Merge pull request #404 from 1978629634/fsync-freelock

Do not acquire lock for file.Sync() fsync call

Author: k8s-ci-robot

klog.go

@@ -1011,7 +1011,8 @@ func (l *loggingT) exit(err error) {
 logExitFunc(err)
 return
 }
-l.flushAll()
+files := l.flushAll()
+l.syncAll(files)
 OsExit(2)
 }
 
@@ -1223,24 +1224,38 @@ func StartFlushDaemon(interval time.Duration) {
 // lockAndFlushAll is like flushAll but locks l.mu first.
 func (l *loggingT) lockAndFlushAll() {
 l.mu.Lock()
-l.flushAll()
+files := l.flushAll()
 l.mu.Unlock()
+// Some environments are slow when syncing and holding the lock might cause contention.
+l.syncAll(files)
 }
 
-// flushAll flushes all the logs and attempts to "sync" their data to disk.
+// flushAll flushes all the logs
 // l.mu is held.
-func (l *loggingT) flushAll() {
+func (l *loggingT) flushAll() []flushSyncWriter {
+files := make([]flushSyncWriter, 0, severity.NumSeverity)
 // Flush from fatal down, in case there's trouble flushing.
 for s := severity.FatalLog; s >= severity.InfoLog; s-- {
 file := l.file[s]
 if file != nil {
 _ = file.Flush() // ignore error
-_ = file.Sync() // ignore error
 }
+files = append(files, file)
 }
 if logging.loggerOptions.flush != nil {
 logging.loggerOptions.flush()
 }
+return files
+}
+
+// syncAll attempts to "sync" their data to disk.
+func (l *loggingT) syncAll(files []flushSyncWriter) {
+// Flush from fatal down, in case there's trouble flushing.
+for _, file := range files {
+if file != nil {
+_ = file.Sync() // ignore error
+}
+}
 }
 
 // CopyStandardLogTo arranges for messages written to the Go "log" package's

klog_test.go

@@ -546,7 +546,8 @@ func TestOpenAppendOnStart(t *testing.T) {
 }
 
 // ensure we wrote what we expected
-logging.flushAll()
+files := logging.flushAll()
+logging.syncAll(files)
 b, err := ioutil.ReadFile(logging.logFile)
 if err != nil {
 t.Fatalf("unexpected error: %v", err)
@@ -817,7 +818,8 @@ func BenchmarkLogs(b *testing.B) {
 Warning("warning")
 Info("info")
 }
-logging.flushAll()
+files := logging.flushAll()
+logging.syncAll(files)
 }
 
 // Test the logic on checking log size limitation.