Python gRPC + protobufs

Problem

You have .proto files defining protobufs and grpc services and you want Pants to generate Python code from them that you can use from a Python application.

Solution

Create python_grpc_library targets and use the gen goal to generate code from the .proto files. There is a codegen task grpcio-run, that uses Python's grpcio library https://grpc.io/ and generates python code from .proto files.

Usage

in a BUILD file near your proto files, create a python_grpcio_library target with your protos as a sources.

python_grpcio_library(
  sources=['service.proto'],
  dependencies=[
    '3rdparty/python:protobuf',
  ]
)

Then, you can add a dependency on this target in your python binary's BUILD file dependencies section:

python_binary(
  source='server.py',
  dependencies=[
    'src/protobuf/org/pantsbuild/example/grpcio/service',
  ],
)

Example:

An example Python gRPC client/server can be found in /examples/src/python/example/grpcio

to create a gRPC server execute

./pants run src/python/example/grpcio/server

and when server is running, run client example:

./pants run src/python/example/grpcio/client

generated code can be found as usual in pants output directory:

./pants.d/gen/grpcio-run/current/examples.src.protobuf.org.pantsbuild.example.service.service/current/org/pantsbuild/example/service