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Add server reflection guide for Python
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mehrdada committed Aug 6, 2018
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61 changes: 61 additions & 0 deletions doc/python/server_reflection.md
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# 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.
52 changes: 52 additions & 0 deletions examples/python/helloworld/greeter_server_with_reflection.py
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# 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()

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