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From "Rui Gu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (AMQ-3447) When MessageListenerServlet is running under servlet3, the continuation is not timing out.
Date Thu, 11 Aug 2011 15:23:27 GMT
When MessageListenerServlet is running under servlet3, the continuation is not timing out.
------------------------------------------------------------------------------------------

                 Key: AMQ-3447
                 URL: https://issues.apache.org/jira/browse/AMQ-3447
             Project: ActiveMQ
          Issue Type: Bug
    Affects Versions: 5.5.0
         Environment: Ubuntu 11.04 using glassfish as web container running servlet 3.0 webapp.
            Reporter: Rui Gu


In MessageListenerServlet.java

          if (message == null && client.getListener().getUndeliveredMessages().size()
== 0) {
                Continuation continuation = ContinuationSupport.getContinuation(request);
                
                if (continuation.isExpired()) {
                    response.setStatus(HttpServletResponse.SC_OK);
                    StringWriter swriter = new StringWriter();
                    PrintWriter writer = new PrintWriter(swriter);
                    writer.println("<ajax-response>");
                    writer.print("</ajax-response>");

                    writer.flush();
                    String m = swriter.toString();
                    response.getWriter().println(m); 
                    
                    return;
                }

                continuation.setTimeout(timeout);
                continuation.suspend();
                LOG.debug( "Suspending continuation " + continuation );
                
                // Fetch the listeners
                AjaxListener listener = client.getListener();
                listener.access();

                // register this continuation with our listener.
                listener.setContinuation(continuation);
                
                return;
            }

Based on above code, the continuation is expected to be expired after given timeout when there
is no message available for the ajax client and the ajax client will then receive an "empty"
message. However based on the servlet 3 Continuation implementation in jetty (Servlet3Continuation.java)
the only place where the continuation is set to expire is within the below method (there is
a bug in this method as well). 

public void addContinuationListener(final ContinuationListener listener)
    {
        AsyncListener wrapped = new AsyncListener()
        {
            public void onComplete(final AsyncEvent event) throws IOException
            {
                listener.onComplete(Servlet3Continuation.this);
            }

            public void onError(AsyncEvent event) throws IOException
            {
                listener.onComplete(Servlet3Continuation.this);
            }

            public void onStartAsync(AsyncEvent event) throws IOException
            {
                event.getAsyncContext().addListener(this);
            }

            public void onTimeout(AsyncEvent event) throws IOException
            {
                _expired=true;
                listener.onTimeout(Servlet3Continuation.this);
            }
        };
        
        if (_context==null)
            _context.addListener(wrapped);
        else
            _listeners.add(wrapped);
    }

Without adding a listener the continuation will never be set to expire, therefore the "empty"
response is never sent back to the client, the connection from the client is resumed and suspended
over and over again until the connection is aborted by client or there is a message available.

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