Close attach websocket connection on exec exit. Add pong handler.

[AndrienkoAleksandr]

Close attach websocket connection on exec exit. Add pong handler. Stop activity tracker on exec exit.

Referenced issue:

eclipse-che/che#16601

Signed-off-by: Oleksandr Andriienko [email protected]

[sleshchenko]

Already addressed

Does not WriteDataToWsConnections lead to deadlock since there are two locks set - in the method itself + in the called handler.removeConnection

// Write data to the all connections managed by handler.
func (handler *ConnectionHandlerImpl) WriteDataToWsConnections(data []byte) {
	defer handler.wsConnsLock.Unlock()
	handler.wsConnsLock.Lock()

	for _, wsConn := range handler.wsConns {
		if err := wsConn.WriteMessage(websocket.TextMessage, data); err != nil {
			if IsNormalWSError(err) {
				logrus.Errorf("failed to write to ws-conn message. Cause: %v", err)
			}
			handler.removeConnection(wsConn)
		}
	}
}

// Remove connection form handler.
func (handler *ConnectionHandlerImpl) removeConnection(wsConn *websocket.Conn) {
	defer handler.wsConnsLock.Unlock()
	handler.wsConnsLock.Lock()

	for index, wsConnElem := range handler.wsConns {
		if wsConnElem == wsConn {
			handler.wsConns = append(handler.wsConns[:index], handler.wsConns[index+1:]...)
		}
	}
}

An example I used to test

type TestArrayHandler struct {
	array     []int
	wsConnsLock *sync.Mutex
}

func main() {
	test := TestArrayHandler{
		array: []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10},
		wsConnsLock: &sync.Mutex{},
	}
	defer test.wsConnsLock.Unlock()
	test.wsConnsLock.Lock()
	removeFirst(&test)
}

func removeFirst(t *TestArrayHandler) {
	defer t.wsConnsLock.Unlock()
	t.wsConnsLock.Lock()

	t.array = append(t.array[:0], t.array[1:]...)
}

=>

fatal error: all goroutines are asleep - deadlock!

[sleshchenko]

WriteDataToWsConnections seems still has issue with deadlock, despite it's not really related to this PR I believe it's a critical part which must be addressed ASAP

[AndrienkoAleksandr]

I think deadlock fixed.

[sleshchenko]

Good job! 👍