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https://issues.apache.org/jira/browse/AMQ-9813?focusedWorklogId=994061&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-994061
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ASF GitHub Bot logged work on AMQ-9813:
---------------------------------------
Author: ASF GitHub Bot
Created on: 01/Dec/25 14:17
Start Date: 01/Dec/25 14:17
Worklog Time Spent: 10m
Work Description: cshannon commented on PR #1551:
URL: https://github.com/apache/activemq/pull/1551#issuecomment-3596784873
After looking more into this I think it's fine to merge. It's only a single
message being added and the memory pressure should not be so high that one
message causes an OOM. There are plenty of spots in the broker where we are
incrementing/decrementing memory counters and it isn't exact because messages
are still in memory and being processed. In fact, queues allow paging in up to
110% of the memory setting to allow dispatch and unblocking. The memory usage
tracking is always just an estimate in general and I think the fix makes sense
and unlikely to cause any issues.
Issue Time Tracking
-------------------
Worklog Id: (was: 994061)
Time Spent: 50m (was: 40m)
> Incorrect QueueSize if Non-Persistent messages with TTL is used
> ---------------------------------------------------------------
>
> Key: AMQ-9813
> URL: https://issues.apache.org/jira/browse/AMQ-9813
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker
> Affects Versions: 6.2.0, 5.19.1
> Reporter: Radek Kraus
> Assignee: Christopher L. Shannon
> Priority: Major
> Fix For: 6.1.9, 5.19.2, 6.2.1
>
> Time Spent: 50m
> Remaining Estimate: 0h
>
> Sometimes, I detect a problem with incorrect QueueSize, when non-persitent
> messages with TTL is used.
> *UseCase/Symptoms*
> * produce/consume non-persistent messages with defined TTL (expiration)
> * producerFlowControl=false
> * consumers "are slow", it means that some messages are expired (broker side
> or client side)
> * QueueSize sometimes reports non-zero value even when all messages are
> consumed/expired
> * Broker does not "push" next messages to consumers
> ** JMX method {{browseAsTable()}} does not provide messages
> ** JMX method {{purge()}} does not remove messages (QueueSize is still
> non-zero, nothing is deleted)
> * It seems like messages are expired, but QueueSize still reports non-zero
> values
> * after Broker restart QueueSize is reset to zero (expected for
> non-persitent messages)
> *Analyse*
> * I guess, that problem was introduced by AMQ-5785 (by
> [8b23e07|https://github.com/apache/activemq/commit/8b23e07], where deadlock
> was solved)
> * there is a valid AMQ-5785 comment without next reaction
> * what happens in
> [8b23e07|https://github.com/apache/activemq/commit/8b23e07] commit (nearly
> the same what is written in [AMQ-5785
> comment|https://issues.apache.org/jira/browse/AMQ-5785?focusedCommentId=15607861&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15607861]):
> ** contract of {{expireOldMessages()}} method was changed to don't invoke
> {{discardExpiredMessage(MessageReference)}} (which is finally responsible to
> "process expired message")
> ** the invocation of {{discardExpiredMessage(MessageReference)}} was moved
> out of synchronized section (deadlock prevention), see
> {{onUsageChanged(Usage, int, int)}} method
> ** but the *problem is that {{expireOldMessages()}} method is invoked from
> next methods* ({{{}tryAddMessageLast(MessageReference, long){}}},
> {{{}addMessageFirst(MessageReference){}}}), where
> *{{discardExpiredMessage(MessageReference)}} method is no longer invoked*
> (after change), *what it is problem from my point of view*
> * IMHO "message expiration process" can be invoked:
> ** from {{onUsageChanged(Usage, int, int)}} method ({{{}UsageListener{}}}),
> asynchronously triggered by Usage.setPercentUsage(int) (thread pool executor)
> ** or "directly" from {{tryAddMessageLast(MessageReference, long)}} (in case
> when {{OrderedPendingList}} is used)
> ** it depends on situations (timings), which method is invoked "at first"
> ** when {{tryAddMessageLast(MessageReference, long)}} method is invoked,
> then expired messages are only removed from {{{}memoryList{}}}, but
> {{discardExpiredMessage(MessageReference)}} is never invoked (what it is the
> problem)
> *PR* (https://github.com/apache/activemq/pull/1551)
> * I added "missing" invocation of
> {{discardExpiredMessage(MessageReference)}} method into
> {{{}tryAddMessageLast(MessageReference, long){}}},
> {{addMessageFirst(MessageReference)}} methods
> * I tried to use same "postponed" strategy (outside of synchronization) like
> was already done in original commit (see {{{}onUsageChanged(Usage, int,
> int){}}}) method
> * I tried to write JUnit test, but it is complicated, because it depends on
> timings (from my expiriences TTL must be very small to simulate the problem,
> see {{{}FullDestinationMemoryMessageExpirationTest{}}})
> Could you please check/analyze my findings?
> In each case (IMHO)
> [8b23e07|https://github.com/apache/activemq/commit/8b23e07] breaks previous
> contract of {{expireOldMessages()}} methods, which can caused that expired
> messages are not "processed", when expiration is triggered by
> {{{}tryAddMessageLast(MessageReference, long){}}},
> {{addMessageFirst(MessageReference)}} methods.
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