Race condition in read

[max8899]

Recently I'm trying to replace sockjs with gorilla/websocket in project kubernetes/dashboard, but there are some error happed, after some trobule shooting with go -race, there are some race condition details:

 ==================
 WARNING: DATA RACEWrite at 0x00c42023f002 by goroutine 100:
  internal/race.WriteRange()
      /usr/local/go/src/internal/race/race.go:49 +0x42
  syscall.Read()
      /usr/local/go/src/syscall/syscall_unix.go:165 +0x9a
  net.(*netFD).Read()
      /usr/local/go/src/net/fd_unix.go:246 +0x185
  net.(*conn).Read()
      /usr/local/go/src/net/net.go:181 +0x96
  net.(*TCPConn).Read()
      <autogenerated>:72 +0x72
  bufio.(*Reader).fill()
      /usr/local/go/src/bufio/bufio.go:97 +0x1a1
  bufio.(*Reader).Peek()
      /usr/local/go/src/bufio/bufio.go:129 +0x131
  dashboard/vendor/github.com/gorilla/websocket.(*Conn).read()
      /go/src/dashboard/vendor/github.com/gorilla/websocket/conn_read.go:12 +0x6d
  dashboard/vendor/github.com/gorilla/websocket.(*Conn).advanceFrame()
      /go/src/dashboard/vendor/github.com/gorilla/websocket/conn.go:778 +0x8f
  dashboard/vendor/github.com/gorilla/websocket.(*Conn).NextReader()
      /go/src/dashboard/vendor/github.com/gorilla/websocket/conn.go:938 +0x10c
  dashboard/vendor/github.com/gorilla/websocket.(*Conn).ReadMessage()
      /go/src/dashboard/vendor/github.com/gorilla/websocket/conn.go:1019 +0x3f
  dashboard/websocket.TerminalSession.Read()
      /go/src/dashboard/websocket/types.go:85 +0x120
  dashboard/websocket.(*TerminalSession).Read()
      <autogenerated>:2 +0xc7
  io.copyBuffer()
      /usr/local/go/src/io/io.go:390 +0x116
  io.Copy()
      /usr/local/go/src/io/io.go:360 +0x7e
  dashboard/vendor/k8s.io/client-go/tools/remotecommand.(*streamProtocolV2).copyStdin.func1()
      /go/src/dashboard/vendor/k8s.io/client-go/tools/remotecommand/v2.go:104 +0x159
krobelus-websocket_1  |
Previous read at 0x00c42023f002 by goroutine 87:
  runtime.slicecopy()
      /usr/local/go/src/runtime/slice.go:160 +0x0
  dashboard/vendor/github.com/gorilla/websocket.(*Conn).advanceFrame()
      /go/src/dashboard/vendor/github.com/gorilla/websocket/conn.go:849 +0xf9c
  dashboard/vendor/github.com/gorilla/websocket.(*Conn).NextReader()
      /go/src/dashboard/vendor/github.com/gorilla/websocket/conn.go:938 +0x10c
  dashboard/vendor/github.com/gorilla/websocket.(*Conn).ReadMessage()
      /go/src/dashboard/vendor/github.com/gorilla/websocket/conn.go:1019 +0x3f
  dashboard/websocket.TerminalSession.Read()
      /go/src/dashboard/websocket/types.go:85 +0x120
  dashboard/websocket.(*TerminalSession).Read()
      <autogenerated>:2 +0xc7
  io.copyBuffer()
      /usr/local/go/src/io/io.go:390 +0x116
  io.Copy()
      /usr/local/go/src/io/io.go:360 +0x7e
  dashboard/vendor/k8s.io/client-go/tools/remotecommand.(*streamProtocolV2).copyStdin.func1()
      /go/src/dashboard/vendor/k8s.io/client-go/tools/remotecommand/v2.go:104 +0x159
krobelus-websocket_1  |
Goroutine 100 (running) created at:
  dashboard/vendor/k8s.io/client-go/tools/remotecommand.(*streamProtocolV2).copyStdin()
      /go/src/dashboard/vendor/k8s.io/client-go/tools/remotecommand/v2.go:107 +0xc4
  dashboard/vendor/k8s.io/client-go/tools/remotecommand.(*streamProtocolV4).stream()
      /go/src/dashboard/vendor/k8s.io/client-go/tools/remotecommand/v4.go:65 +0x18c
  dashboard/vendor/k8s.io/client-go/tools/remotecommand.(*streamExecutor).Stream()
      /go/src/dashboard/vendor/k8s.io/client-go/tools/remotecommand/remotecommand.go:137 +0x42a
  dashboard/websocket.startProcess()
      /go/src/dashboard/websocket/handler.go:178 +0x6db
  dashboard/websocket.(*WSHandler).HandleTerminalSession()
      /go/src/dashboard/websocket/handler.go:124 +0x1403
  dashboard/websocket.(*WSHandler).HandleTerminalSession-fm()
      /go/src/dashboard/cmd/websocket.go:21 +0x5f
  net/http.HandlerFunc.ServeHTTP()
      /usr/local/go/src/net/http/server.go:1942 +0x51
  net/http.(*ServeMux).ServeHTTP()
      /usr/local/go/src/net/http/server.go:2238 +0xa2
  net/http.serverHandler.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2568 +0xbc
  net/http.(*conn).serve()
      /usr/local/go/src/net/http/server.go:1825 +0x71a
krobelus-websocket_1  |
Goroutine 87 (finished) created at:
  dashboard/vendor/k8s.io/client-go/tools/remotecommand.(*streamProtocolV2).copyStdin()
      /go/src/dashboard/vendor/k8s.io/client-go/tools/remotecommand/v2.go:107 +0xc4
  dashboard/vendor/k8s.io/client-go/tools/remotecommand.(*streamProtocolV4).stream()
      /go/src/dashboard/vendor/k8s.io/client-go/tools/remotecommand/v4.go:65 +0x18c
  dashboard/vendor/k8s.io/client-go/tools/remotecommand.(*streamExecutor).Stream()
      /go/src/dashboard/vendor/k8s.io/client-go/tools/remotecommand/remotecommand.go:137 +0x42a
  dashboard/websocket.startProcess()
      /go/src/dashboard/websocket/handler.go:178 +0x6db
  dashboard/websocket.(*WSHandler).HandleTerminalSession()
      /go/src/dashboard/websocket/handler.go:124 +0x1403
  dashboard/websocket.(*WSHandler).HandleTerminalSession-fm()
      /go/src/dashboard/cmd/websocket.go:21 +0x5f
  net/http.HandlerFunc.ServeHTTP()
      /usr/local/go/src/net/http/server.go:1942 +0x51
  net/http.(*ServeMux).ServeHTTP()
      /usr/local/go/src/net/http/server.go:2238 +0xa2
  net/http.serverHandler.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2568 +0xbc
  net/http.(*conn).serve()
      /usr/local/go/src/net/http/server.go:1825 +0x71a

The dashboard/websocket.(*TerminalSession).Read() is something like this, it almost the same as the code in dashboard:

func (t TerminalSession) Read(p []byte) (int, error) {
	mt, message, err := t.WSConn.ReadMessage()
	if err != nil {
		return 0, err
	}

	var msg TerminalMessage
	if err := json.Unmarshal([]byte(message), &msg); err != nil {
		return 0, err
	}

	switch msg.Op {
	case "stdin":
		return copy(p, msg.Data), nil
	case "resize":
		t.SizeChan <- remotecommand.TerminalSize{msg.Cols, msg.Rows}
		return 0, nil
	default:
		return 0, fmt.Errorf("unknown message type '%s'", msg.Op)
	}
}```

I try to add a mutex on ReadMessages, but it didn't work. Need some help on this .

[max8899]

ping @garyburd

[garyburd]

The application calls ReadMessage on a connection concurrently. Concurrent calls to read message are not supported.