overflow_service/server/gwrpc.go

package server

import (
	"flag"
	pb "git.loafle.net/overflow/overflow_api_service/grpc"
	"github.com/golang/glog"
	"github.com/grpc-ecosystem/grpc-gateway/runtime"
	"golang.org/x/net/context"
	"google.golang.org/grpc"
	"net/http"
	"strings"
)

var (
	overflowEndpoint = flag.String("echo_endpoint", ":9090", "/v1/overflow/services")
)

func RunGwRpc() (err error) {
	ctx := context.Background()
	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	mux := runtime.NewServeMux()
	opts := []grpc.DialOption{grpc.WithInsecure()}

	err = pb.RegisterOverflowGatewayHandlerFromEndpoint(ctx, mux, *overflowEndpoint, opts)

	if err != nil {
		return err
	}

	return http.ListenAndServe(":8080", allowCORS(mux))
}

//https://github.com/grpc-ecosystem/grpc-gateway/blob/master/examples/main.go

func allowCORS(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if origin := r.Header.Get("Origin"); origin != "" {
			w.Header().Set("Access-Control-Allow-Origin", origin)
			if r.Method == "OPTIONS" && r.Header.Get("Access-Control-Request-Method") != "" {
				preflightHandler(w, r)
				return
			}
		}
		h.ServeHTTP(w, r)
	})
}

func preflightHandler(w http.ResponseWriter, r *http.Request) {
	headers := []string{"Content-Type", "Accept"}
	w.Header().Set("Access-Control-Allow-Headers", strings.Join(headers, ","))
	methods := []string{"GET", "HEAD", "POST", "PUT", "DELETE"}
	w.Header().Set("Access-Control-Allow-Methods", strings.Join(methods, ","))
	glog.Infof("preflight request for %s", r.URL.Path)
	return
}