From 084c407a8dcc068a1b339f6c809958a08c15b865 Mon Sep 17 00:00:00 2001
From: Gyu-Ho Lee <gyuhox@gmail.com>
Date: Tue, 11 Oct 2016 16:03:29 -0700
Subject: [PATCH] clientv3: drop Config.Logger field

Fix https://github.com/coreos/etcd/issues/6603.

Instead adds 'SetLogger' to set global logger interface
to avoid unnecessary logger updates.
---
 clientv3/client.go       |  8 --------
 clientv3/config.go       |  3 ---
 clientv3/example_test.go |  4 ++++
 clientv3/logger.go       | 40 +++++++++++++++++++++++++++++-----------
 4 files changed, 33 insertions(+), 22 deletions(-)

diff --git a/clientv3/client.go b/clientv3/client.go
index df4ab3478..148addea8 100644
--- a/clientv3/client.go
+++ b/clientv3/client.go
@@ -18,8 +18,6 @@ import (
 	"crypto/tls"
 	"errors"
 	"fmt"
-	"io/ioutil"
-	"log"
 	"net"
 	"net/url"
 	"strings"
@@ -317,12 +315,6 @@ func newClient(cfg *Config) (*Client, error) {
 	client.Watcher = NewWatcher(client)
 	client.Auth = NewAuth(client)
 	client.Maintenance = NewMaintenance(client)
-	if cfg.Logger != nil {
-		logger.Set(cfg.Logger)
-	} else {
-		// disable client side grpc by default
-		logger.Set(log.New(ioutil.Discard, "", 0))
-	}
 
 	go client.autoSync()
 	return client, nil
diff --git a/clientv3/config.go b/clientv3/config.go
index 4f92d7d26..d1d5f4090 100644
--- a/clientv3/config.go
+++ b/clientv3/config.go
@@ -38,9 +38,6 @@ type Config struct {
 	// TLS holds the client secure credentials, if any.
 	TLS *tls.Config
 
-	// Logger is the logger used by client library.
-	Logger Logger
-
 	// Username is a username for authentication
 	Username string
 
diff --git a/clientv3/example_test.go b/clientv3/example_test.go
index 631820282..2c119cb2e 100644
--- a/clientv3/example_test.go
+++ b/clientv3/example_test.go
@@ -20,6 +20,7 @@ import (
 
 	"github.com/coreos/etcd/clientv3"
 	"github.com/coreos/etcd/pkg/transport"
+	"github.com/coreos/pkg/capnslog"
 	"golang.org/x/net/context"
 )
 
@@ -30,6 +31,9 @@ var (
 )
 
 func Example() {
+	var plog = capnslog.NewPackageLogger("github.com/coreos/etcd", "clientv3")
+	clientv3.SetLogger(plog)
+
 	cli, err := clientv3.New(clientv3.Config{
 		Endpoints:   endpoints,
 		DialTimeout: dialTimeout,
diff --git a/clientv3/logger.go b/clientv3/logger.go
index 6e57c4e7c..519db45d8 100644
--- a/clientv3/logger.go
+++ b/clientv3/logger.go
@@ -15,13 +15,15 @@
 package clientv3
 
 import (
+	"io/ioutil"
 	"log"
-	"os"
 	"sync"
 
 	"google.golang.org/grpc/grpclog"
 )
 
+// Logger is the logger used by client library.
+// It implements grpclog.Logger interface.
 type Logger grpclog.Logger
 
 var (
@@ -34,20 +36,36 @@ type settableLogger struct {
 }
 
 func init() {
-	// use go's standard logger by default like grpc
+	// disable client side logs by default
 	logger.mu.Lock()
-	logger.l = log.New(os.Stderr, "", log.LstdFlags)
+	logger.l = log.New(ioutil.Discard, "", 0)
+
+	// logger has to override the grpclog at initialization so that
+	// any changes to the grpclog go through logger with locking
+	// instead of through SetLogger
+	//
+	// now updates only happen through settableLogger.set
 	grpclog.SetLogger(&logger)
 	logger.mu.Unlock()
 }
 
-func (s *settableLogger) Set(l Logger) {
+// SetLogger sets client-side Logger. By default, logs are disabled.
+func SetLogger(l Logger) {
+	logger.set(l)
+}
+
+// GetLogger returns the current logger.
+func GetLogger() Logger {
+	return logger.get()
+}
+
+func (s *settableLogger) set(l Logger) {
 	s.mu.Lock()
 	logger.l = l
 	s.mu.Unlock()
 }
 
-func (s *settableLogger) Get() Logger {
+func (s *settableLogger) get() Logger {
 	s.mu.RLock()
 	l := logger.l
 	s.mu.RUnlock()
@@ -56,9 +74,9 @@ func (s *settableLogger) Get() Logger {
 
 // implement the grpclog.Logger interface
 
-func (s *settableLogger) Fatal(args ...interface{})                 { s.Get().Fatal(args...) }
-func (s *settableLogger) Fatalf(format string, args ...interface{}) { s.Get().Fatalf(format, args...) }
-func (s *settableLogger) Fatalln(args ...interface{})               { s.Get().Fatalln(args...) }
-func (s *settableLogger) Print(args ...interface{})                 { s.Get().Print(args...) }
-func (s *settableLogger) Printf(format string, args ...interface{}) { s.Get().Printf(format, args...) }
-func (s *settableLogger) Println(args ...interface{})               { s.Get().Println(args...) }
+func (s *settableLogger) Fatal(args ...interface{})                 { s.get().Fatal(args...) }
+func (s *settableLogger) Fatalf(format string, args ...interface{}) { s.get().Fatalf(format, args...) }
+func (s *settableLogger) Fatalln(args ...interface{})               { s.get().Fatalln(args...) }
+func (s *settableLogger) Print(args ...interface{})                 { s.get().Print(args...) }
+func (s *settableLogger) Printf(format string, args ...interface{}) { s.get().Printf(format, args...) }
+func (s *settableLogger) Println(args ...interface{})               { s.get().Println(args...) }