gRPC example code

Background

I'm brushing up on modern Web API technologies, including gRPC and OpenAPI. This example has been useful to me (once I got it working) so I'm checkpointing it and making it available publicly - hope its also useful to others!

See also:

• Basic tutorial for Python gRPC: https://www.velotio.com/engineering-blog/grpc-implementation-using-python
• Information about grpc-gateway: https://github.com/grpc-ecosystem/grpc-gateway/

Things I would like to improve:

• google/ directory containing a copy of some proto definitions should be moved under proto/third_party;
• Python auto generated code should go under src/python_grpc/autogenerated, not src/python_grpc/;

Working with the code

Docker

Tested with Docker version 18.03.1-ce, build 9ee9f40. Note TLS is enabled when running via Docker.

Build image

./docker-build.sh

Run it

./docker-run.sh

Manually

Tested with Python 3.7.3 and go1.17.5 on linux/amd64.

Use commands below in sequence to generate required code from the proto definition and start/test the gRPC and REST proxy services.

Clean up all generated files

rm -rf src/go_rest_proxy/autogenerated/*
rm -rf src/python_grpc/proto
rm -rf src/python_grpc/google
rm -f go.mod go.sum
rm -f rest_reverse_proxy

Generate proto code for Python

python -m grpc_tools.protoc \
  -I=. \
  --python_out=./src/python_grpc \
  --grpc_python_out=./src/python_grpc \
  ./google/api/http.proto ./google/api/annotations.proto \
  ./proto/unary.proto

Start Python gRPC server in the background

python src/python_grpc/server.py &

Run Python gRPC client to test the server

python src/python_grpc/client.py

Generate proto code for Go

protoc \
  -I=. \
  --go_out ./src/go_rest_proxy/autogenerated/ --go_opt paths=source_relative \
  --go-grpc_out ./src/go_rest_proxy/autogenerated/ --go-grpc_opt paths=source_relative \
  --grpc-gateway_out ./src/go_rest_proxy/autogenerated/ \
  --grpc-gateway_opt logtostderr=true \
  --grpc-gateway_opt paths=source_relative \
  ./proto/unary.proto

Create Go module for the autogenerated proto code

cd src/go_rest_proxy/autogenerated/proto/
go mod init github.com/thiagorobert/grpc-example/autogenerated_proto
go mod tidy
cd -

Create Go module for the REST reverse proxy

go mod init github.com/thiagorobert/grpc-example
echo "replace github.com/thiagorobert/grpc-example/autogenerated_proto => ./src/go_rest_proxy/autogenerated/proto/" >> go.mod
go mod tidy -compat=1.17

Build REST proxy

go build src/go_rest_proxy/rest_reverse_proxy.go

Start REST proxy in the background

./rest_reverse_proxy &

Query REST API

curl -X POST localhost:8081/v1/response -d '{"message": "test"}'

TLS

Use flag --cert_path to enable TLS. Note the Python gRPC server will also require flag --private_key_path. TLS data (certificate, private key) is available under tls_data directory.