grpc-repro.go

package main

import (
	"context"
	"fmt"
	"log"
	"net"

	"google.golang.org/grpc"
	"google.golang.org/grpc/examples/helloworld/helloworld"
)

func main() {
	log.SetFlags(log.LstdFlags | log.Lshortfile)
	ctx := context.Background()

	MustListenAndServe("127.0.0.1:1234")
	MustListenAndServe("127.0.0.2:1234")
	MustListenAndServe("127.0.0.3:1234")

	fmt.Println(MustConnectAndSayHello(ctx, "grpc-test.merovius.de:1234"))
	fmt.Println(MustConnectAndSayHello(ctx, "dns:///grpc-test.merovius.de:1234"))
}

type greeter struct {
	addr string
}

func MustListenAndServe(addr string) {
	l, err := net.Listen("tcp", addr)
	if err != nil {
		log.Fatal(err)
	}
	srv := grpc.NewServer()
	go func() {
		log.Fatal(srv.Serve(l))
	}()
	g := &greeter{addr}
	helloworld.RegisterGreeterServer(srv, g)
}

func (g *greeter) SayHello(ctx context.Context, req *helloworld.HelloRequest) (*helloworld.HelloReply, error) {
	return &helloworld.HelloReply{
		Message: g.addr,
	}, nil
}

func MustConnectAndSayHello(ctx context.Context, target string) []string {
	cc, err := grpc.DialContext(ctx, target, grpc.WithInsecure(), grpc.WithBalancerName("round_robin"))
	if err != nil {
		log.Fatal(err)
	}
	defer cc.Close()
	hc := helloworld.NewGreeterClient(cc)

	var out []string
	for i := 0; i < 9; i++ {
		rep, err := hc.SayHello(ctx, &helloworld.HelloRequest{})
		if err != nil {
			log.Fatal(err)
		}
		out = append(out, rep.Message)
	}
	return out
}