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From "Nevin Chen (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (AMQ-6059) DLQ message lost after broker restarts
Date Tue, 24 Nov 2015 02:05:11 GMT

     [ https://issues.apache.org/jira/browse/AMQ-6059?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Nevin Chen updated AMQ-6059:
----------------------------
    Attachment: LevelDBStoreRecoveryBrokerTest.java

Test case to reproduce this issue. It is expected to run in activemq-unit-tests project.

> DLQ message lost after broker restarts
> --------------------------------------
>
>                 Key: AMQ-6059
>                 URL: https://issues.apache.org/jira/browse/AMQ-6059
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 5.12.1
>         Environment: Windows, Linux Redhat
>            Reporter: Nevin Chen
>         Attachments: LevelDBStoreRecoveryBrokerTest.java, activemq.xml
>
>
> *How to Reproduce*
> 1. Default ActiveMQ 5.12.1 package with the attached activemq.xml.
> 2. Send a message to a queue with expiration time one second.
> 4. After the expiry time, the message will be moved to DLQ. This can be monitored by
the AMQ web console.
> 5. Restart AMQ. You will find that the message disappear from the AMQ web console. Try
to consume the message from the DLQ, nothing is received.
> *Cause Analysis*
> 1. KahaDB works well. It means the cause should be related to the leveldb mechanism.
> 2. In my understanding, the JMS message is persistent to a log file and leveldb will
maintain to a reference to the position where the JMS message is stored in the log. After
a message expires, AMQ will copy the expired JMS message and the reference to the posistion
is also copied, then send to DLQ. When AMQ restarts, DLQ will recover the message from the
persistent storage. Since the DLQ message shares the same reference to the JMS message data,
the message in DLQ also has the expiration time that is the same as the original message.
The expiry scanner will detect the DLQ message expires and remove it. That's why the message
is lost after restart.
> 3. Actually, the message to DLQ is not completely the same as the origial message. Because
the expiration time will be reset to 0 and some more message properties will be added. The
DLQ message should not reuse the same reference to message data. For more details, please
refer to org.apache.activemq.broker.region.RegionBroker.sendToDeadLetterQueue(ConnectionContext
context, MessageReference node, Subscription subscription, Throwable poisonCause) method.
> *Fixed Proposal*
> In org.apache.activemq.broker.region.RegionBroker.sendToDeadLetterQueue(ConnectionContext
context, MessageReference node, Subscription subscription, Throwable poisonCause) method,
after the message is copied, set the dataLocator to null (message.getMessageId().setDataLocator(null)
to force leveldb to save the new JMS message data and refer to a new position.



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