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From Matt Broadstone <mbroa...@gmail.com>
Subject Re: acknowledge not releasing message with C++ messaging api
Date Wed, 29 Apr 2015 19:03:36 GMT
On Wed, Apr 29, 2015 at 3:01 PM, Matt Broadstone <mbroadst@gmail.com> wrote:

> On Wed, Apr 29, 2015 at 2:55 PM, Gordon Sim <gsim@redhat.com> wrote:
>> On 04/29/2015 05:46 PM, Matt Broadstone wrote:
>>> Hi,
>>> I have a service using the C++ Messaging API which connects to a single
>>> instance of qpidd (currently on the same machine), which seems to crash
>>> out
>>> with this exception every couple of days under moderate load:
>>> qpidd[68257]: 2015-04-28 11:56:38 [Broker] error
>>> qpid. resource-limit-exceeded:
>>> Maximum depth exceeded on
>>> b1386bee-a36c-449d-953f-c25f4842e76d_hive.guest.metadata_7bf9355b-524b-4853-89bd-1848366cd21f:
>>> current=[count: 389438, size: 104857546], max=[size: 104857600]
>>> (/build/buildd/qpid-cpp-0.28/src/qpid/broker/Queue.cpp:1575)
>>> Using qpid-stat I don't see the queue depth ever increase from 0 (which I
>>> gather is why the exception is thrown, from reading the code), however I
>>> -do- notice that the "acquired" count is increasing with every message
>>> with
>>> no corresponding "release" (release count is always 0).
>> That's actually 'expected', in terms of the code. It only increments the
>> released count when a messages is released back to the queue, rather than
>> being acknowledged and dequeued. Also there is nothing at present that
>> decrements the acquired count, so it would be expected to keep going up.
> Okay, good to know, just making sure I wasn't seeing a huge problem with
> improperly handled messages here.
>> The exception above is indeed a result of the queue backing up,
>> apparently reaching a depth of 389438 messages. What address options if any
>> are used for the receiver consuming from that queue? Is there anything to
>> indicate whether that receiver was behaving normally just before the point
>> at which the error occurred?
> I'm using no address options at all. The two programs I submitted earlier
> (mqget/mqsend) are reduced examples of what we're using (except the
> receiver in my case uses the "multiple receivers" Session.getNext().fetch()
> etc). Aside from that it's very "vanilla" right now. AFAICT everything was
> fine, until it wasn't. The original bug occurred with version 0.28, so
> maybe there's an issue with the fact that it was still using the legacy
> store? However, everything I see here indicates nothing ever touched the
> disk (these are just messages being published to a topic). As for the
> receiving side, each receiver (and this one in particular) are set to a
> prefetch(capacity) of 10.
> What seems particularly strange to me is that the backup is for hundreds
> of thousands of messages, how could that even be possible? Right now we
> have about 10 producers publishing every ~6 seconds.
> Matt

Also, what is the recommended failover scenario for this situation?
Basically what happened for us is that this "situation" occurred, and then
were no longer receiving ANY messages on that receiver and it took our
whole system down. The "workaround" was to simply restart the qpidd process.


>>> My service currently looks a lot like the "Receiving Messages from
>>> Multiple
>>> Sources" on this page:
>>> https://qpid.apache.org/releases/qpid-0.28/messaging-api/cpp/api/index.html
>>> ,
>>> and I am definitely calling the message agnostic "session.acknowledge()"
>>> in
>>> my main event loop, so I'm not sure why the messages are never released
>>> (presuming that messages would be released about
>>> settling/acknowledgement).
>>> I've created a ticket for what I think is a bug in the broker here:
>>> https://issues.apache.org/jira/browse/QPID-6517, but figured I would
>>> post
>>> here as well
>> Always a good idea, just to make sure it gets noticed!
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