gRPC HTTP annotations for Go

A Go implementation of gRPC to HTTP/JSON transcoding using Google's HTTP Protobuf annotations.

To use, define a gRPC service with HTTP bindings:

syntax = "proto3";

// ...

import "google/api/annotations.proto";

service Test {
  rpc GetItem(GetItemRequest) returns(Item) {
    option (google.api.http) = { 
      get: "/v1/items/{name=*}"
    };
  } 
}

message Item {
  string name = 1;
  int64 id = 2;
}

message GetItemRequest {
  string name = 1;
}

Generate the Protobuf and gRPC packages using gRPC's Go support. After implememeting the service, the grpchttp package can be used to create a net/http.Handler:

package main

import (
    "context"
    "log"
    "net/http"

    "github.com/ericchiang/grpc-http-go/grpchttp"

    pb "example.com/testservice"
)

type service struct {}

func (s *service) GetItem(ctx context.Context, req *pb.GetItemRequest) (*pb.Item, error) {
    return &pb.Item{Name: req.GetName(), Id: 42}, nil
}

func main() {
    srv := &service{}
    hander, err := grpchttp.NewHandler(&pb.Test_ServiceDesc, srv)
    if err != nil {
        log.Fatalf("creating HTTP handler: %v", err)
    }
    log.Fatal(http.ListenAndServe(":8080", handler))
}

Request and responses will automatically be converted using the annotation rules and Protobuf's JSON support:

$ curl -s http://localhost:8080/v1/items/myitem | jq .
{
  "name": "myitem",
  "id": "42"
}

This project is compariable to gRPC to HTTP/JSON support that exists gRPC-Gateway and Envoy, which are aim at larger scale deployments of gRPC services. The grpchttp package aims to be a good solution for single binaries written in Go to quickly support HTTP bindings without custom proto generators.