ActiveMQ, AJAX and polling timeout value

[chago <na...@visualxs.com>]

I'm a bit confused by the line in _amq.js that initiates the long poll to the
server (Jetty 6.1.4 using continuations in my particular case.)

  _startPolling : function() {
    if (amq.poll)
      new Ajax.Request(amq.uri, { 
        method: 'get', 
        parameters: 'timeout=0', 
        onSuccess: amq._pollHandler });
  }

Tracing the code into MessageListenerServlet, it seems like this request
would cause an infinite wait to occur when continuation.suspend(timeout); is
reached. A timeout value of 0 implies an infinite wait.

I see the infinite wait when I run the Jetty 6.1.4 and ActiveMQ 5 SNAPSHOT
from my IDE, however when I run the activemq-web-demo module using maven,
the get request with a timeout of 0 returns immediately with an envelope
with no messages.

I'm confused by the different behaviors, and I can only debug into the code
that I launch from inside my IDE. I'm not sure how to remote debug from a
maven-launched app, but I will continue to look into this.

Any thoughts?

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Re: ActiveMQ, AJAX and polling timeout value

[chago <na...@visualxs.com>]

It appears that the difference lies in the fact that my maven config was
running version 6.1.4 of Jetty, while I was using version 6.1.5 in my IDE
debug session. When I downgraded to Jetty 6.1.4, the call made by the
_amq.js file returned immediately with an empty XML response.

With that said, I'm not sure which is the desired behavior. Perhaps GregW
can weigh in here. I'm not exactly sure why _amq.js is set up to invoke:

new Ajax.Request(amq.uri, {
        method: 'get',
        parameters: 'timeout=0',
        onSuccess: amq._pollHandler 
});

Why a hard-coded timeout=0? 

Jetty 6.1.5 treats continuation.suspend(0) as an indefinite suspend; at
least until there is a message to send. For some reason in Jetty 6.1.4,
continuation.suspend(0) resumes immediately.

Any light that can be shed on the 'timeout=0' and the differences in how
Jetty handles it would be appreciated.
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