pkg/logutil: add "NewRaftLoggerFromZapCore"

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

pkg/logutil/zap_raft.go

@@ -1,8 +1,24 @@
+// Copyright 2018 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package logutil
 
 import (
 	"github.com/coreos/etcd/raft"
+
 	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 )
 
 // NewRaftLogger converts "*zap.Logger" to "raft.Logger".
@@ -14,6 +30,14 @@ func NewRaftLogger(lcfg zap.Config) (raft.Logger, error) {
 	return &zapRaftLogger{lg: lg, sugar: lg.Sugar()}, nil
 }
 
+// NewRaftLoggerFromZapCore creates "raft.Logger" from "zap.Core"
+// and "zapcore.WriteSyncer".
+func NewRaftLoggerFromZapCore(cr zapcore.Core, syncer zapcore.WriteSyncer) raft.Logger {
+	// "AddCallerSkip" to annotate caller outside of "logutil"
+	lg := zap.New(cr, zap.AddCaller(), zap.AddCallerSkip(1), zap.ErrorOutput(syncer))
+	return &zapRaftLogger{lg: lg, sugar: lg.Sugar()}
+}
+
 type zapRaftLogger struct {
 	lg    *zap.Logger
 	sugar *zap.SugaredLogger