Merge pull request #16252 from mehrdada/python_reflection_docs

Add server reflection guide for Python

doc/csharp/server_reflection.md

@@ -30,7 +30,8 @@ server.Start();
 ```
 
 After starting the server, you can verify that the server reflection
-is working properly by using the `grpc_cli` command line tool:
+is working properly by using the [`grpc_cli` command line
+tool](https://github.com/grpc/grpc/blob/master/doc/command_line_tool.md):
 
  ```sh
   $ grpc_cli ls localhost:50051

doc/python/server_reflection.md

@@ -0,0 +1,61 @@
+# gRPC Python Server Reflection
+
+This document shows how to use gRPC Server Reflection in gRPC Python.
+Please see [C++ Server Reflection Tutorial](../server_reflection_tutorial.md)
+for general information and more examples how to use server reflection.
+
+## Enable server reflection in Python servers
+
+gRPC Python Server Reflection is an add-on library.
+To use it, first install the [grpcio-reflection](https://pypi.org/project/grpcio-reflection/)
+PyPI package into your project.
+
+Note that with Python you need to manually register the service
+descriptors with the reflection service implementation when creating a server
+(this isn't necessary with e.g. C++ or Java)
+```python
+# add the following import statement to use server reflection
+from grpc_reflection.v1alpha import reflection
+# ...
+def serve():
+    server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
+    helloworld_pb2_grpc.add_GreeterServicer_to_server(Greeter(), server)
+    # the reflection service will be aware of "Greeter" and "ServerReflection" services.
+    SERVICE_NAMES = (
+        helloworld_pb2.DESCRIPTOR.services_by_name['Greeter'].full_name,
+        reflection.SERVICE_NAME,
+    )
+    reflection.enable_server_reflection(SERVICE_NAMES, server)
+    server.add_insecure_port('[::]:50051')
+    server.start()
+```
+
+Please see
+[greeter_server_with_reflection.py](https://github.com/grpc/grpc/blob/master/examples/python/helloworld/greeter_server_with_reflection.py)
+in the examples directory for the full example, which extends the gRPC [Python
+`Greeter` example](https://github.com/grpc/tree/master/examples/python/helloworld) on a
+reflection-enabled server.
+
+After starting the server, you can verify that the server reflection
+is working properly by using the [`grpc_cli` command line
+tool](https://github.com/grpc/grpc/blob/master/doc/command_line_tool.md):
+
+ ```sh
+  $ grpc_cli ls localhost:50051
+  ```
+
+  output:
+  ```sh
+  grpc.reflection.v1alpha.ServerReflection
+  helloworld.Greeter
+  ```
+
+  For more examples and instructions how to use the `grpc_cli` tool,
+  please refer to the [`grpc_cli` documentation](../command_line_tool.md)
+  and the [C++ Server Reflection Tutorial](../server_reflection_tutorial.md).
+
+## Additional Resources
+
+The [Server Reflection Protocol](../server-reflection.md) provides detailed
+information about how the server reflection works and describes the server reflection
+protocol in detail.

examples/python/helloworld/greeter_server_with_reflection.py

@@ -0,0 +1,52 @@
+# Copyright 2018 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.
+"""The reflection-enabled version of gRPC helloworld.Greeter server."""
+
+from concurrent import futures
+import time
+
+import grpc
+from grpc_reflection.v1alpha import reflection
+
+import helloworld_pb2
+import helloworld_pb2_grpc
+
+_ONE_DAY_IN_SECONDS = 60 * 60 * 24
+
+
+class Greeter(helloworld_pb2_grpc.GreeterServicer):
+
+    def SayHello(self, request, context):
+        return helloworld_pb2.HelloReply(message='Hello, %s!' % request.name)
+
+
+def serve():
+    server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
+    helloworld_pb2_grpc.add_GreeterServicer_to_server(Greeter(), server)
+    SERVICE_NAMES = (
+        helloworld_pb2.DESCRIPTOR.services_by_name['Greeter'].full_name,
+        reflection.SERVICE_NAME,
+    )
+    reflection.enable_server_reflection(SERVICE_NAMES, server)
+    server.add_insecure_port('[::]:50051')
+    server.start()
+    try:
+        while True:
+            time.sleep(_ONE_DAY_IN_SECONDS)
+    except KeyboardInterrupt:
+        server.stop(0)
+
+
+if __name__ == '__main__':
+    serve()