attempt deduplicating x-goog-api-client headers

Author: daniel-sanche

packages/google-api-core/google/api_core/gapic_v1/method.py

@@ -114,14 +114,25 @@ def __call__(
 
         # Add the user agent metadata to the call.
         if self._metadata is not None:
-            metadata = kwargs.get("metadata", [])
-            # Due to the nature of invocation, None should be treated the same
-            # as not specified.
-            if metadata is None:
-                metadata = []
-            metadata = list(metadata)
-            metadata.extend(self._metadata)
-            kwargs["metadata"] = metadata
+            metadata = kwargs.get("metadata")
+            if not metadata:
+                kwargs["metadata"] = self._metadata
+            else:
+                # Merge user-supplied metadata with library-supplied metadata.
+                # All keys in gRPC metadata are already lowercase.
+                from itertools import chain
+                metadata = list(metadata)
+                api_client_values = []
+                merged_metadata = []
+                for key, val in chain(metadata, self._metadata):
+                    if key == "x-goog-api-client":
+                        api_client_values.append(val)
+                    else:
+                        merged_metadata.append((key, val))
+                if api_client_values:
+                    merged_metadata.append(("x-goog-api-client", " ".join(api_client_values)))
+                kwargs["metadata"] = merged_metadata
+
         if self._compression is not None:
             kwargs["compression"] = compression
 

packages/google-api-core/google/api_core/grpc_helpers.py

@@ -254,11 +254,20 @@ def _create_composite_credentials(
     request = google.auth.transport.requests.Request()
 
     # Create the metadata plugin for inserting the authorization header.
-    metadata_plugin = google.auth.transport.grpc.AuthMetadataPlugin(
-        credentials,
-        request,
-        default_host=default_host,
-    )
+    try:
+        metadata_plugin = google.auth.transport.grpc.AuthMetadataPlugin(
+            credentials,
+            request,
+            default_host=default_host,
+            suppress_metrics_header=True,
+        )
+    except TypeError:
+        # Support older versions of google-auth that do not accept suppress_metrics_header
+        metadata_plugin = google.auth.transport.grpc.AuthMetadataPlugin(
+            credentials,
+            request,
+            default_host=default_host,
+        )
 
     # Create a set of grpc.CallCredentials using the metadata plugin.
     google_auth_credentials = grpc.metadata_call_credentials(metadata_plugin)

packages/google-auth/google/auth/transport/grpc.py

@@ -49,14 +49,15 @@ class AuthMetadataPlugin(grpc.AuthMetadataPlugin):
             account credentials.
     """
 
-    def __init__(self, credentials, request, default_host=None):
+    def __init__(self, credentials, request, default_host=None, suppress_metrics_header=False):
         # pylint: disable=no-value-for-parameter
         # pylint doesn't realize that the super method takes no arguments
         # because this class is the same name as the superclass.
         super(AuthMetadataPlugin, self).__init__()
         self._credentials = credentials
         self._request = request
         self._default_host = default_host
+        self._suppress_metrics_header = suppress_metrics_header
 
     def _get_authorization_headers(self, context):
         """Gets the authorization headers for a request.
@@ -80,6 +81,9 @@ def _get_authorization_headers(self, context):
             self._request, context.method_name, context.service_url, headers
         )
 
+        if self._suppress_metrics_header and "x-goog-api-client" in headers:
+            del headers["x-goog-api-client"]
+
         return list(headers.items())
 
     def __call__(self, context, callback):

packages/google-auth/tests/transport/test_grpc.py

@@ -132,6 +132,33 @@ def test__get_authorization_headers_with_service_account_and_default_host(self):
             "https://{}/".format(default_host)
         )
 
+    def test_suppress_metrics_header(self):
+        credentials = mock.create_autospec(service_account.Credentials)
+        # Mock credentials before_request that adds metric and authorization
+        def mock_before_request(request, method, url, headers):
+            headers["x-goog-api-client"] = "foo"
+            headers["authorization"] = "Bearer token"
+        credentials.before_request.side_effect = mock_before_request
+        request = mock.create_autospec(transport.Request)
+
+        # By default, suppress_metrics_header=False
+        plugin = google.auth.transport.grpc.AuthMetadataPlugin(credentials, request)
+        context = mock.create_autospec(grpc.AuthMetadataContext, instance=True)
+        context.method_name = "methodName"
+        context.service_url = "https://pubsub.googleapis.com/methodName"
+
+        headers = dict(plugin._get_authorization_headers(context))
+        assert "x-goog-api-client" in headers
+        assert headers["x-goog-api-client"] == "foo"
+
+        # With suppress_metrics_header=True
+        plugin_suppressed = google.auth.transport.grpc.AuthMetadataPlugin(
+            credentials, request, suppress_metrics_header=True
+        )
+        headers_suppressed = dict(plugin_suppressed._get_authorization_headers(context))
+        assert "x-goog-api-client" not in headers_suppressed
+        assert headers_suppressed["authorization"] == "Bearer token"
+
 
 @mock.patch(
     "google.auth.transport._mtls_helper.get_client_ssl_credentials", autospec=True