etcdserver,embed: discard gRPC info logs when debug is off

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

etcdserver/api/v3rpc/grpc.go

@@ -16,6 +16,7 @@ package v3rpc
 
 import (
 	"crypto/tls"
+	"io/ioutil"
 	"math"
 	"os"
 
@@ -36,10 +37,6 @@ const (
 	maxSendBytes      = math.MaxInt32
 )
 
-func init() {
-	grpclog.SetLoggerV2(grpclog.NewLoggerV2(os.Stderr, os.Stderr, os.Stderr))
-}
-
 func Server(s *etcdserver.EtcdServer, tls *tls.Config, gopts ...grpc.ServerOption) *grpc.Server {
 	var opts []grpc.ServerOption
 	opts = append(opts, grpc.CustomCodec(&codec{}))
@@ -70,5 +67,13 @@ func Server(s *etcdserver.EtcdServer, tls *tls.Config, gopts ...grpc.ServerOptio
 	// set zero values for metrics registered for this grpc server
 	grpc_prometheus.Register(grpcServer)
 
+	if s.Cfg.Debug {
+		grpc.EnableTracing = true
+		// enable info, warning, error
+		grpclog.SetLoggerV2(grpclog.NewLoggerV2(os.Stderr, os.Stderr, os.Stderr))
+	} else {
+		// only discard info
+		grpclog.SetLoggerV2(grpclog.NewLoggerV2(ioutil.Discard, os.Stderr, os.Stderr))
+	}
 	return grpcServer
 }