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From "Gabriel Gerhardsson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AMQ-4022) SEND directly after SUBSCRIBE causes bad state -> no DISCONNECT receipt
Date Tue, 11 Sep 2012 13:07:07 GMT

    [ https://issues.apache.org/jira/browse/AMQ-4022?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13452989#comment-13452989
] 

Gabriel Gerhardsson commented on AMQ-4022:
------------------------------------------

Thanks for the reply Timothy. 

We haven't tried with 5.6 or 5.7 for this issue, no. But, I have good news: I think I just
found the problem and am currently testing a fix. 

I found that the problem is a deadlock in broker.TransportConnection. Once that was clear,
the fix was rather easy. I'm currently running the test script and am hopeful that there'll
be no problems. If everything's ok I'll get back to you with a patch. 

I checked the 5.6 branch and can confirm that the issue does exist there also. Haven't checked
5.7.
                
> SEND directly after SUBSCRIBE causes bad state -> no DISCONNECT receipt
> -----------------------------------------------------------------------
>
>                 Key: AMQ-4022
>                 URL: https://issues.apache.org/jira/browse/AMQ-4022
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: stomp
>    Affects Versions: 5.5.1
>         Environment: SLES11-SP1 x86_64
>            Reporter: Gabriel Gerhardsson
>         Attachments: amqtest.pl, Net_Stomp.pm.diff
>
>
> Executive summary
> ---
> A message is lost, the connection ends up in a strange state, and then when the client
sends DISCONNECT it gets no receipt.
> Details
> ---
> Steps to reproduce:
> 1) Using STOMP
> 2) Send a SUBSCRIBE message with destination=/topic/foo, without asking for a receipt.
No other options sent in message.
> 3) Send a message to /topic/foo, without asking for a receipt.
> 4) Wait 10ms for message
> 5) Go right ahead and send DISCONNECT message, asking for a receipt.
> 5.1) About 20% of the time, no DISCONNECT receipt is received, however long the client
waits. This seems to coincide with the case when the message doesn't arrive in #4.
> 5.2) It does look like ActiveMQ gets the DISCONNECT message tho since it unsubscribes
the client from /topic/foo at that timestamp.
> The DISCONNECT receipt getting lost is clearly a bug. Waiting for the receipt is important
since I've seen cases where the client isn't unregistered properly in ActiveMQ if the client
just sends DISCONNECT and then closes the socket.
> Test script
> ---
> Apply the small patch to the perl library Net/Stomp.pm
> It's a naive minimal patch to make it wait for a receipt for the DISCONNECT message.
It will actually just wait for any frame to arrive and won't check what it is, but it's enough
for this test.
> Run amqtest.pl a few times. A non-buggy run completes almost immediately. A buggy run
hangs the script during disconnect.
> Workaround
> ---
> -When sending the SUBSCRIBE with receipt requested, and waiting for the receipt before
sending the SEND, I was unable to reproduce the issue, even after running the script 100000
times.-
> No, it turns out that the workaround suggested above does not completely eliminate the
problem. It probably just introduces a large enough delay to almost always avoid the race
condition. After 30000 additional test runs with the script the error occured again.

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