Class WsRemoteEndpointImplServer

    • Method Detail

      • acquireMessagePartInProgressSemaphore

        protected boolean acquireMessagePartInProgressSemaphore​(byte opCode,
                                                                long timeoutExpiry)
                                                         throws java.lang.InterruptedException
        Acquire the semaphore that allows a message part to be written.

        The close message is a special case. It needs to be blocking else implementing the clean-up that follows the sending of the close message gets a lot more complicated. On the server, this creates additional complications as a dead-lock may occur in the following scenario:

        1. Application thread writes message using non-blocking
        2. Write does not complete (write logic holds message pending lock)
        3. Socket is added to poller (or equivalent) for write
        4. Client sends close message
        5. Container processes received close message and tries to send close message in response
        6. Container holds socket lock and is blocked waiting for message pending lock
        7. Poller fires write possible event for socket
        8. Container tries to process write possible event but is blocked waiting for socket lock
        9. Processing of the WebSocket connection is dead-locked until the original message write times out
        The purpose of this method is to break the above dead-lock. It does this by returning control of the processor to the socket wrapper and releasing the socket lock while waiting for the pending message write to complete. Normally, that would be a terrible idea as it creates the possibility that the processor is returned to the pool more than once under various error conditions. In this instance it is safe because these are upgrade processors (isUpgrade() returns true) and upgrade processors are never pooled.

        TODO: Despite the complications it creates, it would be worth exploring the possibility of processing a received close frame in a non-blocking manner.

        acquireMessagePartInProgressSemaphore in class WsRemoteEndpointImplBase
        opCode - The OPCODE for the message to be written
        timeoutExpiry - The time when the attempt to acquire the semaphore should expire
        true if the semaphore is obtained, otherwise false.
        java.lang.InterruptedException - If the wait for the semaphore is interrupted
      • updateStats

        protected void updateStats​(long payloadLength)
        Description copied from class: WsRemoteEndpointImplBase
        Hook for updating server side statistics. Called on every frame written (including when batching is enabled and the frames are buffered locally until the buffer is full or is flushed).
        updateStats in class WsRemoteEndpointImplBase
        payloadLength - Size of message payload
      • onWritePossible

        public void onWritePossible​(boolean useDispatch)
      • getTimeoutExpiry

        protected long getTimeoutExpiry()
      • onTimeout

        protected void onTimeout​(boolean useDispatch)