed_id=None, params=None):
+    def get_datafeed_stats(self, datafeed_id=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-datafeed-stats.html>`_
 
@@ -407,11 +441,14 @@ class MlClient(NamespacedClient):
             datafeeds have been specified)
         """
         return self.transport.perform_request(
-            "GET", _make_path("_ml", "datafeeds", datafeed_id, "_stats"), params=params
+            "GET",
+            _make_path("_ml", "datafeeds", datafeed_id, "_stats"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("allow_no_datafeeds")
-    def get_datafeeds(self, datafeed_id=None, params=None):
+    def get_datafeeds(self, datafeed_id=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-datafeed.html>`_
 
@@ -421,11 +458,14 @@ class MlClient(NamespacedClient):
             datafeeds have been specified)
         """
         return self.transport.perform_request(
-            "GET", _make_path("_ml", "datafeeds", datafeed_id), params=params
+            "GET",
+            _make_path("_ml", "datafeeds", datafeed_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params("from_", "size")
-    def get_filters(self, filter_id=None, params=None):
+    def get_filters(self, filter_id=None, params=None, headers=None):
         """
 
         :arg filter_id: The ID of the filter to fetch
@@ -437,7 +477,10 @@ class MlClient(NamespacedClient):
             params["from"] = params.pop("from_")
 
         return self.transport.perform_request(
-            "GET", _make_path("_ml", "filters", filter_id), params=params
+            "GET",
+            _make_path("_ml", "filters", filter_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params(
@@ -450,7 +493,7 @@ class MlClient(NamespacedClient):
         "sort",
         "start",
     )
-    def get_influencers(self, job_id, body=None, params=None):
+    def get_influencers(self, job_id, body=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-influencer.html>`_
 
@@ -478,11 +521,12 @@ class MlClient(NamespacedClient):
             "GET",
             _make_path("_ml", "anomaly_detectors", job_id, "results", "influencers"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("allow_no_jobs")
-    def get_job_stats(self, job_id=None, params=None):
+    def get_job_stats(self, job_id=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-job-stats.html>`_
 
@@ -495,10 +539,11 @@ class MlClient(NamespacedClient):
             "GET",
             _make_path("_ml", "anomaly_detectors", job_id, "_stats"),
             params=params,
+            headers=headers,
         )
 
     @query_params("allow_no_jobs")
-    def get_jobs(self, job_id=None, params=None):
+    def get_jobs(self, job_id=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-job.html>`_
 
@@ -508,11 +553,16 @@ class MlClient(NamespacedClient):
             specified)
         """
         return self.transport.perform_request(
-            "GET", _make_path("_ml", "anomaly_detectors", job_id), params=params
+            "GET",
+            _make_path("_ml", "anomaly_detectors", job_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params("desc", "end", "from_", "size", "sort", "start")
-    def get_model_snapshots(self, job_id, body=None, snapshot_id=None, params=None):
+    def get_model_snapshots(
+        self, job_id, body=None, snapshot_id=None, params=None, headers=None
+    ):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-snapshot.html>`_
 
@@ -541,6 +591,7 @@ class MlClient(NamespacedClient):
                 "_ml", "anomaly_detectors", job_id, "model_snapshots", snapshot_id
             ),
             params=params,
+            headers=headers,
             body=body,
         )
 
@@ -553,7 +604,7 @@ class MlClient(NamespacedClient):
         "start",
         "top_n",
     )
-    def get_overall_buckets(self, job_id, body=None, params=None):
+    def get_overall_buckets(self, job_id, body=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-overall-buckets.html>`_
 
@@ -586,6 +637,7 @@ class MlClient(NamespacedClient):
                 "_ml", "anomaly_detectors", job_id, "results", "overall_buckets"
             ),
             params=params,
+            headers=headers,
             body=body,
         )
 
@@ -599,7 +651,7 @@ class MlClient(NamespacedClient):
         "sort",
         "start",
     )
-    def get_records(self, job_id, body=None, params=None):
+    def get_records(self, job_id, body=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-get-record.html>`_
 
@@ -625,18 +677,21 @@ class MlClient(NamespacedClient):
             "GET",
             _make_path("_ml", "anomaly_detectors", job_id, "results", "records"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def info(self, params=None):
+    def info(self, params=None, headers=None):
         """
 
         """
-        return self.transport.perform_request("GET", "/_ml/info", params=params)
+        return self.transport.perform_request(
+            "GET", "/_ml/info", params=params, headers=headers
+        )
 
     @query_params()
-    def open_job(self, job_id, params=None):
+    def open_job(self, job_id, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-open-job.html>`_
 
@@ -649,10 +704,11 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "anomaly_detectors", job_id, "_open"),
             params=params,
+            headers=headers,
         )
 
     @query_params()
-    def post_calendar_events(self, calendar_id, body, params=None):
+    def post_calendar_events(self, calendar_id, body, params=None, headers=None):
         """
 
         :arg calendar_id: The ID of the calendar to modify
@@ -666,11 +722,12 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "calendars", calendar_id, "events"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("reset_end", "reset_start")
-    def post_data(self, job_id, body, params=None):
+    def post_data(self, job_id, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-post-data.html>`_
 
@@ -690,11 +747,12 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "anomaly_detectors", job_id, "_data"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def preview_datafeed(self, datafeed_id, params=None):
+    def preview_datafeed(self, datafeed_id, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-preview-datafeed.html>`_
 
@@ -709,10 +767,11 @@ class MlClient(NamespacedClient):
             "GET",
             _make_path("_ml", "datafeeds", datafeed_id, "_preview"),
             params=params,
+            headers=headers,
         )
 
     @query_params()
-    def put_calendar(self, calendar_id, body=None, params=None):
+    def put_calendar(self, calendar_id, body=None, params=None, headers=None):
         """
 
         :arg calendar_id: The ID of the calendar to create
@@ -724,11 +783,15 @@ class MlClient(NamespacedClient):
             )
 
         return self.transport.perform_request(
-            "PUT", _make_path("_ml", "calendars", calendar_id), params=params, body=body
+            "PUT",
+            _make_path("_ml", "calendars", calendar_id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def put_calendar_job(self, calendar_id, job_id, params=None):
+    def put_calendar_job(self, calendar_id, job_id, params=None, headers=None):
         """
 
         :arg calendar_id: The ID of the calendar to modify
@@ -742,10 +805,11 @@ class MlClient(NamespacedClient):
             "PUT",
             _make_path("_ml", "calendars", calendar_id, "jobs", job_id),
             params=params,
+            headers=headers,
         )
 
     @query_params()
-    def put_datafeed(self, datafeed_id, body, params=None):
+    def put_datafeed(self, datafeed_id, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-put-datafeed.html>`_
 
@@ -757,11 +821,15 @@ class MlClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_ml", "datafeeds", datafeed_id), params=params, body=body
+            "PUT",
+            _make_path("_ml", "datafeeds", datafeed_id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def put_filter(self, filter_id, body, params=None):
+    def put_filter(self, filter_id, body, params=None, headers=None):
         """
 
         :arg filter_id: The ID of the filter to create
@@ -772,11 +840,15 @@ class MlClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_ml", "filters", filter_id), params=params, body=body
+            "PUT",
+            _make_path("_ml", "filters", filter_id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def put_job(self, job_id, body, params=None):
+    def put_job(self, job_id, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-put-job.html>`_
 
@@ -791,11 +863,14 @@ class MlClient(NamespacedClient):
             "PUT",
             _make_path("_ml", "anomaly_detectors", job_id),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("delete_intervening_results")
-    def revert_model_snapshot(self, job_id, snapshot_id, body=None, params=None):
+    def revert_model_snapshot(
+        self, job_id, snapshot_id, body=None, params=None, headers=None
+    ):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-revert-snapshot.html>`_
 
@@ -820,11 +895,12 @@ class MlClient(NamespacedClient):
                 "_revert",
             ),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("enabled", "timeout")
-    def set_upgrade_mode(self, params=None):
+    def set_upgrade_mode(self, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-set-upgrade-mode.html>`_
 
@@ -834,11 +910,11 @@ class MlClient(NamespacedClient):
             Defaults to 30 seconds
         """
         return self.transport.perform_request(
-            "POST", "/_ml/set_upgrade_mode", params=params
+            "POST", "/_ml/set_upgrade_mode", params=params, headers=headers
         )
 
     @query_params("end", "start", "timeout")
-    def start_datafeed(self, datafeed_id, body=None, params=None):
+    def start_datafeed(self, datafeed_id, body=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-start-datafeed.html>`_
 
@@ -859,11 +935,12 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "datafeeds", datafeed_id, "_start"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("allow_no_datafeeds", "force", "timeout")
-    def stop_datafeed(self, datafeed_id, params=None):
+    def stop_datafeed(self, datafeed_id, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-stop-datafeed.html>`_
 
@@ -881,11 +958,14 @@ class MlClient(NamespacedClient):
             )
 
         return self.transport.perform_request(
-            "POST", _make_path("_ml", "datafeeds", datafeed_id, "_stop"), params=params
+            "POST",
+            _make_path("_ml", "datafeeds", datafeed_id, "_stop"),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def update_datafeed(self, datafeed_id, body, params=None):
+    def update_datafeed(self, datafeed_id, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-update-datafeed.html>`_
 
@@ -900,11 +980,12 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "datafeeds", datafeed_id, "_update"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def update_filter(self, filter_id, body, params=None):
+    def update_filter(self, filter_id, body, params=None, headers=None):
         """
 
         :arg filter_id: The ID of the filter to update
@@ -918,11 +999,12 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "filters", filter_id, "_update"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def update_job(self, job_id, body, params=None):
+    def update_job(self, job_id, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-update-job.html>`_
 
@@ -937,11 +1019,14 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "anomaly_detectors", job_id, "_update"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def update_model_snapshot(self, job_id, snapshot_id, body, params=None):
+    def update_model_snapshot(
+        self, job_id, snapshot_id, body, params=None, headers=None
+    ):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-update-snapshot.html>`_
 
@@ -964,11 +1049,12 @@ class MlClient(NamespacedClient):
                 "_update",
             ),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def validate(self, body, params=None):
+    def validate(self, body, params=None, headers=None):
         """
 
         :arg body: The job config
@@ -977,11 +1063,15 @@ class MlClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "POST", "/_ml/anomaly_detectors/_validate", params=params, body=body
+            "POST",
+            "/_ml/anomaly_detectors/_validate",
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def validate_detector(self, body, params=None):
+    def validate_detector(self, body, params=None, headers=None):
         """
 
         :arg body: The detector
@@ -993,11 +1083,12 @@ class MlClient(NamespacedClient):
             "POST",
             "/_ml/anomaly_detectors/_validate/detector",
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def delete_data_frame_analytics(self, id, params=None):
+    def delete_data_frame_analytics(self, id, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/delete-dfanalytics.html>`_
 
@@ -1007,11 +1098,14 @@ class MlClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_ml", "data_frame", "analytics", id), params=params
+            "DELETE",
+            _make_path("_ml", "data_frame", "analytics", id),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def estimate_memory_usage(self, body, params=None):
+    def estimate_memory_usage(self, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/estimate-memory-usage-dfanalytics.html>`_
 
@@ -1024,11 +1118,12 @@ class MlClient(NamespacedClient):
             "POST",
             "/_ml/data_frame/analytics/_estimate_memory_usage",
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def evaluate_data_frame(self, body, params=None):
+    def evaluate_data_frame(self, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/evaluate-dfanalytics.html>`_
 
@@ -1038,11 +1133,15 @@ class MlClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "POST", "/_ml/data_frame/_evaluate", params=params, body=body
+            "POST",
+            "/_ml/data_frame/_evaluate",
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("allow_no_match", "from_", "size")
-    def get_data_frame_analytics(self, id=None, params=None):
+    def get_data_frame_analytics(self, id=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/get-dfanalytics.html>`_
 
@@ -1059,11 +1158,14 @@ class MlClient(NamespacedClient):
             params["from"] = params.pop("from_")
 
         return self.transport.perform_request(
-            "GET", _make_path("_ml", "data_frame", "analytics", id), params=params
+            "GET",
+            _make_path("_ml", "data_frame", "analytics", id),
+            params=params,
+            headers=headers,
         )
 
     @query_params("allow_no_match", "from_", "size")
-    def get_data_frame_analytics_stats(self, id=None, params=None):
+    def get_data_frame_analytics_stats(self, id=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/get-dfanalytics-stats.html>`_
 
@@ -1083,10 +1185,11 @@ class MlClient(NamespacedClient):
             "GET",
             _make_path("_ml", "data_frame", "analytics", id, "_stats"),
             params=params,
+            headers=headers,
         )
 
     @query_params()
-    def put_data_frame_analytics(self, id, body, params=None):
+    def put_data_frame_analytics(self, id, body, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/put-dfanalytics.html>`_
 
@@ -1101,11 +1204,12 @@ class MlClient(NamespacedClient):
             "PUT",
             _make_path("_ml", "data_frame", "analytics", id),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("timeout")
-    def start_data_frame_analytics(self, id, body=None, params=None):
+    def start_data_frame_analytics(self, id, body=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/start-dfanalytics.html>`_
 
@@ -1121,11 +1225,12 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "data_frame", "analytics", id, "_start"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("allow_no_match", "force", "timeout")
-    def stop_data_frame_analytics(self, id, body=None, params=None):
+    def stop_data_frame_analytics(self, id, body=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/stop-dfanalytics.html>`_
 
@@ -1146,5 +1251,6 @@ class MlClient(NamespacedClient):
             "POST",
             _make_path("_ml", "data_frame", "analytics", id, "_stop"),
             params=params,
+            headers=headers,
             body=body,
         )
diff --git a/elasticsearch/client/monitoring.py b/elasticsearch/client/monitoring.py
index b463609b..3be40eac 100644
--- a/elasticsearch/client/monitoring.py
+++ b/elasticsearch/client/monitoring.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH, _bu
 
 class MonitoringClient(NamespacedClient):
     @query_params("interval", "system_api_version", "system_id")
-    def bulk(self, body, doc_type=None, params=None):
+    def bulk(self, body, doc_type=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/es-monitoring.html>`_
 
@@ -24,5 +24,6 @@ class MonitoringClient(NamespacedClient):
             "POST",
             _make_path("_monitoring", doc_type, "bulk"),
             params=params,
+            headers=headers,
             body=body,
         )
diff --git a/elasticsearch/client/nodes.py b/elasticsearch/client/nodes.py
index 8b160b71..61b01a6e 100644
--- a/elasticsearch/client/nodes.py
+++ b/elasticsearch/client/nodes.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path
 
 class NodesClient(NamespacedClient):
     @query_params("timeout")
-    def reload_secure_settings(self, node_id=None, params=None):
+    def reload_secure_settings(self, node_id=None, params=None, headers=None):
         """
         Reloads secure settings.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/secure-settings.html#reloadable-secure-settings>`_
@@ -17,10 +17,11 @@ class NodesClient(NamespacedClient):
             "POST",
             _make_path("_nodes", node_id, "reload_secure_settings"),
             params=params,
+            headers=headers,
         )
 
     @query_params("flat_settings", "timeout")
-    def info(self, node_id=None, metric=None, params=None):
+    def info(self, node_id=None, metric=None, params=None, headers=None):
         """
         Returns information about nodes in the cluster.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-nodes-info.html>`_
@@ -37,7 +38,7 @@ class NodesClient(NamespacedClient):
         :arg timeout: Explicit operation timeout
         """
         return self.transport.perform_request(
-            "GET", _make_path("_nodes", node_id, metric), params=params
+            "GET", _make_path("_nodes", node_id, metric), params=params, headers=headers
         )
 
     @query_params(
@@ -50,7 +51,9 @@ class NodesClient(NamespacedClient):
         "timeout",
         "types",
     )
-    def stats(self, node_id=None, metric=None, index_metric=None, params=None):
+    def stats(
+        self, node_id=None, metric=None, index_metric=None, params=None, headers=None
+    ):
         """
         Returns statistical information about nodes in the cluster.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-nodes-stats.html>`_
@@ -88,12 +91,13 @@ class NodesClient(NamespacedClient):
             "GET",
             _make_path("_nodes", node_id, "stats", metric, index_metric),
             params=params,
+            headers=headers,
         )
 
     @query_params(
         "doc_type", "ignore_idle_threads", "interval", "snapshots", "threads", "timeout"
     )
-    def hot_threads(self, node_id=None, params=None):
+    def hot_threads(self, node_id=None, params=None, headers=None):
         """
         Returns information about hot threads on each node in the cluster.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-nodes-hot-threads.html>`_
@@ -119,11 +123,14 @@ class NodesClient(NamespacedClient):
             params["type"] = params.pop("doc_type")
 
         return self.transport.perform_request(
-            "GET", _make_path("_nodes", node_id, "hot_threads"), params=params
+            "GET",
+            _make_path("_nodes", node_id, "hot_threads"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("timeout")
-    def usage(self, node_id=None, metric=None, params=None):
+    def usage(self, node_id=None, metric=None, params=None, headers=None):
         """
         Returns low-level information about REST actions usage on nodes.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/cluster-nodes-usage.html>`_
@@ -137,5 +144,8 @@ class NodesClient(NamespacedClient):
         :arg timeout: Explicit operation timeout
         """
         return self.transport.perform_request(
-            "GET", _make_path("_nodes", node_id, "usage", metric), params=params
+            "GET",
+            _make_path("_nodes", node_id, "usage", metric),
+            params=params,
+            headers=headers,
         )
diff --git a/elasticsearch/client/remote.py b/elasticsearch/client/remote.py
index 5be630c1..8590313a 100644
--- a/elasticsearch/client/remote.py
+++ b/elasticsearch/client/remote.py
@@ -3,8 +3,10 @@ from .utils import NamespacedClient, query_params
 
 class RemoteClient(NamespacedClient):
     @query_params()
-    def info(self, params=None):
+    def info(self, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/cluster-remote-info.html>`_
         """
-        return self.transport.perform_request("GET", "/_remote/info", params=params)
+        return self.transport.perform_request(
+            "GET", "/_remote/info", params=params, headers=headers
+        )
diff --git a/elasticsearch/client/rollup.py b/elasticsearch/client/rollup.py
index ecb89ab3..a9b6b9e7 100644
--- a/elasticsearch/client/rollup.py
+++ b/elasticsearch/client/rollup.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class RollupClient(NamespacedClient):
     @query_params()
-    def delete_job(self, id, params=None):
+    def delete_job(self, id, params=None, headers=None):
         """
 
         :arg id: The ID of the job to delete
@@ -12,33 +12,33 @@ class RollupClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_rollup", "job", id), params=params
+            "DELETE", _make_path("_rollup", "job", id), params=params, headers=headers
         )
 
     @query_params()
-    def get_jobs(self, id=None, params=None):
+    def get_jobs(self, id=None, params=None, headers=None):
         """
 
         :arg id: The ID of the job(s) to fetch. Accepts glob patterns,
             or left blank for all jobs
         """
         return self.transport.perform_request(
-            "GET", _make_path("_rollup", "job", id), params=params
+            "GET", _make_path("_rollup", "job", id), params=params, headers=headers
         )
 
     @query_params()
-    def get_rollup_caps(self, id=None, params=None):
+    def get_rollup_caps(self, id=None, params=None, headers=None):
         """
 
         :arg id: The ID of the index to check rollup capabilities on, or
             left blank for all jobs
         """
         return self.transport.perform_request(
-            "GET", _make_path("_rollup", "data", id), params=params
+            "GET", _make_path("_rollup", "data", id), params=params, headers=headers
         )
 
     @query_params()
-    def get_rollup_index_caps(self, index, params=None):
+    def get_rollup_index_caps(self, index, params=None, headers=None):
         """
 
         :arg index: The rollup index or index pattern to obtain rollup
@@ -48,11 +48,11 @@ class RollupClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'index'.")
 
         return self.transport.perform_request(
-            "GET", _make_path(index, "_rollup", "data"), params=params
+            "GET", _make_path(index, "_rollup", "data"), params=params, headers=headers
         )
 
     @query_params()
-    def put_job(self, id, body, params=None):
+    def put_job(self, id, body, params=None, headers=None):
         """
 
         :arg id: The ID of the job to create
@@ -63,11 +63,15 @@ class RollupClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_rollup", "job", id), params=params, body=body
+            "PUT",
+            _make_path("_rollup", "job", id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("rest_total_hits_as_int", "typed_keys")
-    def rollup_search(self, index, body, doc_type=None, params=None):
+    def rollup_search(self, index, body, doc_type=None, params=None, headers=None):
         """
 
         :arg index: The indices or index-pattern(s) (containing rollup
@@ -87,11 +91,12 @@ class RollupClient(NamespacedClient):
             "GET",
             _make_path(index, doc_type, "_rollup_search"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def start_job(self, id, params=None):
+    def start_job(self, id, params=None, headers=None):
         """
 
         :arg id: The ID of the job to start
@@ -100,11 +105,14 @@ class RollupClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "POST", _make_path("_rollup", "job", id, "_start"), params=params
+            "POST",
+            _make_path("_rollup", "job", id, "_start"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("timeout", "wait_for_completion")
-    def stop_job(self, id, params=None):
+    def stop_job(self, id, params=None, headers=None):
         """
 
         :arg id: The ID of the job to stop
@@ -118,5 +126,8 @@ class RollupClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "POST", _make_path("_rollup", "job", id, "_stop"), params=params
+            "POST",
+            _make_path("_rollup", "job", id, "_stop"),
+            params=params,
+            headers=headers,
         )
diff --git a/elasticsearch/client/security.py b/elasticsearch/client/security.py
index 1cd2382d..472c6bd4 100644
--- a/elasticsearch/client/security.py
+++ b/elasticsearch/client/security.py
@@ -3,17 +3,17 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class SecurityClient(NamespacedClient):
     @query_params()
-    def authenticate(self, params=None):
+    def authenticate(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-authenticate.html>`_
 
         """
         return self.transport.perform_request(
-            "GET", "/_security/_authenticate", params=params
+            "GET", "/_security/_authenticate", params=params, headers=headers
         )
 
     @query_params("refresh")
-    def change_password(self, body, username=None, params=None):
+    def change_password(self, body, username=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-change-password.html>`_
 
@@ -32,11 +32,12 @@ class SecurityClient(NamespacedClient):
             "PUT",
             _make_path("_security", "user", username, "_password"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("usernames")
-    def clear_cached_realms(self, realms, params=None):
+    def clear_cached_realms(self, realms, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-clear-cache.html>`_
 
@@ -51,10 +52,11 @@ class SecurityClient(NamespacedClient):
             "POST",
             _make_path("_security", "realm", realms, "_clear_cache"),
             params=params,
+            headers=headers,
         )
 
     @query_params()
-    def clear_cached_roles(self, name, params=None):
+    def clear_cached_roles(self, name, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-clear-role-cache.html>`_
 
@@ -64,11 +66,14 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "POST", _make_path("_security", "role", name, "_clear_cache"), params=params
+            "POST",
+            _make_path("_security", "role", name, "_clear_cache"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("refresh")
-    def create_api_key(self, body, params=None):
+    def create_api_key(self, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-create-api-key.html>`_
 
@@ -82,11 +87,11 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "PUT", "/_security/api_key", params=params, body=body
+            "PUT", "/_security/api_key", params=params, headers=headers, body=body
         )
 
     @query_params("refresh")
-    def delete_privileges(self, application, name, params=None):
+    def delete_privileges(self, application, name, params=None, headers=None):
         """
         `<TODO>`_
 
@@ -105,10 +110,11 @@ class SecurityClient(NamespacedClient):
             "DELETE",
             _make_path("_security", "privilege", application, name),
             params=params,
+            headers=headers,
         )
 
     @query_params("refresh")
-    def delete_role(self, name, params=None):
+    def delete_role(self, name, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-delete-role.html>`_
 
@@ -122,11 +128,14 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_security", "role", name), params=params
+            "DELETE",
+            _make_path("_security", "role", name),
+            params=params,
+            headers=headers,
         )
 
     @query_params("refresh")
-    def delete_role_mapping(self, name, params=None):
+    def delete_role_mapping(self, name, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-delete-role-mapping.html>`_
 
@@ -140,11 +149,14 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'name'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_security", "role_mapping", name), params=params
+            "DELETE",
+            _make_path("_security", "role_mapping", name),
+            params=params,
+            headers=headers,
         )
 
     @query_params("refresh")
-    def delete_user(self, username, params=None):
+    def delete_user(self, username, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-delete-user.html>`_
 
@@ -158,11 +170,14 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'username'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_security", "user", username), params=params
+            "DELETE",
+            _make_path("_security", "user", username),
+            params=params,
+            headers=headers,
         )
 
     @query_params("refresh")
-    def disable_user(self, username, params=None):
+    def disable_user(self, username, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-disable-user.html>`_
 
@@ -176,11 +191,14 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'username'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_security", "user", username, "_disable"), params=params
+            "PUT",
+            _make_path("_security", "user", username, "_disable"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("refresh")
-    def enable_user(self, username, params=None):
+    def enable_user(self, username, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-enable-user.html>`_
 
@@ -194,11 +212,14 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'username'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_security", "user", username, "_enable"), params=params
+            "PUT",
+            _make_path("_security", "user", username, "_enable"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("id", "name", "owner", "realm_name", "username")
-    def get_api_key(self, params=None):
+    def get_api_key(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-get-api-key.html>`_
 
@@ -212,11 +233,11 @@ class SecurityClient(NamespacedClient):
             be retrieved
         """
         return self.transport.perform_request(
-            "GET", "/_security/api_key", params=params
+            "GET", "/_security/api_key", params=params, headers=headers
         )
 
     @query_params()
-    def get_privileges(self, application=None, name=None, params=None):
+    def get_privileges(self, application=None, name=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-get-privileges.html>`_
 
@@ -227,32 +248,36 @@ class SecurityClient(NamespacedClient):
             "GET",
             _make_path("_security", "privilege", application, name),
             params=params,
+            headers=headers,
         )
 
     @query_params()
-    def get_role(self, name=None, params=None):
+    def get_role(self, name=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-get-role.html>`_
 
         :arg name: Role name
         """
         return self.transport.perform_request(
-            "GET", _make_path("_security", "role", name), params=params
+            "GET", _make_path("_security", "role", name), params=params, headers=headers
         )
 
     @query_params()
-    def get_role_mapping(self, name=None, params=None):
+    def get_role_mapping(self, name=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-get-role-mapping.html>`_
 
         :arg name: Role-Mapping name
         """
         return self.transport.perform_request(
-            "GET", _make_path("_security", "role_mapping", name), params=params
+            "GET",
+            _make_path("_security", "role_mapping", name),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def get_token(self, body, params=None):
+    def get_token(self, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-get-token.html>`_
 
@@ -262,32 +287,35 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "POST", "/_security/oauth2/token", params=params, body=body
+            "POST", "/_security/oauth2/token", params=params, headers=headers, body=body
         )
 
     @query_params()
-    def get_user(self, username=None, params=None):
+    def get_user(self, username=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-get-user.html>`_
 
         :arg username: A comma-separated list of usernames
         """
         return self.transport.perform_request(
-            "GET", _make_path("_security", "user", username), params=params
+            "GET",
+            _make_path("_security", "user", username),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def get_user_privileges(self, params=None):
+    def get_user_privileges(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-get-privileges.html>`_
 
         """
         return self.transport.perform_request(
-            "GET", "/_security/user/_privileges", params=params
+            "GET", "/_security/user/_privileges", params=params, headers=headers
         )
 
     @query_params()
-    def has_privileges(self, body, user=None, params=None):
+    def has_privileges(self, body, user=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-has-privileges.html>`_
 
@@ -301,11 +329,12 @@ class SecurityClient(NamespacedClient):
             "GET",
             _make_path("_security", "user", user, "_has_privileges"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def invalidate_api_key(self, body, params=None):
+    def invalidate_api_key(self, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-invalidate-api-key.html>`_
 
@@ -315,11 +344,11 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "DELETE", "/_security/api_key", params=params, body=body
+            "DELETE", "/_security/api_key", params=params, headers=headers, body=body
         )
 
     @query_params()
-    def invalidate_token(self, body, params=None):
+    def invalidate_token(self, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-invalidate-token.html>`_
 
@@ -329,11 +358,15 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "DELETE", "/_security/oauth2/token", params=params, body=body
+            "DELETE",
+            "/_security/oauth2/token",
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("refresh")
-    def put_privileges(self, body, params=None):
+    def put_privileges(self, body, params=None, headers=None):
         """
         `<TODO>`_
 
@@ -347,11 +380,11 @@ class SecurityClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "PUT", "/_security/privilege/", params=params, body=body
+            "PUT", "/_security/privilege/", params=params, headers=headers, body=body
         )
 
     @query_params("refresh")
-    def put_role(self, name, body, params=None):
+    def put_role(self, name, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-put-role.html>`_
 
@@ -367,11 +400,15 @@ class SecurityClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_security", "role", name), params=params, body=body
+            "PUT",
+            _make_path("_security", "role", name),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("refresh")
-    def put_role_mapping(self, name, body, params=None):
+    def put_role_mapping(self, name, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-put-role-mapping.html>`_
 
@@ -390,11 +427,12 @@ class SecurityClient(NamespacedClient):
             "PUT",
             _make_path("_security", "role_mapping", name),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("refresh")
-    def put_user(self, username, body, params=None):
+    def put_user(self, username, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-put-user.html>`_
 
@@ -410,15 +448,19 @@ class SecurityClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_security", "user", username), params=params, body=body
+            "PUT",
+            _make_path("_security", "user", username),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def get_builtin_privileges(self, params=None):
+    def get_builtin_privileges(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-get-builtin-privileges.html>`_
 
         """
         return self.transport.perform_request(
-            "GET", "/_security/privilege/_builtin", params=params
+            "GET", "/_security/privilege/_builtin", params=params, headers=headers
         )
diff --git a/elasticsearch/client/slm.py b/elasticsearch/client/slm.py
index 7e37a7e3..baf80bc5 100644
--- a/elasticsearch/client/slm.py
+++ b/elasticsearch/client/slm.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class SlmClient(NamespacedClient):
     @query_params()
-    def delete_lifecycle(self, policy_id, params=None):
+    def delete_lifecycle(self, policy_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/slm-api-delete.html>`_
 
@@ -14,11 +14,14 @@ class SlmClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'policy_id'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_slm", "policy", policy_id), params=params
+            "DELETE",
+            _make_path("_slm", "policy", policy_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def execute_lifecycle(self, policy_id, params=None):
+    def execute_lifecycle(self, policy_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/slm-api-execute.html>`_
 
@@ -29,21 +32,24 @@ class SlmClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'policy_id'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_slm", "policy", policy_id, "_execute"), params=params
+            "PUT",
+            _make_path("_slm", "policy", policy_id, "_execute"),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def execute_retention(self, params=None):
+    def execute_retention(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/slm-api-execute-retention.html>`_
 
         """
         return self.transport.perform_request(
-            "POST", "/_slm/_execute_retention", params=params
+            "POST", "/_slm/_execute_retention", params=params, headers=headers
         )
 
     @query_params()
-    def get_lifecycle(self, policy_id=None, params=None):
+    def get_lifecycle(self, policy_id=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/slm-api-get.html>`_
 
@@ -51,19 +57,24 @@ class SlmClient(NamespacedClient):
             policies to retrieve
         """
         return self.transport.perform_request(
-            "GET", _make_path("_slm", "policy", policy_id), params=params
+            "GET",
+            _make_path("_slm", "policy", policy_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def get_stats(self, params=None):
+    def get_stats(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/slm-get-stats.html>`_
 
         """
-        return self.transport.perform_request("GET", "/_slm/stats", params=params)
+        return self.transport.perform_request(
+            "GET", "/_slm/stats", params=params, headers=headers
+        )
 
     @query_params()
-    def put_lifecycle(self, policy_id, body=None, params=None):
+    def put_lifecycle(self, policy_id, body=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/slm-api-put.html>`_
 
@@ -74,29 +85,39 @@ class SlmClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'policy_id'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_slm", "policy", policy_id), params=params, body=body
+            "PUT",
+            _make_path("_slm", "policy", policy_id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def get_status(self, params=None):
+    def get_status(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/slm-get-status.html>`_
 
         """
-        return self.transport.perform_request("GET", "/_slm/status", params=params)
+        return self.transport.perform_request(
+            "GET", "/_slm/status", params=params, headers=headers
+        )
 
     @query_params()
-    def start(self, params=None):
+    def start(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/slm-start.html>`_
 
         """
-        return self.transport.perform_request("POST", "/_slm/start", params=params)
+        return self.transport.perform_request(
+            "POST", "/_slm/start", params=params, headers=headers
+        )
 
     @query_params()
-    def stop(self, params=None):
+    def stop(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/slm-stop.html>`_
 
         """
-        return self.transport.perform_request("POST", "/_slm/stop", params=params)
+        return self.transport.perform_request(
+            "POST", "/_slm/stop", params=params, headers=headers
+        )
diff --git a/elasticsearch/client/snapshot.py b/elasticsearch/client/snapshot.py
index e7456e96..9fc2a411 100644
--- a/elasticsearch/client/snapshot.py
+++ b/elasticsearch/client/snapshot.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class SnapshotClient(NamespacedClient):
     @query_params("master_timeout", "wait_for_completion")
-    def create(self, repository, snapshot, body=None, params=None):
+    def create(self, repository, snapshot, body=None, params=None, headers=None):
         """
         Creates a snapshot in a repository.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -24,11 +24,12 @@ class SnapshotClient(NamespacedClient):
             "PUT",
             _make_path("_snapshot", repository, snapshot),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("master_timeout")
-    def delete(self, repository, snapshot, params=None):
+    def delete(self, repository, snapshot, params=None, headers=None):
         """
         Deletes a snapshot.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -43,11 +44,14 @@ class SnapshotClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_snapshot", repository, snapshot), params=params
+            "DELETE",
+            _make_path("_snapshot", repository, snapshot),
+            params=params,
+            headers=headers,
         )
 
     @query_params("ignore_unavailable", "master_timeout", "verbose")
-    def get(self, repository, snapshot, params=None):
+    def get(self, repository, snapshot, params=None, headers=None):
         """
         Returns information about a snapshot.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -67,11 +71,14 @@ class SnapshotClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "GET", _make_path("_snapshot", repository, snapshot), params=params
+            "GET",
+            _make_path("_snapshot", repository, snapshot),
+            params=params,
+            headers=headers,
         )
 
     @query_params("master_timeout", "timeout")
-    def delete_repository(self, repository, params=None):
+    def delete_repository(self, repository, params=None, headers=None):
         """
         Deletes a repository.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -85,11 +92,14 @@ class SnapshotClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'repository'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_snapshot", repository), params=params
+            "DELETE",
+            _make_path("_snapshot", repository),
+            params=params,
+            headers=headers,
         )
 
     @query_params("local", "master_timeout")
-    def get_repository(self, repository=None, params=None):
+    def get_repository(self, repository=None, params=None, headers=None):
         """
         Returns information about a repository.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -101,11 +111,11 @@ class SnapshotClient(NamespacedClient):
             to master node
         """
         return self.transport.perform_request(
-            "GET", _make_path("_snapshot", repository), params=params
+            "GET", _make_path("_snapshot", repository), params=params, headers=headers
         )
 
     @query_params("master_timeout", "timeout", "verify")
-    def create_repository(self, repository, body, params=None):
+    def create_repository(self, repository, body, params=None, headers=None):
         """
         Creates a repository.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -122,11 +132,15 @@ class SnapshotClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_snapshot", repository), params=params, body=body
+            "PUT",
+            _make_path("_snapshot", repository),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("master_timeout", "wait_for_completion")
-    def restore(self, repository, snapshot, body=None, params=None):
+    def restore(self, repository, snapshot, body=None, params=None, headers=None):
         """
         Restores a snapshot.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -147,11 +161,12 @@ class SnapshotClient(NamespacedClient):
             "POST",
             _make_path("_snapshot", repository, snapshot, "_restore"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params("ignore_unavailable", "master_timeout")
-    def status(self, repository=None, snapshot=None, params=None):
+    def status(self, repository=None, snapshot=None, params=None, headers=None):
         """
         Returns information about the status of a snapshot.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -168,10 +183,11 @@ class SnapshotClient(NamespacedClient):
             "GET",
             _make_path("_snapshot", repository, snapshot, "_status"),
             params=params,
+            headers=headers,
         )
 
     @query_params("master_timeout", "timeout")
-    def verify_repository(self, repository, params=None):
+    def verify_repository(self, repository, params=None, headers=None):
         """
         Verifies a repository.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -185,11 +201,14 @@ class SnapshotClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'repository'.")
 
         return self.transport.perform_request(
-            "POST", _make_path("_snapshot", repository, "_verify"), params=params
+            "POST",
+            _make_path("_snapshot", repository, "_verify"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("master_timeout", "timeout")
-    def cleanup_repository(self, repository, params=None):
+    def cleanup_repository(self, repository, params=None, headers=None):
         """
         Removes stale data from repository.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/modules-snapshots.html>`_
@@ -203,5 +222,8 @@ class SnapshotClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'repository'.")
 
         return self.transport.perform_request(
-            "POST", _make_path("_snapshot", repository, "_cleanup"), params=params
+            "POST",
+            _make_path("_snapshot", repository, "_cleanup"),
+            params=params,
+            headers=headers,
         )
diff --git a/elasticsearch/client/sql.py b/elasticsearch/client/sql.py
index 06af601c..8211c672 100644
--- a/elasticsearch/client/sql.py
+++ b/elasticsearch/client/sql.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, SKIP_IN_PATH
 
 class SqlClient(NamespacedClient):
     @query_params()
-    def clear_cursor(self, body, params=None):
+    def clear_cursor(self, body, params=None, headers=None):
         """
         `<Clear SQL cursor>`_
 
@@ -14,11 +14,11 @@ class SqlClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "POST", "/_sql/close", params=params, body=body
+            "POST", "/_sql/close", params=params, headers=headers, body=body
         )
 
     @query_params("format")
-    def query(self, body, params=None):
+    def query(self, body, params=None, headers=None):
         """
         `<Execute SQL>`_
 
@@ -30,10 +30,12 @@ class SqlClient(NamespacedClient):
         if body in SKIP_IN_PATH:
             raise ValueError("Empty value passed for a required argument 'body'.")
 
-        return self.transport.perform_request("POST", "/_sql", params=params, body=body)
+        return self.transport.perform_request(
+            "POST", "/_sql", params=params, headers=headers, body=body
+        )
 
     @query_params()
-    def translate(self, body, params=None):
+    def translate(self, body, params=None, headers=None):
         """
         `<Translate SQL into Elasticsearch queries>`_
 
@@ -43,5 +45,5 @@ class SqlClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "POST", "/_sql/translate", params=params, body=body
+            "POST", "/_sql/translate", params=params, headers=headers, body=body
         )
diff --git a/elasticsearch/client/ssl.py b/elasticsearch/client/ssl.py
index 5428ca03..66ec2855 100644
--- a/elasticsearch/client/ssl.py
+++ b/elasticsearch/client/ssl.py
@@ -3,11 +3,11 @@ from .utils import NamespacedClient, query_params
 
 class SslClient(NamespacedClient):
     @query_params()
-    def certificates(self, params=None):
+    def certificates(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-ssl.html>`_
 
         """
         return self.transport.perform_request(
-            "GET", "/_ssl/certificates", params=params
+            "GET", "/_ssl/certificates", params=params, headers=headers
         )
diff --git a/elasticsearch/client/tasks.py b/elasticsearch/client/tasks.py
index 1593cf8e..0f253ca1 100644
--- a/elasticsearch/client/tasks.py
+++ b/elasticsearch/client/tasks.py
@@ -11,7 +11,7 @@ class TasksClient(NamespacedClient):
         "timeout",
         "wait_for_completion",
     )
-    def list(self, params=None):
+    def list(self, params=None, headers=None):
         """
         Returns a list of tasks.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/tasks.html>`_
@@ -30,10 +30,12 @@ class TasksClient(NamespacedClient):
         :arg wait_for_completion: Wait for the matching tasks to
             complete (default: false)
         """
-        return self.transport.perform_request("GET", "/_tasks", params=params)
+        return self.transport.perform_request(
+            "GET", "/_tasks", params=params, headers=headers
+        )
 
     @query_params("actions", "nodes", "parent_task_id")
-    def cancel(self, task_id=None, params=None):
+    def cancel(self, task_id=None, params=None, headers=None):
         """
         Cancels a task, if it can be cancelled through an API.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/tasks.html>`_
@@ -49,11 +51,14 @@ class TasksClient(NamespacedClient):
             (node_id:task_number). Set to -1 to cancel all.
         """
         return self.transport.perform_request(
-            "POST", _make_path("_tasks", task_id, "_cancel"), params=params
+            "POST",
+            _make_path("_tasks", task_id, "_cancel"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("timeout", "wait_for_completion")
-    def get(self, task_id, params=None):
+    def get(self, task_id, params=None, headers=None):
         """
         Returns information about a task.
         `<https://www.elastic.co/guide/en/elasticsearch/reference/master/tasks.html>`_
@@ -68,5 +73,5 @@ class TasksClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'task_id'.")
 
         return self.transport.perform_request(
-            "GET", _make_path("_tasks", task_id), params=params
+            "GET", _make_path("_tasks", task_id), params=params, headers=headers
         )
diff --git a/elasticsearch/client/transform.py b/elasticsearch/client/transform.py
index b4345713..0d9aadcf 100644
--- a/elasticsearch/client/transform.py
+++ b/elasticsearch/client/transform.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class TransformClient(NamespacedClient):
     @query_params("force")
-    def delete_transform(self, transform_id, params=None):
+    def delete_transform(self, transform_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/delete-transform.html>`_
 
@@ -18,11 +18,14 @@ class TransformClient(NamespacedClient):
             )
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_transform", transform_id), params=params
+            "DELETE",
+            _make_path("_transform", transform_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params("allow_no_match", "from_", "size")
-    def get_transform(self, transform_id=None, params=None):
+    def get_transform(self, transform_id=None, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/get-transform.html>`_
 
@@ -41,11 +44,14 @@ class TransformClient(NamespacedClient):
             params["from"] = params.pop("from_")
 
         return self.transport.perform_request(
-            "GET", _make_path("_transform", transform_id), params=params
+            "GET",
+            _make_path("_transform", transform_id),
+            params=params,
+            headers=headers,
         )
 
     @query_params("allow_no_match", "from_", "size")
-    def get_transform_stats(self, transform_id, params=None):
+    def get_transform_stats(self, transform_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/get-transform-stats.html>`_
 
@@ -68,11 +74,14 @@ class TransformClient(NamespacedClient):
             )
 
         return self.transport.perform_request(
-            "GET", _make_path("_transform", transform_id, "_stats"), params=params
+            "GET",
+            _make_path("_transform", transform_id, "_stats"),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def preview_transform(self, body, params=None):
+    def preview_transform(self, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/preview-transform.html>`_
 
@@ -82,11 +91,11 @@ class TransformClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'body'.")
 
         return self.transport.perform_request(
-            "POST", "/_transform/_preview", params=params, body=body
+            "POST", "/_transform/_preview", params=params, headers=headers, body=body
         )
 
     @query_params("defer_validation")
-    def put_transform(self, transform_id, body, params=None):
+    def put_transform(self, transform_id, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/put-transform.html>`_
 
@@ -100,11 +109,15 @@ class TransformClient(NamespacedClient):
                 raise ValueError("Empty value passed for a required argument.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_transform", transform_id), params=params, body=body
+            "PUT",
+            _make_path("_transform", transform_id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params("timeout")
-    def start_transform(self, transform_id, params=None):
+    def start_transform(self, transform_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/start-transform.html>`_
 
@@ -118,11 +131,14 @@ class TransformClient(NamespacedClient):
             )
 
         return self.transport.perform_request(
-            "POST", _make_path("_transform", transform_id, "_start"), params=params
+            "POST",
+            _make_path("_transform", transform_id, "_start"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("allow_no_match", "timeout", "wait_for_completion")
-    def stop_transform(self, transform_id, params=None):
+    def stop_transform(self, transform_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/stop-transform.html>`_
 
@@ -141,11 +157,14 @@ class TransformClient(NamespacedClient):
             )
 
         return self.transport.perform_request(
-            "POST", _make_path("_transform", transform_id, "_stop"), params=params
+            "POST",
+            _make_path("_transform", transform_id, "_stop"),
+            params=params,
+            headers=headers,
         )
 
     @query_params("defer_validation")
-    def update_transform(self, transform_id, body, params=None):
+    def update_transform(self, transform_id, body, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/update-transform.html>`_
 
@@ -162,5 +181,6 @@ class TransformClient(NamespacedClient):
             "POST",
             _make_path("_transform", transform_id, "_update"),
             params=params,
+            headers=headers,
             body=body,
         )
diff --git a/elasticsearch/client/utils.py b/elasticsearch/client/utils.py
index 8cd22159..3baa7666 100644
--- a/elasticsearch/client/utils.py
+++ b/elasticsearch/client/utils.py
@@ -69,19 +69,27 @@ def query_params(*es_query_params):
         @wraps(func)
         def _wrapped(*args, **kwargs):
             params = {}
+            headers = {}
             if "params" in kwargs:
                 params = kwargs.pop("params").copy()
+            if "headers" in kwargs:
+                headers = {
+                    k.lower(): v for k, v in (kwargs.pop("headers") or {}).items()
+                }
+            if "opaque_id" in kwargs:
+                headers["x-opaque-id"] = kwargs.pop("opaque_id")
+
             for p in es_query_params + GLOBAL_PARAMS:
                 if p in kwargs:
                     v = kwargs.pop(p)
                     if v is not None:
                         params[p] = _escape(v)
 
-            # don't treat ignore and request_timeout as other params to avoid escaping
+            # don't treat ignore, request_timeout, and opaque_id as other params to avoid escaping
             for p in ("ignore", "request_timeout"):
                 if p in kwargs:
                     params[p] = kwargs.pop(p)
-            return func(*args, params=params, **kwargs)
+            return func(*args, params=params, headers=headers, **kwargs)
 
         return _wrapped
 
diff --git a/elasticsearch/client/watcher.py b/elasticsearch/client/watcher.py
index e4fb5efd..5cc707cb 100644
--- a/elasticsearch/client/watcher.py
+++ b/elasticsearch/client/watcher.py
@@ -3,7 +3,7 @@ from .utils import NamespacedClient, query_params, _make_path, SKIP_IN_PATH
 
 class WatcherClient(NamespacedClient):
     @query_params()
-    def ack_watch(self, watch_id, action_id=None, params=None):
+    def ack_watch(self, watch_id, action_id=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-ack-watch.html>`_
 
@@ -18,10 +18,11 @@ class WatcherClient(NamespacedClient):
             "PUT",
             _make_path("_watcher", "watch", watch_id, "_ack", action_id),
             params=params,
+            headers=headers,
         )
 
     @query_params()
-    def activate_watch(self, watch_id, params=None):
+    def activate_watch(self, watch_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-activate-watch.html>`_
 
@@ -31,11 +32,14 @@ class WatcherClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'watch_id'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_watcher", "watch", watch_id, "_activate"), params=params
+            "PUT",
+            _make_path("_watcher", "watch", watch_id, "_activate"),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def deactivate_watch(self, watch_id, params=None):
+    def deactivate_watch(self, watch_id, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-deactivate-watch.html>`_
 
@@ -48,10 +52,11 @@ class WatcherClient(NamespacedClient):
             "PUT",
             _make_path("_watcher", "watch", watch_id, "_deactivate"),
             params=params,
+            headers=headers,
         )
 
     @query_params()
-    def delete_watch(self, id, params=None):
+    def delete_watch(self, id, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-delete-watch.html>`_
 
@@ -61,11 +66,14 @@ class WatcherClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "DELETE", _make_path("_watcher", "watch", id), params=params
+            "DELETE",
+            _make_path("_watcher", "watch", id),
+            params=params,
+            headers=headers,
         )
 
     @query_params("debug")
-    def execute_watch(self, body=None, id=None, params=None):
+    def execute_watch(self, body=None, id=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-execute-watch.html>`_
 
@@ -78,11 +86,12 @@ class WatcherClient(NamespacedClient):
             "PUT",
             _make_path("_watcher", "watch", id, "_execute"),
             params=params,
+            headers=headers,
             body=body,
         )
 
     @query_params()
-    def get_watch(self, id, params=None):
+    def get_watch(self, id, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-get-watch.html>`_
 
@@ -92,11 +101,11 @@ class WatcherClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "GET", _make_path("_watcher", "watch", id), params=params
+            "GET", _make_path("_watcher", "watch", id), params=params, headers=headers
         )
 
     @query_params("active", "if_primary_term", "if_seq_no", "version")
-    def put_watch(self, id, body=None, params=None):
+    def put_watch(self, id, body=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-put-watch.html>`_
 
@@ -113,19 +122,25 @@ class WatcherClient(NamespacedClient):
             raise ValueError("Empty value passed for a required argument 'id'.")
 
         return self.transport.perform_request(
-            "PUT", _make_path("_watcher", "watch", id), params=params, body=body
+            "PUT",
+            _make_path("_watcher", "watch", id),
+            params=params,
+            headers=headers,
+            body=body,
         )
 
     @query_params()
-    def start(self, params=None):
+    def start(self, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-start.html>`_
 
         """
-        return self.transport.perform_request("POST", "/_watcher/_start", params=params)
+        return self.transport.perform_request(
+            "POST", "/_watcher/_start", params=params, headers=headers
+        )
 
     @query_params("emit_stacktraces")
-    def stats(self, metric=None, params=None):
+    def stats(self, metric=None, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-stats.html>`_
 
@@ -139,13 +154,18 @@ class WatcherClient(NamespacedClient):
             current_watches, pending_watches
         """
         return self.transport.perform_request(
-            "GET", _make_path("_watcher", "stats", metric), params=params
+            "GET",
+            _make_path("_watcher", "stats", metric),
+            params=params,
+            headers=headers,
         )
 
     @query_params()
-    def stop(self, params=None):
+    def stop(self, params=None, headers=None):
         """
         `<http://www.elastic.co/guide/en/elasticsearch/reference/current/watcher-api-stop.html>`_
 
         """
-        return self.transport.perform_request("POST", "/_watcher/_stop", params=params)
+        return self.transport.perform_request(
+            "POST", "/_watcher/_stop", params=params, headers=headers
+        )
diff --git a/elasticsearch/client/xpack.py b/elasticsearch/client/xpack.py
index 489fc7b0..de0aa80f 100644
--- a/elasticsearch/client/xpack.py
+++ b/elasticsearch/client/xpack.py
@@ -7,20 +7,24 @@ class XPackClient(NamespacedClient):
 
     # AUTO-GENERATED-API-DEFINITIONS #
     @query_params("categories")
-    def info(self, params=None):
+    def info(self, params=None, headers=None):
         """
         `<https://www.elastic.co/guide/en/elasticsearch/reference/current/info-api.html>`_
 
         :arg categories: Comma-separated list of info categories. Can be
             any of: build, license, features
         """
-        return self.transport.perform_request("GET", "/_xpack", params=params)
+        return self.transport.perform_request(
+            "GET", "/_xpack", params=params, headers=headers
+        )
 
     @query_params("master_timeout")
-    def usage(self, params=None):
+    def usage(self, params=None, headers=None):
         """
         `<Retrieve information about xpack features usage>`_
 
         :arg master_timeout: Specify timeout for watch write operation
         """
-        return self.transport.perform_request("GET", "/_xpack/usage", params=params)
+        return self.transport.perform_request(
+            "GET", "/_xpack/usage", params=params, headers=headers
+        )
diff --git a/elasticsearch/connection/base.py b/elasticsearch/connection/base.py
index 37386bec..9b2344e4 100644
--- a/elasticsearch/connection/base.py
+++ b/elasticsearch/connection/base.py
@@ -37,6 +37,8 @@ class Connection(object):
     :arg timeout: default timeout in seconds (float, default: 10)
     :arg http_compress: Use gzip compression
     :arg cloud_id: The Cloud ID from ElasticCloud. Convenient way to connect to cloud instances.
+    :arg opaque_id: Send this value in the 'X-Opaque-Id' HTTP header
+        For tracing all requests made by this transport.
     """
 
     def __init__(
@@ -50,6 +52,7 @@ class Connection(object):
         http_compress=None,
         cloud_id=None,
         api_key=None,
+        opaque_id=None,
         **kwargs
     ):
 
@@ -78,6 +81,8 @@ class Connection(object):
         headers = headers or {}
         for key in headers:
             self.headers[key.lower()] = headers[key]
+        if opaque_id:
+            self.headers["x-opaque-id"] = opaque_id
 
         self.headers.setdefault("content-type", "application/json")
         self.headers.setdefault("user-agent", self._get_default_user_agent())
diff --git a/elasticsearch/connection/http_requests.py b/elasticsearch/connection/http_requests.py
index 733f694c..9612f13e 100644
--- a/elasticsearch/connection/http_requests.py
+++ b/elasticsearch/connection/http_requests.py
@@ -38,6 +38,8 @@ class RequestsHttpConnection(Connection):
     :arg cloud_id: The Cloud ID from ElasticCloud. Convenient way to connect to cloud instances.
         Other host connection params will be ignored.
     :arg api_key: optional API Key authentication as either base64 encoded string or a tuple.
+    :arg opaque_id: Send this value in the 'X-Opaque-Id' HTTP header
+        For tracing all requests made by this transport.
     """
 
     def __init__(
@@ -55,6 +57,7 @@ class RequestsHttpConnection(Connection):
         http_compress=None,
         cloud_id=None,
         api_key=None,
+        opaque_id=None,
         **kwargs
     ):
         if not REQUESTS_AVAILABLE:
@@ -75,6 +78,7 @@ class RequestsHttpConnection(Connection):
             http_compress=http_compress,
             cloud_id=cloud_id,
             api_key=api_key,
+            opaque_id=opaque_id,
             **kwargs
         )
 
diff --git a/elasticsearch/connection/http_urllib3.py b/elasticsearch/connection/http_urllib3.py
index 8273df33..81223926 100644
--- a/elasticsearch/connection/http_urllib3.py
+++ b/elasticsearch/connection/http_urllib3.py
@@ -75,6 +75,8 @@ class Urllib3HttpConnection(Connection):
     :arg cloud_id: The Cloud ID from ElasticCloud. Convenient way to connect to cloud instances.
         Other host connection params will be ignored.
     :arg api_key: optional API Key authentication as either base64 encoded string or a tuple.
+    :arg opaque_id: Send this value in the 'X-Opaque-Id' HTTP header
+        For tracing all requests made by this transport.
     """
 
     def __init__(
@@ -97,6 +99,7 @@ class Urllib3HttpConnection(Connection):
         http_compress=None,
         cloud_id=None,
         api_key=None,
+        opaque_id=None,
         **kwargs
     ):
         # Initialize headers before calling super().__init__().
@@ -110,6 +113,7 @@ class Urllib3HttpConnection(Connection):
             http_compress=http_compress,
             cloud_id=cloud_id,
             api_key=api_key,
+            opaque_id=opaque_id,
             **kwargs
         )
         if http_auth is not None:
diff --git a/elasticsearch/transport.py b/elasticsearch/transport.py
index 2a2bde98..ccf599db 100644
--- a/elasticsearch/transport.py
+++ b/elasticsearch/transport.py
@@ -342,6 +342,7 @@ class Transport(object):
             ignore = params.pop("ignore", ())
             if isinstance(ignore, int):
                 ignore = (ignore,)
+
         for attempt in range(self.max_retries + 1):
             connection = self.get_connection()
 
diff --git a/test_elasticsearch/test_cases.py b/test_elasticsearch/test_cases.py
index 7f71f358..72b5dc87 100644
--- a/test_elasticsearch/test_cases.py
+++ b/test_elasticsearch/test_cases.py
@@ -11,12 +11,12 @@ class DummyTransport(object):
         self.call_count = 0
         self.calls = defaultdict(list)
 
-    def perform_request(self, method, url, params=None, body=None):
+    def perform_request(self, method, url, params=None, headers=None, body=None):
         resp = 200, {}
         if self.responses:
             resp = self.responses[self.call_count]
         self.call_count += 1
-        self.calls[(method, url)].append((params, body))
+        self.calls[(method, url)].append((params, headers, body))
         return resp
 
 
@@ -46,4 +46,6 @@ class TestElasticsearchTestCase(ElasticsearchTestCase):
         self.client.transport.perform_request("GET", "/")
         self.client.transport.perform_request("DELETE", "/42", params={}, body="body")
         self.assert_call_count_equals(2)
-        self.assertEquals([({}, "body")], self.assert_url_called("DELETE", "/42", 1))
+        self.assertEquals(
+            [({}, None, "body")], self.assert_url_called("DELETE", "/42", 1)
+        )
diff --git a/test_elasticsearch/test_client/__init__.py b/test_elasticsearch/test_client/__init__.py
index 8e0c67ca..a43e9427 100644
--- a/test_elasticsearch/test_client/__init__.py
+++ b/test_elasticsearch/test_client/__init__.py
@@ -52,7 +52,7 @@ class TestClient(ElasticsearchTestCase):
     def test_request_timeout_is_passed_through_unescaped(self):
         self.client.ping(request_timeout=0.1)
         calls = self.assert_url_called("HEAD", "/")
-        self.assertEquals([({"request_timeout": 0.1}, None)], calls)
+        self.assertEquals([({"request_timeout": 0.1}, {}, None)], calls)
 
     def test_params_is_copied_when(self):
         rt = object()
@@ -61,14 +61,27 @@ class TestClient(ElasticsearchTestCase):
         self.client.ping(params=params)
         calls = self.assert_url_called("HEAD", "/", 2)
         self.assertEquals(
-            [({"request_timeout": rt}, None), ({"request_timeout": rt}, None)], calls
+            [({"request_timeout": rt}, {}, None), ({"request_timeout": rt}, {}, None)],
+            calls,
+        )
+        self.assertFalse(calls[0][0] is calls[1][0])
+
+    def test_headers_is_copied_when(self):
+        hv = "value"
+        headers = dict(Authentication=hv)
+        self.client.ping(headers=headers)
+        self.client.ping(headers=headers)
+        calls = self.assert_url_called("HEAD", "/", 2)
+        self.assertEquals(
+            [({}, {"authentication": hv}, None), ({}, {"authentication": hv}, None)],
+            calls,
         )
         self.assertFalse(calls[0][0] is calls[1][0])
 
     def test_from_in_search(self):
         self.client.search(index="i", from_=10)
         calls = self.assert_url_called("GET", "/i/_search")
-        self.assertEquals([({"from": "10"}, None)], calls)
+        self.assertEquals([({"from": "10"}, {}, None)], calls)
 
     def test_repr_contains_hosts(self):
         self.assertEquals("<Elasticsearch([{}])>", repr(self.client))
diff --git a/test_elasticsearch/test_client/test_utils.py b/test_elasticsearch/test_client/test_utils.py
index e30d8b14..4a510eea 100644
--- a/test_elasticsearch/test_client/test_utils.py
+++ b/test_elasticsearch/test_client/test_utils.py
@@ -1,12 +1,48 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
-from elasticsearch.client.utils import _make_path, _escape
+from elasticsearch.client.utils import _make_path, _escape, query_params
 from elasticsearch.compat import PY2
 
 from ..test_cases import TestCase, SkipTest
 
 
+class TestQueryParams(TestCase):
+    def setUp(self):
+        self.calls = []
+
+    @query_params("simple_param")
+    def func_to_wrap(self, *args, **kwargs):
+        self.calls.append((args, kwargs))
+
+    def test_handles_params(self):
+        self.func_to_wrap(params={"simple_param_2": "2"}, simple_param="3")
+        self.assertEqual(
+            self.calls,
+            [
+                (
+                    (),
+                    {
+                        "params": {"simple_param": b"3", "simple_param_2": "2"},
+                        "headers": {},
+                    },
+                )
+            ],
+        )
+
+    def test_handles_headers(self):
+        self.func_to_wrap(headers={"X-Opaque-Id": "app-1"})
+        self.assertEqual(
+            self.calls, [((), {"params": {}, "headers": {"x-opaque-id": "app-1"}})]
+        )
+
+    def test_handles_opaque_id(self):
+        self.func_to_wrap(opaque_id="request-id")
+        self.assertEqual(
+            self.calls, [((), {"params": {}, "headers": {"x-opaque-id": "request-id"}})]
+        )
+
+
 class TestMakePath(TestCase):
     def test_handles_unicode(self):
         id = "中文"
diff --git a/test_elasticsearch/test_connection.py b/test_elasticsearch/test_connection.py
index e4aa8e13..436a142a 100644
--- a/test_elasticsearch/test_connection.py
+++ b/test_elasticsearch/test_connection.py
@@ -55,6 +55,10 @@ class TestUrllib3Connection(TestCase):
         self.assertIsInstance(con.pool.conn_kw["ssl_context"], ssl.SSLContext)
         self.assertTrue(con.use_ssl)
 
+    def test_opaque_id(self):
+        con = Urllib3HttpConnection(opaque_id="app-1")
+        self.assertEqual(con.headers["x-opaque-id"], "app-1")
+
     def test_http_cloud_id(self):
         con = Urllib3HttpConnection(
             cloud_id="foobar:ZXhhbXBsZS5jbG91ZC5jb20kMGZkNTBmNjIzMjBlZDY1MzlmNmNiNDhlMWI2OCRhYzUzOTVhODgz\nNDU2NmM5ZjE1Y2Q4ZTQ5MGE=\n"
@@ -317,6 +321,10 @@ class TestRequestsConnection(TestCase):
         con = RequestsHttpConnection(timeout=42)
         self.assertEquals(42, con.timeout)
 
+    def test_opaque_id(self):
+        con = RequestsHttpConnection(opaque_id="app-1")
+        self.assertEqual(con.headers["x-opaque-id"], "app-1")
+
     def test_http_cloud_id(self):
         con = RequestsHttpConnection(
             cloud_id="foobar:ZXhhbXBsZS5jbG91ZC5jb20kMGZkNTBmNjIzMjBlZDY1MzlmNmNiNDhlMWI2OCRhYzUzOTVhODgz\nNDU2NmM5ZjE1Y2Q4ZTQ5MGE=\n"
diff --git a/test_elasticsearch/test_server/test_common.py b/test_elasticsearch/test_server/test_common.py
index 5b83ab40..9d159336 100644
--- a/test_elasticsearch/test_server/test_common.py
+++ b/test_elasticsearch/test_server/test_common.py
@@ -164,13 +164,12 @@ class YamlTestCase(ElasticsearchTestCase):
     def run_do(self, action):
         """ Perform an api call with given parameters. """
         api = self.client
-        if "headers" in action:
-            api = self._get_client(headers=action.pop("headers"))
-
+        headers = action.pop("headers", None)
         catch = action.pop("catch", None)
         self.assertEquals(1, len(action))
 
         method, args = list(action.items())[0]
+        args["headers"] = headers
 
         # locate api endpoint
         for m in method.split("."):
diff --git a/test_elasticsearch/test_transport.py b/test_elasticsearch/test_transport.py
index a0b87298..443db719 100644
--- a/test_elasticsearch/test_transport.py
+++ b/test_elasticsearch/test_transport.py
@@ -111,6 +111,26 @@ class TestTransport(TestCase):
             t.get_connection().calls[0][1],
         )
 
+    def test_opaque_id(self):
+        t = Transport([{}], opaque_id="app-1", connection_class=DummyConnection)
+
+        t.perform_request("GET", "/")
+        self.assertEquals(1, len(t.get_connection().calls))
+        self.assertEquals(("GET", "/", None, None), t.get_connection().calls[0][0])
+        self.assertEquals(
+            {"timeout": None, "ignore": (), "headers": None},
+            t.get_connection().calls[0][1],
+        )
+
+        # Now try with an 'x-opaque-id' set on perform_request().
+        t.perform_request("GET", "/", headers={"x-opaque-id": "request-1"})
+        self.assertEquals(2, len(t.get_connection().calls))
+        self.assertEquals(("GET", "/", None, None), t.get_connection().calls[1][0])
+        self.assertEquals(
+            {"timeout": None, "ignore": (), "headers": {"x-opaque-id": "request-1"}},
+            t.get_connection().calls[1][1],
+        )
+
     def test_request_with_custom_user_agent_header(self):
         t = Transport([{}], connection_class=DummyConnection)
 
diff --git a/utils/templates/base b/utils/templates/base
index b4f69880..27aa8dde 100644
--- a/utils/templates/base
+++ b/utils/templates/base
@@ -24,6 +24,6 @@
         body = _bulk_body(self.transport.serializer, body)
         {% endif %}
         {% block request %}
-        return self.transport.perform_request("{{ api.method }}", {% include "url" %}, params=params{% if api.body %}, body=body{% endif %})
+        return self.transport.perform_request("{{ api.method }}", {% include "url" %}, params=params, headers=headers{% if api.body %}, body=body{% endif %})
         {% endblock %}
 
diff --git a/utils/templates/func_params b/utils/templates/func_params
index 42dec2b2..067e8f12 100644
--- a/utils/templates/func_params
+++ b/utils/templates/func_params
@@ -10,4 +10,5 @@
   {% if not info.required %}{{ p }}=None, {% endif %}
 {% endfor %}
 
-params=None
+params=None,
+headers=None
diff --git a/utils/templates/overrides/__init__/clear_scroll b/utils/templates/overrides/__init__/clear_scroll
index dde2170e..1176551f 100644
--- a/utils/templates/overrides/__init__/clear_scroll
+++ b/utils/templates/overrides/__init__/clear_scroll
@@ -7,6 +7,6 @@
         elif scroll_id:
             params["scroll_id"] = scroll_id
 
-        return self.transport.perform_request("{{ api.method }}", "/_search/scroll", params=params, body=body)
+        return self.transport.perform_request("{{ api.method }}", "/_search/scroll", params=params, headers=headers, body=body)
 {% endblock %}
 
diff --git a/utils/templates/overrides/__init__/index b/utils/templates/overrides/__init__/index
index 9aae46a7..37fbc41b 100644
--- a/utils/templates/overrides/__init__/index
+++ b/utils/templates/overrides/__init__/index
@@ -4,6 +4,6 @@
             doc_type = "_doc"
 
 
-        return self.transport.perform_request("POST" if id in SKIP_IN_PATH else "PUT", {% include "url" %}, params=params, body=body)
+        return self.transport.perform_request("POST" if id in SKIP_IN_PATH else "PUT", {% include "url" %}, params=params, headers=headers, body=body)
 {% endblock %}
 
diff --git a/utils/templates/overrides/__init__/scroll b/utils/templates/overrides/__init__/scroll
index 6ea4fbff..5a6ae833 100644
--- a/utils/templates/overrides/__init__/scroll
+++ b/utils/templates/overrides/__init__/scroll
@@ -7,6 +7,6 @@
         elif scroll_id:
             params["scroll_id"] = scroll_id
 
-        return self.transport.perform_request("{{ api.method }}", "/_search/scroll", params=params, body=body)
+        return self.transport.perform_request("{{ api.method }}", "/_search/scroll", params=params, headers=headers, body=body)
 {% endblock %}
 
diff --git a/utils/templates/overrides/cluster/stats b/utils/templates/overrides/cluster/stats
index c5bd1c64..aed2d3b1 100644
--- a/utils/templates/overrides/cluster/stats
+++ b/utils/templates/overrides/cluster/stats
@@ -1,5 +1,5 @@
 {% extends "base" %}
 {% block request %}
-        return self.transport.perform_request("{{ api.method }}", "/_cluster/stats" if node_id in SKIP_IN_PATH else _make_path("_cluster", "stats", "nodes", node_id), params=params)
+        return self.transport.perform_request("{{ api.method }}", "/_cluster/stats" if node_id in SKIP_IN_PATH else _make_path("_cluster", "stats", "nodes", node_id), params=params, headers=headers)
 {% endblock%}