diff --git a/blobstore/common/trace/span.go b/blobstore/common/trace/span.go
index 2bcdb4a7e9..7636668cf7 100644
--- a/blobstore/common/trace/span.go
+++ b/blobstore/common/trace/span.go
@@ -295,11 +295,11 @@ const (
 )
 
 func (s *spanImpl) output(lvl log.Level, v []interface{}) {
-	log.DefaultLogger.Output(s.String(), lvl, defaultCalldepth, fmt.Sprintln(v...))
+	log.DefaultLogger.Output(s.String(), lvl, defaultCalldepth, v...)
 }
 
 func (s *spanImpl) outputf(lvl log.Level, format string, v []interface{}) {
-	log.DefaultLogger.Output(s.String(), lvl, defaultCalldepth, fmt.Sprintf(format, v...))
+	log.DefaultLogger.Outputf(s.String(), lvl, defaultCalldepth, format, v...)
 }
 
 func (s *spanImpl) Println(v ...interface{})               { s.output(log.Linfo, v) }
diff --git a/blobstore/util/log/log.go b/blobstore/util/log/log.go
index 055c6e6b75..af64ab87f9 100644
--- a/blobstore/util/log/log.go
+++ b/blobstore/util/log/log.go
@@ -115,7 +115,8 @@ type Logger interface {
 	GetOutputLevel() Level
 	SetOutputLevel(logLevel Level)
 	SetOutput(w io.Writer)
-	Output(id string, lvl Level, calldepth int, s string) error
+	Output(id string, lvl Level, calldepth int, a ...interface{}) error
+	Outputf(id string, lvl Level, calldepth int, format string, a ...interface{}) error
 
 	// implement raft Logger with these two function
 	Warningf(format string, v ...interface{})
diff --git a/blobstore/util/log/logext.go b/blobstore/util/log/logext.go
index 03778cacd5..414b91b2fc 100644
--- a/blobstore/util/log/logext.go
+++ b/blobstore/util/log/logext.go
@@ -52,19 +52,34 @@ func New(out io.Writer, calldepth int) Logger {
 	return l
 }
 
-func (l *logger) Output(id string, lvl Level, calldepth int, s string) error {
+func (l *logger) Output(id string, lvl Level, calldepth int, a ...interface{}) error {
 	if int32(lvl) < atomic.LoadInt32(&l.level) || lvl >= maxLevel {
 		return nil
 	}
+	_, file, line, ok := runtime.Caller(calldepth)
+	if !ok {
+		file = "???"
+		line = 0
+	}
+	return l.write(id, lvl, file, line, fmt.Sprintln(a...))
+}
 
-	now := time.Now()
-	buf := l.pool.Get().(*bytes.Buffer)
-
+func (l *logger) Outputf(id string, lvl Level, calldepth int, format string, a ...interface{}) error {
+	if int32(lvl) < atomic.LoadInt32(&l.level) || lvl >= maxLevel {
+		return nil
+	}
 	_, file, line, ok := runtime.Caller(calldepth)
 	if !ok {
 		file = "???"
 		line = 0
 	}
+	return l.write(id, lvl, file, line, fmt.Sprintf(format, a...))
+}
+
+func (l *logger) write(id string, lvl Level, file string, line int, s string) error {
+	now := time.Now()
+	buf := l.pool.Get().(*bytes.Buffer)
+
 	buf.Reset()
 	l.formatOutput(buf, now, file, line, lvl)
 	if id != "" {
@@ -86,11 +101,11 @@ func (l *logger) Output(id string, lvl Level, calldepth int, s string) error {
 // -----------------------------------------
 
 func (l *logger) outputf(lvl Level, format string, v []interface{}) {
-	l.Output("", lvl, l.calldepth, fmt.Sprintf(format, v...))
+	l.Outputf("", lvl, l.calldepth, format, v...)
 }
 
 func (l *logger) output(lvl Level, v []interface{}) {
-	l.Output("", lvl, l.calldepth, fmt.Sprintln(v...))
+	l.Output("", lvl, l.calldepth, v...)
 }
 
 func (l *logger) Printf(format string, v ...interface{})   { l.outputf(Linfo, format, v) }
@@ -119,14 +134,12 @@ func (l *logger) Fatal(v ...interface{}) {
 func (l *logger) Panicf(format string, v ...interface{}) {
 	s := fmt.Sprintf(format, v...)
 	l.outputf(Lpanic, format, v)
-	// l.Output("", Lpanic, l.calldepth, s)
 	panic(s)
 }
 
 func (l *logger) Panic(v ...interface{}) {
 	s := fmt.Sprintln(v...)
 	l.output(Lpanic, v)
-	// l.Output("", Lpanic, l.calldepth, s)
 	panic(s)
 }