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From Justin Bertram <jbert...@apache.org>
Subject Re: Artemis 2.4.0 message loss in durability tests upon system power-off
Date Wed, 14 Feb 2018 14:57:45 GMT
The "messages added" metric for a queue is volatile so when the broker is
stopped it will be reset.  When the broker is started again the "messages
added" will be 0.  In your test you say the broker is "powered off" and
then you "resume" the broker.  What exactly does this mean?  It seems clear
that you aren't actually shutting down the broker otherwise the "messages
added" would be 0 when you started your consumers.  Please clarify.

Also, how do the broker's metrics compare with the producer's and
consumer's metrics?  I assume here that the producer and consumer are both
tracking the number of messages they produce/consume.

Also, do you have a way to reproduce this without a VM?


Justin

On Mon, Feb 5, 2018 at 7:11 PM, Anindya Haldar <anindya.haldar@oracle.com>
wrote:

> We are in the process of qualifying Artemis 2.4.0 for our stack. We ran
> some message durability related tests in the face of a power failure. The
> broker is running in a VirtualBox VM, and is set up in a system where disk
> caching is disabled. The VM runs OEL Linux 7, and the VirtualBox Manger
> itself is running under Windows 7 Enterprise.
>
>
>
> We use JMS API and persistent messaging. The transaction batch size in the
> producers is 1, and the message size for the tests in 1024 bytes. No
> consumers are running at this time, and we let the queues build up. Then
> the VirtualBox VM running the broker is 'powered off' (using VirtualBox
> facilities) 5 minutes along the way. The producers detect the broker's
> absence and stop.
>
>
>
> Then we resume the VM and the broker. The broker starts up and we get the
> queue stats from it before anything else:
>
>
>
> |NAME                     |ADDRESS                  |CONSUMER_COUNT
> |MESSAGE_COUNT |MESSAGES_ADDED |DELIVERING_COUNT |MESSAGES_ACKED |
> |testQueue1               |testQueue1               |0
> |106988        |106988         |0                |0              |
> |testQueue2               |testQueue2               |0
> |107077        |107077         |0                |0              |
> |testQueue3               |testQueue3               |0
> |106996        |106996         |0                |0              |
> |testQueue4               |testQueue4               |0
> |107076        |107076         |0                |0              |
>
>
>
> The total message count across the queues is 428137.
>
> Now we start the consumers (no producers this time). Finally when the
> consumers finish, we get the stats again. The consumers are claiming that
> they received and acknowledged 428126 messages, which is corroborated by
> the broker in the MESSAGES_ACKED column.
>
>
>
> |NAME                     |ADDRESS                  |CONSUMER_COUNT
> |MESSAGE_COUNT |MESSAGES_ADDED |DELIVERING_COUNT |MESSAGES_ACKED |
>
> |testQueue1               |testQueue1               |0              |0
>          |106988         |0                |106984         |
>
> |testQueue2               |testQueue2               |0              |0
>          |107077         |0                |107074         |
>
> |testQueue3               |testQueue3               |0              |0
>          |106996         |0                |106992         |
>
> |testQueue4               |testQueue4               |0              |0
>          |107076         |0                |107076         |
>
>
>
> You can clearly see some apparent anomalies:
>
> 1)      Post failure, and upon resumption, the broker said it had 428,137
> messages in the test queues, all combined (column MESSAGES_ADDED).
>
> 2)      When the consumers consumed it got 428,126 messages and
> acknowledged all of them. That is 11 short of 428,137.
>
> 3)      The broker, upon the consumers' completion reported 0 queue depth,
> but also said it got acknowledgements on 428,126 messages (column
> MESSAGES_ACKED).
>
>
>
> Questions:
>
> 1)      If we assume the 'MESSAGES_ADDED' column is accurate, then what
> happed to additional 11 messages that the consumers never received, and, as
> a result never acknowledged?
>
> 2)      If, according to the broker, the number of acknowledged messages
> is 11 less than the number of messages added to the queue, why did it
> declare the queues to be empty when 11 of the messages were not
> acknowledged?
>
> 3)      If we trust the 'MESSAGES_ADDED' stats as a baseline number then
> the system lost messages. And if we do not trust that statistic then what
> do we trust, and how do we know if it lost messages?
>
>
>
> The system ran into this issue 3 out of 4 times I ran the VM power failure
> test (with slightly different statistics, of course). We are very concerned
> that it is symptom of message loss in the system, and are also concerned
> about how to explain the anomalies. Will greatly appreciate any pointer
> that can help us understand and address the underlying issue here.
>
>
>
> Thanks,
>
> Anindya Haldar
>
> Oracle Marketing Cloud
>
>
>

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