grpc-web + golang

https://github.com/grpc/grpc-web

let's create our demo

prerequisites

• protoc ( this is doing the proto parsing magic and comes with bunch of default compilers ootb : https://github.com/protocolbuffers/protobuf/releases)
• protoc-gen-go ( plugin to generate go code from proto : https://github.com/golang/protobuf )
• protoc-gen-grpc-web ( plugin to create javascript grpc stub : https://github.com/grpc/grpc-web/releases )
• npm ( get out javascript dependencies )
• webpack / webpack-cli ( bundle dependencies of gprc-web + own client into a single file )
• envoy ( proxy grpc-web traffic to the grpc server )

steps

• create a new project

    go mod init github.com/mier85/grpc-web-example
  

• create a protobuf contract

    mkdir contract
    touch contract/contract.proto
  

• now let's create the corresponding sources:

    # use protoc, generate go files including the grpc stub and make the path relative to where it should be
    protoc --go_out=plugins=grpc,paths=source_relative:. contract/contract.proto        
  

• now let's build the service. first we need to get some dependencies

   # in this step we download half of the internet
   go get -u google.golang.org/grpc
   
   # we don't need this, but it'll give us some nice extras
   go get -u github.com/grpc-ecosystem/go-grpc-middleware
   
   # get some logs going for us
   go get -u go.uber.org/zap
  

• now let's create the web stuff

  # create the folders that we will need
  mkdir -p js/src/contract
  
  # similar to what we did with the go source, let's create the js sources now 
  protoc -I=./contract contract/contract.proto --js_out=import_style=commonjs:js/src/contract --grpc-web_out=import_style=commonjs,mode=grpcweb:js/src/contract
  
  cd js
  
  # now let's get to the hacky part, use webpack to create js that we can load inside the server
  npm init -y
  npm install --save-dev npx google-protobuf grpc-web webpack webpack-cli
  
  # create our client
  npx webpack --mode=development --output-library="grpcwebexample"  
  

• let's get it running

    # last but not least, we need to proxy the web-request to the web endpoint 
    docker build -f Dockerfile.envoy -t grpcwebexample/envoy .
    docker run --net=host grpcwebexample/envoy