gRPC Tutorial + Swagger JSON

Basic tutorial into setting up a gRPC reverse proxy that will
transform REST JSON into gRPC, along with instructions on how
to generate Swagger definitions.
Instructions on how to run client/server in other languages.

Goals

• service defintion in service.proto
• generate client and server code using protoc.
• wrap generated code to expose light client (and server).
• generate gateway code for HTTP/JSON reverse proxy.

TODO

• get Swagger UI to render service’s Swagger JSON (with auth)
• auth definitions in proto
• investigate python reverse proxy support #398
• write up instructions for java {grpc-jersey}
• find a contributor for nodejs

Basic Setup

• use gvm or something to get Go >= 1.6
• brew install protobuf or apt install libprotobuf-dev
• $ go help gopath # make sure GOPATH is set

Golang installations

go get google.golang.org/grpc
go get -u github.com/golang/protobuf/proto
go get -u github.com/golang/protobuf/protoc-gen-go
go get -u github.com/grpc-ecosystem/grpc-gateway/protoc-gen-grpc-gateway
go get -u github.com/grpc-ecosystem/grpc-gateway/protoc-gen-swagger

Architecture

This is the basic architecture of a grpc-gateway application {from grpc-ecosystem/grpc-gateway/}.

Service definition

pb/service.proto

Golang Client/Server code generation

pb/service.pb.go

To generate:

$ protoc -I/usr/local/include -I. \
  -I$GOPATH/src \
  -I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
  --go_out=google/api/annotations.proto=github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis/google/api,plugins=grpc:. \
  pb/service.proto

Golang Reverse proxy gateway code generation

pb/service.pb.gw.go

To generate:

$ protoc -I/usr/local/include -I. \
   -I$GOPATH/src \
   -I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
   --grpc-gateway_out=logtostderr=true:. \
   pb/service.proto

Golang Client code

client/client.go

Golang Server code

server/server.go

Golang Reverse proxy server code

server/server-rproxy.go

Golang Server <-> Client communication

go run server/server.go
...
go run client/client.go

Will display 2018/05/28 12:57:11 Hello debo!

Golang Server <-> Client via gRPC Gateway

go run server/server.go
...
go run server/server-rproxy.go
...
curl -X POST "http://localhost:8080/v1/example/hello/v1/world" | jq .

Will display

{
  "id": "v1",
  "msg": "world"
}

Python Client/Server code generation

PR to update gRPC docs: #671
pb/service_pb2.py
pb/service_pb2_grpc.py

To generate:

virtualenv env
. env/bin/activate
pip install grpcio-tools googleapis-common-protos
python -m grpc_tools.protoc --python_out=. \
  --grpc_python_out=. -I. -I/usr/local/include \
  -I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
  -I/usr/local/include \
  pb/service.proto

Python Client code

client/client.py

Python Server code

server/server.py

Python Server <-> Client communication

python -m server.server
...
python -m client.client

Will display Hello world!

Python Reverse proxy server code

I don’t believe this can be done in the state of the world at the time of writing.

Generate Swagger JSON

pb/service.swagger.json

To generate:

protoc -I/usr/local/include -I. \
  -I$GOPATH/src \
  -I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis \
  --swagger_out=logtostderr=true:. \
  pb/service.proto