Christopher L. Shannon created AMQ-9698:
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Summary: Fix durable message expiration
Key: AMQ-9698
URL: https://issues.apache.org/jira/browse/AMQ-9698
Project: ActiveMQ Classic
Issue Type: Bug
Reporter: Christopher L. Shannon
Assignee: Christopher L. Shannon
Fix For: 6.2.0, 5.19.1, 6.1.7
There are several bugs related the broker handling expiration of messages on
Durable topic subscriptions, both when the client expires and also the broker
expires. The bugs are related specifically to durables in both the expiration
thread and the pending message cursor and don't apply to Topic subs (topic subs
don't keep references after dispatch and there's no store to ack).
The following issues exist:
# *Skipping client expired acks:* If a client expires a message and sends back
an expiration ack, the broker marks the message reference as expired. This
means if multiple durable subs try and expire the same message and are using
the same reference (this can happen when using caching in PendingMessageCursor)
the first one will ack and the rest of the messages never get acked in the
store. Furthermore, memory usage tracking is impacted as the counter isn't
decremented.
# *Memory tracking by the cursor:* AbstractStoreCursor does not decrement the
usage counter on the message reference if removed using the
cursor.remove(message) method. This causes the usage tracker to not decrement
even after removal in some cases.
# *Expiry thread:* The topic expiration thread has multiple problems.
#* The thread is inefficient. It uses the browse method and just loads messages
into the browse map even if there are no offline durables and iterates over
every subscription.
#* The thread will just expire the message on any offline durable or any
durable that is marked to expire if online without taking into account whether
the durable has already acked the message. This can lead to lots of warnings in
the logs for unmatched acks if acking multiple times (which could happen if
there was another online sub preventing the entire removal of the message)
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