httpservletmessenger.java

JXTA&#8482 is a set of open, generalized peer-to-peer (P2P) protocols that allow any networked devi

    @Override
    public boolean isIdleImpl() {
        // We do not use self destruction.
        return false;
    }
    
    /**
     * Send messages. Messages are queued and processed by a thread
     * running HttpClientConnection.
     */
    @Override
    public synchronized void sendMessageBImpl(Message message, String service, String serviceParam) throws IOException {
        
        if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
            LOG.fine("Send " + message + " to " + dstAddress.toString() + "\n\t" + toString());
        }
        
        if (isClosed()) {
            IOException failure = new IOException("Messenger was closed, it cannot be used to send messages.");
            
            if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
                LOG.log(Level.FINE, failure.getMessage(), failure);
            }
            
            throw failure;
        }
        
        // Set the message with the appropriate src and dest address
        message.replaceMessageElement(EndpointServiceImpl.MESSAGE_SOURCE_NS, srcAddressElement);
        
        EndpointAddress destAddressToUse = getDestAddressToUse(service, serviceParam);
        
        MessageElement dstAddressElement = new StringMessageElement(EndpointServiceImpl.MESSAGE_DESTINATION_NAME,
                destAddressToUse.toString(), null);
        
        message.replaceMessageElement(EndpointServiceImpl.MESSAGE_DESTINATION_NS, dstAddressElement);
        
        // doSend returns false only when this messenger is closed.
        if (!doSend(message)) {
            // send message failed
            IOException failure = new IOException("Messenger was closed, it cannot be used to send messages.");
            
            if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
                LOG.log(Level.FINE, "sendMessage failed (messenger closed).\n\t" + toString(), failure);
            }
            
            throw failure;
        }
        
        if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
            LOG.fine("sendMessage successful for " + message + "\n\t" + toString());
        }
    }
    
    // Must be called from synchronized context only.
    private boolean doSend(Message message) {
        
        // No need to wait for the messenger to be free. Transport
        // messengers have no obligation to behave nicely if they're
        // used by mltiple threads. If a thread comes here while
        // we're already busy sending, then that's a congestion. Just
        // drop the new message (pretend it went out).
        // This is not even so nasty, because jetty has a sizeable
        // output buffer. As long as that buffer is not full, sending
        // is instantaneou. If sending starts blocking, then we can honestly
        // drop messages.
        
        if (isClosed()) {
            return false;
        }
        
        long now = TimeUtils.timeNow();
        
        if (sendResult != SEND_IDLE) {
            // check if that connection is a lemon
            if ((sendResult == SEND_TOOLONG) && (now > (sendingSince + MAX_SENDING_BLOCK))) {
                close();
            }
            return true;
        }
        
        // put the message on the outgoing "queue" of size 1
        outgoingMessage = message;
        sendResult = SEND_INPROGRESS;
        sendingSince = now;
        
        if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
            LOG.fine("Queued " + message);
        }
        
        // notify the servlet if it was waiting for a message
        notifyAll();
        
        // wait for the result of the send Since there is ample
        // buffering underneath, we're not supposed to wait for long;
        // unless we outdo the connection, in which case, we might as
        // well start dropping. No point in blocking.
        // FIXME: [e-mail] - this is a rudimentary fix. We need
        // something like watchedOutputStream instead. Being forced
        // to do a two-way handshake with a servlet thread is pretty
        // ridiculous too. We need a simpler http transport.
        
        long absoluteTimeOut = TimeUtils.toAbsoluteTimeMillis(MAX_SENDING_WAIT);
        
        while (!isClosed()) {
            if (sendResult != SEND_INPROGRESS) {
                break;
            }
            
            long waitfor = TimeUtils.toRelativeTimeMillis(absoluteTimeOut);
            
            if (waitfor <= 0) {
                break;
            }
            
            try {
                wait(waitfor);
            } catch (InterruptedException e) {
                Thread.interrupted();
                if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
                    LOG.log(Level.FINE, "InterruptedException timeout = " + MAX_SENDING_WAIT + "\n\t" + toString(), e);
                }
                break;
            }
        }
        
        if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
            LOG.fine("Got result\n\t" + toString());
        }
        
        if (isClosed() && (SEND_INPROGRESS == sendResult)) {
            return false;
        }
        
        // If the operation completed just confirm that we're done
        // reading the result too. Else mark that we don't care.
        // When it completes the result will be discarded. By default,
        // the we return ok. If the operation did not complete fast
        // enough, that's what we return.
        
        boolean result = (sendResult != SEND_FAIL);
        
        if (sendResult == SEND_INPROGRESS) {
            sendResult = SEND_TOOLONG;
            outgoingMessage = null;
        } else {
            sendResult = SEND_IDLE;
        }
        
        // Let another contending thread use this messenger.
        notifyAll();
        
        return result;
    }
    
    /**
     *  Retrieve a message from the "queue" of messages for the servlet.
     *
     *  @param timeout Number of milliseconds to wait for a message. Per Java
     *  convention 0 (zero) means wait forever.
     *  @return the message or <code>null</code> if no message was available
     *  before the timeout was reached.
     *  @throws InterruptedException If the thread is interrupted while waiting.
     */
    protected synchronized Message waitForMessage(long timeout) throws InterruptedException {
        if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
            LOG.fine("Waiting (" + (0 == timeout ? "forever" : Long.toString(timeout)) + ") for message\n\t" + toString());
        }
        
        if (0 == timeout) {
            // it's forever
            timeout = Long.MAX_VALUE;
        }
        
        long absoluteTimeOut = TimeUtils.toAbsoluteTimeMillis(timeout);
        
        while (!isClosed() && (null == outgoingMessage)) {
            long waitfor = TimeUtils.toRelativeTimeMillis(absoluteTimeOut);
            
            if (waitfor <= 0) {
                break;
            }
            
            wait(waitfor);
        }
        
        // get the message
        Message result = outgoingMessage;
        
        outgoingMessage = null; // Msg can only be picked-up once.
        
        if (!isClosed() && (result == null)) {
            // ABSURD, but seems to happen: the message sent was NULL
            // and the sender thread is waiting for the completion event.
            // There would be no such thing, but we can make sure it stops
            // waiting and still leave the messenger in a sane state if there
            // was no such absurdity going on.
            
            sendResult = SEND_IDLE;
            notifyAll();
        }
        
        if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
            LOG.fine("Returning " + result + "\n\t" + toString());
        }
        
        return result;
    }
    
    protected synchronized void messageSent(boolean wasSuccessful) {
        if (Logging.SHOW_FINE && LOG.isLoggable(Level.FINE)) {
            LOG.fine("messageSent(" + wasSuccessful + ")\n\t" + toString());
        }
        
        if (SEND_TOOLONG == sendResult) {
            // No-one cares for the result any more. Let the next send go.
            sendResult = SEND_IDLE;
        } else {
            sendResult = wasSuccessful ? SEND_SUCCESS : SEND_FAIL;
        }
        
        notifyAll();
    }
    
    /**
     * {@inheritDoc}
     *
     *  <p/>An implementation for debugging. Do not depend on the format.
     */
    @Override
    public String toString() {
        return "[" + super.toString() + "] isClosed=" + isClosed() + " sendResult=" + sendResult + " outmsg=" + outgoingMessage;
    }
}