Adopt review's advice

* Add a unit test
* Integrate with Bazel
* Polish README.md

examples/protos/BUILD.bazel

+# Copyright 2019 The gRPC Authors
+#
+# 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
+#
+#     http://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.
+
+load("@grpc_python_dependencies//:requirements.bzl", "requirement")
+load("@org_pubref_rules_protobuf//python:rules.bzl", "py_proto_library")
+
+package(default_visibility = ["//visibility:public"])
+
+py_proto_library(
+    name = "py_helloworld_proto",
+    protos = ["helloworld.proto",],
+    with_grpc = True,
+    deps = [requirement('protobuf'),],
+)

examples/python/errors/BUILD.bazel

+# Copyright 2019 The gRPC Authors
+#
+# 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
+#
+#     http://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.
+
+load("@grpc_python_dependencies//:requirements.bzl", "requirement")
+load("@org_pubref_rules_protobuf//python:rules.bzl", "py_proto_library")
+
+py_library(
+    name = "client",
+    testonly = 1,
+    srcs = ["client.py"],
+    deps = [
+        "//src/python/grpcio/grpc:grpcio",
+        "//src/python/grpcio_status/grpc_status:grpc_status",
+        "//examples/protos:py_helloworld_proto",
+        requirement('googleapis-common-protos'),
+    ],
+)
+
+py_library(
+    name = "server",
+    testonly = 1,
+    srcs = ["server.py"],
+    deps = [
+        "//src/python/grpcio/grpc:grpcio",
+        "//src/python/grpcio_status/grpc_status:grpc_status",
+        "//examples/protos:py_helloworld_proto",
+    ] + select({
+        "//conditions:default": [requirement("futures")],
+        "//:python3": [],
+    }),
+)
+
+py_test(
+    name = "test/_error_handling_example_test",
+    srcs = ["test/_error_handling_example_test.py"],
+    data = [
+        ":client",
+        ":server",
+        "//src/python/grpcio_tests/tests:bazel_namespace_package_hack",
+    ],
+    size = "small",
+    imports = ["../../../src/python/grpcio_status",],
+)

examples/python/errors/README.md

@@ -6,8 +6,27 @@ The definition for an RPC method in proto files contains request message and res
 
 Ideally, the final status of an RPC should be described in the trailing headers of HTTP2, and gRPC Python provides helper functions in `grpcio-status` package to assist the packing and unpacking of error status.
 
+
+### Requirement
+```
+grpcio>=1.18.0
+grpcio-status>=1.18.0
+googleapis-common-protos>=1.5.5
+```
+
+
+### Error Detail Proto
+
+You may provide any custom proto message as error detail in your implementation. Here are protos are defined by Google Cloud Library Team:
+
+* [code.proto](https://github.com/googleapis/api-common-protos/blob/master/google/rpc/code.proto) contains definition of RPC error codes.
+* [error_details.proto](https://github.com/googleapis/api-common-protos/blob/master/google/rpc/error_details.proto) contains definitions of common error details.
+
+
 ### Definition of Status Proto
 
+Here is the definition of Status proto. For full text, please see [status.proto](https://github.com/googleapis/api-common-protos/blob/master/google/rpc/status.proto).
+
 ```proto
 // The `Status` type defines a logical error model that is suitable for different
 // programming environments, including REST APIs and RPC APIs. It is used by
@@ -76,6 +95,7 @@ message Status {
 }
 ```
 
+
 ### Usage of Well-Known-Proto `Any`
 
 Please check [ProtoBuf Document: Any](https://developers.google.com/protocol-buffers/docs/reference/python-generated#any)
@@ -85,12 +105,3 @@ any_message.Pack(message)
 any_message.Unpack(message)
 assert any_message.Is(message.DESCRIPTOR)
 ```
-
-### Common Protos
-
-These protos are defined by Google Cloud API. Most error cases are covered in `error_dettails.proto`, but you may provide any custom error detail proto you want.
-
-Please refer to:
-* [code.proto](https://github.com/googleapis/api-common-protos/blob/master/google/rpc/code.proto).
-* [status.proto](https://github.com/googleapis/api-common-protos/blob/master/google/rpc/status.proto).
-* [error_details.proto](https://github.com/googleapis/api-common-protos/blob/master/google/rpc/error_details.proto).

examples/python/errors/error_handling_client.py → examples/python/errors/client.py

@@ -20,31 +20,37 @@ import grpc
 from grpc_status import rpc_status
 from google.rpc import error_details_pb2
 
-import helloworld_pb2
-import helloworld_pb2_grpc
+from examples.protos import helloworld_pb2
+from examples.protos import helloworld_pb2_grpc
 
+_LOGGER = logging.getLogger(__name__)
 
-def run():
+
+def process(stub):
+    try:
+        response = stub.SayHello(helloworld_pb2.HelloRequest(name='Alice'))
+        _LOGGER.info('Call success: %s', response.message)
+    except grpc.RpcError as rpc_error:
+        _LOGGER.error('Call failure: %s', rpc_error)
+        status = rpc_status.from_call(rpc_error)
+        for detail in status.details:
+            if detail.Is(error_details_pb2.QuotaFailure.DESCRIPTOR):
+                info = error_details_pb2.QuotaFailure()
+                detail.Unpack(info)
+                _LOGGER.error('Quota failure: %s', info)
+            else:
+                raise RuntimeError('Unexpected failure: %s' % detail)
+
+
+def main():
     # NOTE(gRPC Python Team): .close() is possible on a channel and should be
     # used in circumstances in which the with statement does not fit the needs
     # of the code.
     with grpc.insecure_channel('localhost:50051') as channel:
         stub = helloworld_pb2_grpc.GreeterStub(channel)
-        try:
-            response = stub.SayHello(helloworld_pb2.HelloRequest(name='Alice'))
-            print('Call success:', response.message)
-        except grpc.RpcError as rpc_error:
-            print('Call failure:', rpc_error)
-            status = rpc_status.from_call(rpc_error)
-            for detail in status.details:
-                if detail.Is(error_details_pb2.QuotaFailure.DESCRIPTOR):
-                    info = error_details_pb2.QuotaFailure()
-                    detail.Unpack(info)
-                    print('Quota failure:', info)
-                else:
-                    print('Unexpected failure:', detail)
+        process(stub)
 
 
 if __name__ == '__main__':
     logging.basicConfig()
-    run()
+    main()

examples/python/errors/helloworld_pb2.py

-# Generated by the protocol buffer compiler.  DO NOT EDIT!
-# source: helloworld.proto
-
-import sys
-_b=sys.version_info[0]<3 and (lambda x:x) or (lambda x:x.encode('latin1'))
-from google.protobuf import descriptor as _descriptor
-from google.protobuf import message as _message
-from google.protobuf import reflection as _reflection
-from google.protobuf import symbol_database as _symbol_database
-from google.protobuf import descriptor_pb2
-# @@protoc_insertion_point(imports)
-
-_sym_db = _symbol_database.Default()
-
-
-
-
-DESCRIPTOR = _descriptor.FileDescriptor(
-  name='helloworld.proto',
-  package='helloworld',
-  syntax='proto3',
-  serialized_pb=_b('\n\x10helloworld.proto\x12\nhelloworld\"\x1c\n\x0cHelloRequest\x12\x0c\n\x04name\x18\x01 \x01(\t\"\x1d\n\nHelloReply\x12\x0f\n\x07message\x18\x01 \x01(\t2I\n\x07Greeter\x12>\n\x08SayHello\x12\x18.helloworld.HelloRequest\x1a\x16.helloworld.HelloReply\"\x00\x42\x36\n\x1bio.grpc.examples.helloworldB\x0fHelloWorldProtoP\x01\xa2\x02\x03HLWb\x06proto3')
-)
-
-
-
-
-_HELLOREQUEST = _descriptor.Descriptor(
-  name='HelloRequest',
-  full_name='helloworld.HelloRequest',
-  filename=None,
-  file=DESCRIPTOR,
-  containing_type=None,
-  fields=[
-    _descriptor.FieldDescriptor(
-      name='name', full_name='helloworld.HelloRequest.name', index=0,
-      number=1, type=9, cpp_type=9, label=1,
-      has_default_value=False, default_value=_b("").decode('utf-8'),
-      message_type=None, enum_type=None, containing_type=None,
-      is_extension=False, extension_scope=None,
-      options=None),
-  ],
-  extensions=[
-  ],
-  nested_types=[],
-  enum_types=[
-  ],
-  options=None,
-  is_extendable=False,
-  syntax='proto3',
-  extension_ranges=[],
-  oneofs=[
-  ],
-  serialized_start=32,
-  serialized_end=60,
-)
-
-
-_HELLOREPLY = _descriptor.Descriptor(
-  name='HelloReply',
-  full_name='helloworld.HelloReply',
-  filename=None,
-  file=DESCRIPTOR,
-  containing_type=None,
-  fields=[
-    _descriptor.FieldDescriptor(
-      name='message', full_name='helloworld.HelloReply.message', index=0,
-      number=1, type=9, cpp_type=9, label=1,
-      has_default_value=False, default_value=_b("").decode('utf-8'),
-      message_type=None, enum_type=None, containing_type=None,
-      is_extension=False, extension_scope=None,
-      options=None),
-  ],
-  extensions=[
-  ],
-  nested_types=[],
-  enum_types=[
-  ],
-  options=None,
-  is_extendable=False,
-  syntax='proto3',
-  extension_ranges=[],
-  oneofs=[
-  ],
-  serialized_start=62,
-  serialized_end=91,
-)
-
-DESCRIPTOR.message_types_by_name['HelloRequest'] = _HELLOREQUEST
-DESCRIPTOR.message_types_by_name['HelloReply'] = _HELLOREPLY
-_sym_db.RegisterFileDescriptor(DESCRIPTOR)
-
-HelloRequest = _reflection.GeneratedProtocolMessageType('HelloRequest', (_message.Message,), dict(
-  DESCRIPTOR = _HELLOREQUEST,
-  __module__ = 'helloworld_pb2'
-  # @@protoc_insertion_point(class_scope:helloworld.HelloRequest)
-  ))
-_sym_db.RegisterMessage(HelloRequest)
-
-HelloReply = _reflection.GeneratedProtocolMessageType('HelloReply', (_message.Message,), dict(
-  DESCRIPTOR = _HELLOREPLY,
-  __module__ = 'helloworld_pb2'
-  # @@protoc_insertion_point(class_scope:helloworld.HelloReply)
-  ))
-_sym_db.RegisterMessage(HelloReply)
-
-
-DESCRIPTOR.has_options = True
-DESCRIPTOR._options = _descriptor._ParseOptions(descriptor_pb2.FileOptions(), _b('\n\033io.grpc.examples.helloworldB\017HelloWorldProtoP\001\242\002\003HLW'))
-
-_GREETER = _descriptor.ServiceDescriptor(
-  name='Greeter',
-  full_name='helloworld.Greeter',
-  file=DESCRIPTOR,
-  index=0,
-  options=None,
-  serialized_start=93,
-  serialized_end=166,
-  methods=[
-  _descriptor.MethodDescriptor(
-    name='SayHello',
-    full_name='helloworld.Greeter.SayHello',
-    index=0,
-    containing_service=None,
-    input_type=_HELLOREQUEST,
-    output_type=_HELLOREPLY,
-    options=None,
-  ),
-])
-_sym_db.RegisterServiceDescriptor(_GREETER)
-
-DESCRIPTOR.services_by_name['Greeter'] = _GREETER
-
-# @@protoc_insertion_point(module_scope)

examples/python/errors/helloworld_pb2_grpc.py

-# Generated by the gRPC Python protocol compiler plugin. DO NOT EDIT!
-import grpc
-
-import helloworld_pb2 as helloworld__pb2
-
-
-class GreeterStub(object):
-  """The greeting service definition.
-  """
-
-  def __init__(self, channel):
-    """Constructor.
-
-    Args:
-      channel: A grpc.Channel.
-    """
-    self.SayHello = channel.unary_unary(
-        '/helloworld.Greeter/SayHello',
-        request_serializer=helloworld__pb2.HelloRequest.SerializeToString,
-        response_deserializer=helloworld__pb2.HelloReply.FromString,
-        )
-
-
-class GreeterServicer(object):
-  """The greeting service definition.
-  """
-
-  def SayHello(self, request, context):
-    """Sends a greeting
-    """
-    context.set_code(grpc.StatusCode.UNIMPLEMENTED)
-    context.set_details('Method not implemented!')
-    raise NotImplementedError('Method not implemented!')
-
-
-def add_GreeterServicer_to_server(servicer, server):
-  rpc_method_handlers = {
-      'SayHello': grpc.unary_unary_rpc_method_handler(
-          servicer.SayHello,
-          request_deserializer=helloworld__pb2.HelloRequest.FromString,
-          response_serializer=helloworld__pb2.HelloReply.SerializeToString,
-      ),
-  }
-  generic_handler = grpc.method_handlers_generic_handler(
-      'helloworld.Greeter', rpc_method_handlers)
-  server.add_generic_rpc_handlers((generic_handler,))

examples/python/errors/error_handling_server.py → examples/python/errors/server.py

@@ -24,8 +24,8 @@ from grpc_status import rpc_status
 from google.protobuf import any_pb2
 from google.rpc import code_pb2, status_pb2, error_details_pb2
 
-import helloworld_pb2
-import helloworld_pb2_grpc
+from examples.protos import helloworld_pb2
+from examples.protos import helloworld_pb2_grpc
 
 _ONE_DAY_IN_SECONDS = 60 * 60 * 24
 
@@ -36,7 +36,7 @@ def create_greet_limit_exceed_error_status(name):
         error_details_pb2.QuotaFailure(
             violations=[
                 error_details_pb2.QuotaFailure.Violation(
-                    subject="name:%s" % name,
+                    subject="name: %s" % name,
                     description="Limit one greeting per person",
                 )
             ],))
@@ -64,10 +64,14 @@ class LimitedGreeter(helloworld_pb2_grpc.GreeterServicer):
         return helloworld_pb2.HelloReply(message='Hello, %s!' % request.name)
 
 
-def serve():
+def create_server(server_address):
     server = grpc.server(futures.ThreadPoolExecutor())
     helloworld_pb2_grpc.add_GreeterServicer_to_server(LimitedGreeter(), server)
-    server.add_insecure_port('[::]:50051')
+    port = server.add_insecure_port(server_address)
+    return server, port
+
+
+def serve(server):
     server.start()
     try:
         while True:
@@ -76,6 +80,11 @@ def serve():
         server.stop(None)
 
 
+def main():
+    server, unused_port = create_server('[::]:50051')
+    serve(server)
+
+
 if __name__ == '__main__':
     logging.basicConfig()
-    serve()
+    main()

examples/python/errors/test/_error_handling_example_test.py

+# Copyright 2019 The gRPC Authors
+#
+# 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
+#
+#     http://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.
+"""Tests of the error handling example."""
+
+import unittest
+import logging
+
+import grpc
+
+from examples.protos import helloworld_pb2_grpc
+from examples.python.errors import client as error_handling_client
+from examples.python.errors import server as error_handling_server
+
+# NOTE(lidiz) This module only exists in Bazel BUILD file, for more details
+# please refer to comments in the "bazel_namespace_package_hack" module.
+try:
+    from tests import bazel_namespace_package_hack
+    bazel_namespace_package_hack.sys_path_to_site_dir_hack()
+except ImportError:
+    pass
+
+
+class ErrorHandlingExampleTest(unittest.TestCase):
+
+    def setUp(self):
+        self._server, port = error_handling_server.create_server('[::]:0')
+        self._server.start()
+        self._channel = grpc.insecure_channel('localhost:%d' % port)
+
+    def tearDown(self):
+        self._channel.close()
+        self._server.stop(None)
+
+    def test_error_handling_example(self):
+        stub = helloworld_pb2_grpc.GreeterStub(self._channel)
+        error_handling_client.process(stub)
+        error_handling_client.process(stub)
+        # No unhandled exception raised, test passed!
+
+
+if __name__ == '__main__':
+    logging.basicConfig()
+    unittest.main(verbosity=2)

src/python/grpcio_tests/tests/BUILD.bazel

@@ -4,5 +4,6 @@ py_library(
     visibility = [
         "//src/python/grpcio_tests/tests/status:__subpackages__",
         "//src/python/grpcio_tests/tests/interop:__subpackages__",
+        "//examples/python/errors:__subpackages__",
     ],
 )