Repository: grpc/grpc-go
File: examples/features/opentelemetry/server/main.go (Go)

Code before:
	"flag"
	"log"
	"net"
	"net/http"

	"google.golang.org/grpc"
	pb "google.golang.org/grpc/examples/helloworld/helloworld"
	"google.golang.org/grpc/stats/opentelemetry"

	"github.com/prometheus/client_golang/prometheus/promhttp"
	"go.opentelemetry.io/otel/exporters/prometheus"
	"go.opentelemetry.io/otel/sdk/metric"
)

var (
	addr               = flag.String("addr", ":50051", "the server address to connect to")
	prometheusEndpoint = flag.String("prometheus_endpoint", ":9464", "the Prometheus exporter endpoint")
)

type server struct {
	pb.UnimplementedGreeterServer
	addr string
}

// SayHello implements helloworld.GreeterServer
func (s *server) SayHello(_ context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	log.Printf("Received: %v", in.GetName())
	return &pb.HelloReply{Message: "Hello " + in.GetName()}, nil
}

func main() {
	exporter, err := prometheus.New()
	if err != nil {
		log.Fatalf("Failed to start prometheus exporter: %v", err)
	}
	provider := metric.NewMeterProvider(metric.WithReader(exporter))
	go http.ListenAndServe(*prometheusEndpoint, promhttp.Handler())

	so := opentelemetry.ServerOption(opentelemetry.Options{MetricsOptions: opentelemetry.MetricsOptions{MeterProvider: provider}})

	lis, err := net.Listen("tcp", *addr)
	if err != nil {
		log.Fatalf("Failed to listen: %v", err)
	}
	s := grpc.NewServer(so)
	pb.RegisterGreeterServer(s, &server{addr: *addr})

	log.Printf("Serving on %s\n", *addr)

	if err := s.Serve(lis); err != nil {
		log.Fatalf("Failed to serve: %v", err)

Review comment (suggestion):
`SayHello` is a method, it's inaccurate to say that it implements an interface. I believe this comment should be on `server` instead.

Code after:
	"flag"
	"fmt"
	"log"
	"net"
	"net/http"

	"google.golang.org/grpc"
	pb "google.golang.org/grpc/examples/features/proto/echo"
	"google.golang.org/grpc/stats/opentelemetry"

	"github.com/prometheus/client_golang/prometheus/promhttp"
	"go.opentelemetry.io/otel/exporters/prometheus"
	"go.opentelemetry.io/otel/sdk/metric"
)

var (
	addr               = flag.String("addr", ":50051", "the server address to connect to")
	prometheusEndpoint = flag.String("prometheus_endpoint", ":9464", "the Prometheus exporter endpoint")
)

type echoServer struct {
	pb.UnimplementedEchoServer
	addr string
}

func (s *echoServer) UnaryEcho(_ context.Context, req *pb.EchoRequest) (*pb.EchoResponse, error) {
	return &pb.EchoResponse{Message: fmt.Sprintf("%s (from %s)", req.Message, s.addr)}, nil
}

func main() {
	exporter, err := prometheus.New()
	if err != nil {
		log.Fatalf("Failed to start prometheus exporter: %v", err)
	}
	provider := metric.NewMeterProvider(metric.WithReader(exporter))
	go http.ListenAndServe(*prometheusEndpoint, promhttp.Handler())

	so := opentelemetry.ServerOption(opentelemetry.Options{MetricsOptions: opentelemetry.MetricsOptions{MeterProvider: provider}})

	lis, err := net.Listen("tcp", *addr)
	if err != nil {
		log.Fatalf("Failed to listen: %v", err)
	}
	s := grpc.NewServer(so)
	pb.RegisterEchoServer(s, &echoServer{addr: *addr})

	log.Printf("Serving on %s\n", *addr)

	if err := s.Serve(lis); err != nil {
		log.Fatalf("Failed to serve: %v", err)
	}