pkg/logutil: add "NewGRPCLoggerV2FromZapCore"

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

pkg/logutil/zap_grpc.go

@@ -31,6 +31,15 @@ func NewGRPCLoggerV2(lcfg zap.Config) (grpclog.LoggerV2, error) {
 	return &zapGRPCLogger{lg: lg, sugar: lg.Sugar()}, nil
 }
 
+// NewGRPCLoggerV2FromZapCore creates "grpclog.LoggerV2" from "zap.Core"
+// and "zapcore.WriteSyncer". It discards all INFO level logging in gRPC,
+// if debug level is not enabled in "*zap.Logger".
+func NewGRPCLoggerV2FromZapCore(cr zapcore.Core, syncer zapcore.WriteSyncer) grpclog.LoggerV2 {
+	// "AddCallerSkip" to annotate caller outside of "logutil"
+	lg := zap.New(cr, zap.AddCaller(), zap.AddCallerSkip(1), zap.ErrorOutput(syncer))
+	return &zapGRPCLogger{lg: lg, sugar: lg.Sugar()}
+}
+
 type zapGRPCLogger struct {
 	lg    *zap.Logger
 	sugar *zap.SugaredLogger

pkg/logutil/zap_grpc_test.go

@@ -20,10 +20,12 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
 	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 )
 
 func TestNewGRPCLoggerV2(t *testing.T) {
@@ -70,3 +72,20 @@ func TestNewGRPCLoggerV2(t *testing.T) {
 		t.Fatalf("unexpected caller; %q", string(data))
 	}
 }
+
+func TestNewGRPCLoggerV2FromZapCore(t *testing.T) {
+	buf := bytes.NewBuffer(nil)
+	syncer := zapcore.AddSync(buf)
+	cr := zapcore.NewCore(
+		zapcore.NewJSONEncoder(zap.NewProductionEncoderConfig()),
+		syncer,
+		zap.NewAtomicLevelAt(zap.InfoLevel),
+	)
+
+	lg := NewGRPCLoggerV2FromZapCore(cr, syncer)
+	lg.Warning("TestNewGRPCLoggerV2FromZapCore")
+	txt := buf.String()
+	if !strings.Contains(txt, "TestNewGRPCLoggerV2FromZapCore") {
+		t.Fatalf("unexpected log %q", txt)
+	}
+}