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https://issues.apache.org/activemq/browse/AMQ-2803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=60311#action_60311
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Adrian Trenaman commented on AMQ-2803:
--------------------------------------
Cool. I'll see if I can put together a unit test for this - alternatively, get
in touch with me off-line and I can give you a non-Junit test-case.
> 'Zombie' messages created in KahaDB after failover, with warning 'Duplicate
> message add attempt rejected.'
> ----------------------------------------------------------------------------------------------------------
>
> Key: AMQ-2803
> URL: https://issues.apache.org/activemq/browse/AMQ-2803
> Project: ActiveMQ
> Issue Type: Bug
> Components: Message Store
> Affects Versions: 5.3.2
> Reporter: Adrian Trenaman
>
> Am doing some failover testing of ActiveMQ, sending 10,000 messages to the
> broker with a live consumer; the producer and consumer are transactional, and
> the broker is configured to use KahaDB. On failover of the broker, I see log
> warnings like this:
> {code}
> WARN | Duplicate message add attempt rejected. Message id:
> ID:Ade's-54024-1277715585703-0:29:1:1:240
> WARN | Duplicate message add attempt rejected. Message id:
> ID:Ade's-54024-1277715585703-0:24:1:1:241
> WARN | Duplicate message add attempt rejected. Message id:
> ID:Ade's-54024-1277715585703-0:23:1:1:242
> WARN | Duplicate message add attempt rejected. Message id:
> ID:Ade's-54024-1277715585703-0:0:1:1:237
> {code}
> When the test has run its course, I discover that there are no messages lost
> - all my messages have gone through successfully. However, I notice that
> there are in fact a number of 'zombie' messages on the queue: by 'zombie' I
> mean that the messages are in the store, and the JMX queueSize says they're
> there. However, if you browse the queue you don't see them, and, if you have
> a consumer on the queue, you won't receive them either.
> Looking into the code, in
> {{org.apache.activemq.store.kahadb.MessageDatabase}} you can see the
> following very interesting comments concerning the log warning:
> {code}
> // If the message ID as indexed, then the broker asked us to
> store a DUP
> // message. Bad BOY! Don't do it, and log a warning.
> LOG.warn("Duplicate message add attempt rejected. Message id:
> "+command.getMessageId());
> // TODO: consider just rolling back the tx.
> sd.messageIdIndex.put(tx, command.getMessageId(), previous);
> {code}
> So. It seems to me that while we're detecting the condition of the broker
> trying to reinsert a message that's already in the KahaDB correctly, we're
> not handling this case very well. The outcome is that while we do not get any
> message loss, we do get worrying warning messages *and* we get erroneous
> reporting of the queueSize in JMX which will mislead and create the
> perception of undelivered messages.
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