Nevin Chen created AMQ-6059:
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Summary: 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
*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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