binarylog: Use a simple boolean rather than a sync.Once (#4581)

internal/binarylog/sink.go

@@ -86,21 +86,24 @@ func (ws *writerSink) Write(e *pb.GrpcLogEntry) error {
 func (ws *writerSink) Close() error { return nil }
 
 type bufferedSink struct {
- mu sync.Mutex
- closer io.Closer
- out Sink // out is built on buf.
- buf *bufio.Writer // buf is kept for flush.
-
- writeStartOnce sync.Once
- writeTicker  *time.Ticker
- done  chan struct{}
+ mu  sync.Mutex
+ closer  io.Closer
+ out  Sink // out is built on buf.
+ buf  *bufio.Writer // buf is kept for flush.
+ flusherStarted bool
+
+ writeTicker *time.Ticker
+ done chan struct{}
 }
 
 func (fs *bufferedSink) Write(e *pb.GrpcLogEntry) error {
- // Start the write loop when Write is called.
- fs.writeStartOnce.Do(fs.startFlushGoroutine)
  fs.mu.Lock()
  defer fs.mu.Unlock()
+ if !fs.flusherStarted {
+ // Start the write loop when Write is called.
+ fs.startFlushGoroutine()
+ fs.flusherStarted = true
+ }
  if err := fs.out.Write(e); err != nil {
  return err
  }