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From "Colin MacNaughton (JIRA)" <j...@apache.org>
Subject [jira] Created: (AMQ-2413) Hangs possible because of Queue.doPageIn
Date Fri, 25 Sep 2009 01:27:51 GMT
Hangs possible because of Queue.doPageIn
----------------------------------------

                 Key: AMQ-2413
                 URL: https://issues.apache.org/activemq/browse/AMQ-2413
             Project: ActiveMQ
          Issue Type: Bug
          Components: Broker
    Affects Versions: 5.4.0
         Environment: 5.4 branch 818147. Some changes after this hide this error, but I'm
still concerned it might be a problem.
            Reporter: Colin MacNaughton
            Priority: Critical


I don't understand the intent of the following code in Queue.doPageIn() and in rev 818147
it was causing delivery to the consumer to get hung (temporarily until message expiration
check kickstarts it again). See the commented out lines of code that determine how many messages
to attempt to page in. 

{code}
    private List<QueueMessageReference> doPageIn(boolean force) throws Exception {
        List<QueueMessageReference> result = null;
        List<QueueMessageReference> resultList = null;
        synchronized(dispatchMutex) {
            //WHAT IS THIS DOING?
            //int toPageIn = getMaxPageSize() + Math.max(0, (int)destinationStatistics.getInflight().getCount())
-pagedInMessages.size();

            //DOES THIS MAKE MORE SENSE:
            int toPageIn = Math.min(getMaxPageSize(), messages.size());
            
            if (LOG.isDebugEnabled()) {
                LOG.debug(destination.getPhysicalName() + " toPageIn: "  + toPageIn + ", Inflight:
"
                        + destinationStatistics.getInflight().getCount()
                        + ", pagedInMessages.size " + pagedInMessages.size());
            }
            
            //WHAT IS THIS DOING?
            //toPageIn = Math.max(0, Math.min(toPageIn, getMaxPageSize()));
                       
            if (isLazyDispatch()&& !force) {
                // Only page in the minimum number of messages which can be dispatched immediately.
                toPageIn = Math.min(getConsumerMessageCountBeforeFull(), toPageIn);
            }
   
{code}

It is definitely possible that I'm just not understanding the intent of the code, but whatever
it is, it's not working, and consequently I'm not sure that the subsequent fixes on the branch
have eliminated the problem. The attached patch contains both a unit test, that tests several
combinations of ack mode, vm cursoring, and delivery mode, as well as version of Queue which
should be applied against revirion 818147 -- this version has the fix commented out and preserves
the buggy behavior

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