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From "Alex Rudyy (Jira)" <j...@apache.org>
Subject [jira] [Created] (QPID-8436) [Broker-J] [7.0.x] Improve performance of dequeuing old queue entries on triggering ring policy
Date Fri, 03 Apr 2020 11:45:00 GMT
Alex Rudyy created QPID-8436:

             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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