clientv3: Enable balancer logging if ETCD_CLIENT_DEBUG environment va…

…riable is set

clientv3/client.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"net"
 	"net/url"
+	"os"
 	"strconv"
 	"strings"
 	"sync"
@@ -49,13 +50,18 @@ var (
 )
 
 func init() {
+	lg := zap.NewNop()
+	if os.Getenv("ETCD_CLIENT_DEBUG") != "" {
+		var err error
+		lg, err = zap.NewProductionConfig().Build() // info level logging
+		if err != nil {
+			panic(err)
+		}
+	}
 	balancer.RegisterBuilder(balancer.Config{
 		Policy: picker.RoundrobinBalanced,
 		Name:   roundRobinBalancerName,
-
-		// TODO: configure from clientv3.Config
-		Logger: zap.NewNop(),
-		// Logger: zap.NewExample(),
+		Logger: lg,
 	})
 }
 

clientv3/config.go

@@ -76,7 +76,7 @@ type Config struct {
 
 	// LogConfig configures client-side logger.
 	// If nil, use the default logger.
-	// TODO: configure balancer and gRPC logger
+	// TODO: configure gRPC logger
 	LogConfig *zap.Config
 }
 

clientv3/doc.go

@@ -99,4 +99,8 @@
 //		}
 //	}
 //
+// The grpc load balancer is registered statically and is shared across etcd clients.
+// To enable detailed load balancer logging, set the ETCD_CLIENT_DEBUG environment
+// variable.  E.g. "ETCD_CLIENT_DEBUG=1".
+//
 package clientv3