[feat] Retries. (#103)

This commit adds automatic retries for both idempotent and
non-idempotent requests.

gapic/schema/wrappers.py

@@ -436,6 +436,16 @@ def grpc_stub_type(self) -> str:
             server='stream' if self.server_streaming else 'unary',
         )
 
+    @utils.cached_property
+    def idempotent(self) -> bool:
+        """Return True if we know this method is idempotent, False otherwise.
+
+        Note: We are intentionally conservative here. It is far less bad
+        to falsely believe an idempotent method is non-idempotent than
+        the converse.
+        """
+        return bool(self.options.Extensions[annotations_pb2.http].get)
+
     @utils.cached_property
     def ref_types(self) -> Sequence[Union[MessageType, EnumType]]:
         """Return types referenced by this method."""

gapic/templates/$namespace/$name_$version/$sub/services/$service/client.py.j2

@@ -4,8 +4,9 @@
 import pkg_resources
 from typing import Mapping, Optional, Sequence, Tuple, Type, Union
 
+from google.api_core import exceptions
 from google.api_core import gapic_v1
-from google.api_core import retry
+from google.api_core import retry as retries
 from google.auth import credentials
 
 {% for import_ in service.python_modules -%}
@@ -54,7 +55,7 @@ class {{ service.name }}:
             {% for field in method.flattened_fields.values() -%}
             {{ field.name }}: {{ field.ident }} = None,
             {% endfor -%}
-            retry: retry.Retry = None,
+            retry: retries.Retry = gapic_v1.method.DEFAULT,
             timeout: float = None,
             metadata: Sequence[Tuple[str, str]] = (),
             ) -> {{ method.output.ident }}:
@@ -71,7 +72,7 @@ class {{ service.name }}:
                 on the ``request`` instance; if ``request`` is provided, this
                 should not be set.
             {% endfor -%}
-            retry (~.retry.Retry): Designation of what errors, if any,
+            retry (~.retries.Retry): Designation of what errors, if any,
                 should be retried.
             timeout (float): The timeout for this request.
             metadata (Sequence[Tuple[str, str]]): Strings which should be
@@ -106,8 +107,16 @@ class {{ service.name }}:
         # and friendly error handling.
         rpc = gapic_v1.method.wrap_method(
             self._transport.{{ method.name|snake_case }},
-            default_retry=None,  # FIXME
-            default_timeout=None,  # FIXME
+            default_retry=retries.Retry(predicate=retries.if_exception_type(
+                {%- if method.idempotent %}
+                exceptions.Aborted,
+                {%- endif %}
+                exceptions.ServiceUnavailable,
+                {%- if method.idempotent %}
+                exceptions.Unknown,
+                {%- endif %}
+            )),
+            default_timeout=None,
             client_info=_client_info,
         )
         {%- if method.field_headers %}

tests/system/test_retry.py

@@ -0,0 +1,69 @@
+# Copyright 2019 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import time
+from unittest import mock
+
+import pytest
+
+from google import showcase_v1alpha3
+from google.api_core import exceptions
+from google.rpc import code_pb2
+
+
+def test_retry_nonidempotent(echo):
+    # Define our error and OK responses.
+    err = exceptions.ServiceUnavailable(message='whups')
+    ok = showcase_v1alpha3.EchoResponse(content='foo')
+    server = mock.Mock(side_effect=(err, err, ok))
+
+    # Mock the transport to send back the error responses followed by a
+    # success response.
+    transport = type(echo).get_transport_class()
+    with mock.patch.object(transport, 'echo',
+            new_callable=mock.PropertyMock(return_value=server)):
+        with mock.patch.object(time, 'sleep'):
+            response = echo.echo({'content': 'bar'})
+        assert response.content == 'foo'
+        assert server.call_count == 3
+
+
+def test_retry_idempotent(identity):
+    # Define our error and OK responses.
+    err409 = exceptions.Aborted(message='derp de derp')
+    err503 = exceptions.ServiceUnavailable(message='whups')
+    errwtf = exceptions.Unknown(message='huh?')
+    ok = showcase_v1alpha3.User(name='users/0', display_name='Guido')
+    server = mock.Mock(side_effect=(err409, err503, errwtf, ok))
+
+    # Mock the transport to send back the error responses followed by a
+    # success response.
+    transport = type(identity).get_transport_class()
+    with mock.patch.object(transport, 'get_user',
+            new_callable=mock.PropertyMock(return_value=server)):
+        with mock.patch.object(time, 'sleep'):
+            response = identity.get_user({'name': 'users/0'})
+        assert response.name == 'users/0'
+        assert response.display_name == 'Guido'
+        assert server.call_count == 4
+
+
+def test_retry_bubble(echo):
+    with pytest.raises(exceptions.DeadlineExceeded):
+        echo.echo({
+            'error': {
+                'code': code_pb2.Code.Value('DEADLINE_EXCEEDED'),
+                'message': 'This took longer than you said it should.',
+            },
+        })

tests/unit/schema/wrappers/test_method.py

@@ -51,10 +51,27 @@ def test_method_field_headers_none():
     assert isinstance(method.field_headers, collections.Sequence)
 
 
-def test_service_field_headers_present():
+def test_method_field_headers_present():
     http_rule = http_pb2.HttpRule(get='/v1/{parent=projects/*}/topics')
-    service = make_method('DoSomething', http_rule=http_rule)
-    assert service.field_headers == ('parent',)
+    method = make_method('DoSomething', http_rule=http_rule)
+    assert method.field_headers == ('parent',)
+
+
+def test_method_idempotent_yes():
+    http_rule = http_pb2.HttpRule(get='/v1/{parent=projects/*}/topics')
+    method = make_method('DoSomething', http_rule=http_rule)
+    assert method.idempotent is True
+
+
+def test_method_idempotent_no():
+    http_rule = http_pb2.HttpRule(post='/v1/{parent=projects/*}/topics')
+    method = make_method('DoSomething', http_rule=http_rule)
+    assert method.idempotent is False
+
+
+def test_method_idempotent_no_http_rule():
+    method = make_method('DoSomething')
+    assert method.idempotent is False
 
 
 def test_method_unary_unary():