Alex Rudyy created QPID-8436:
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Summary: [Broker-J] [7.0.x] Improve performance of dequeuing old
queue entries on triggering ring policy
Key: QPID-8436
URL: https://issues.apache.org/jira/browse/QPID-8436
Project: Qpid
Issue Type: Improvement
Components: Broker-J
Reporter: Alex Rudyy
Fix For: qpid-java-broker-7.1.7
The performance of dequeuing old queue entries with triggering ring policy is
affected by the following factors:
* the oldest entry is not deleted immediately. As result, the deletion of the
same oldest entry can be requested from multiple publishing IO threads
* only one publishing thread can acquire the message with
{{QueueEntry#acquireOrSteal}}, whilst the rest of publishing IO threads would
set a {{DelayedAcquisitionStateListener}}. As result, thousands of
{{DelayedAcquisitionStateListeners}} can be potentially set on the same queue
entry
* Setting of {{DelayedAcquisitionStateListeners}} from concurrent IO threads
can consume host CPU up to 100% as there is a tight loop in
{{StateChangeListenerEntry#add(StateChangeListenerEntry<T,E>)}}. There is a
risk of running into defect {{QPID-8393}} whilst setting a listener.
* The old message is deleted in IO thread blocking the enqueing of new messages
It seems that high CPU consumption on setting of
{{DelayedAcquisitionStateListeners}} is the main contributor for the
perfromance degradation on old entries dequeueing by ring policy.
The current approach for dequeuing of old queue entries from ring policy should
be revisited. We need a mechanism to avoid multiple dequeueing of the same
queue entry from concurrent threads. Only after introduction of such mechanism
we can look into further performance optimisation for deletion of persistent
queue entries.
AutoCommitTransaction is used to dequeue entries on message expiration or
breaching ring policy threshold. As result, the dequeueing operation for
persistent queue entry blocks until queue entry record is removed from the
store and the underlying store transaction is synced to disk. The sequential
removal of multiple entries can results in unnecessary delays due to syncing
disk on every dequeue.
The broker performance for the corner cases described above can be
significantly improved by using asynchronous transactions in dequeue operations.
Asynchronous transaction does not wait for the store dequeue transaction to
sync to disk. As result, the performance of removal unneeded queue entries can
increase.
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