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https://issues.apache.org/jira/browse/QPIDJMS-552?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17434884#comment-17434884
]
ASF GitHub Bot commented on QPIDJMS-552:
----------------------------------------
franz1981 commented on a change in pull request #44:
URL: https://github.com/apache/qpid-jms/pull/44#discussion_r737530088
##########
File path: qpid-jms-client/src/main/java/org/apache/qpid/jms/JmsSession.java
##########
@@ -194,6 +193,42 @@ public void onPendingFailure(ProviderException cause) {
}
}
+ private void processCompletions() {
+ do {
+ if (!completionThread.compareAndSet(null, Thread.currentThread()))
{
+ return;
+ }
+ try {
+ Runnable completionTask;
+ while ((completionTask = completionTasks.poll()) != null) {
+ try {
+ completionTask.run();
+ } catch (Throwable t) {
+ LOG.debug("errored on processCompletions duty cycle",
t);
+ }
+ }
+ } finally {
+ completionThread.set(null);
+ }
+ } while (!completionTasks.isEmpty());
Review comment:
isEmpty can be called by *any* threads concurrently without
restrictions, but `poll` has to be called in a single threaded fashion ie one
thread "at time" or just the same thread
The use case of isEmpty is exactly for this type of duty cycle loop (very
common in Akka actors mailboxes, that use JCTools), which can be executed by
any thread, but serially, and is used to detect if it worth to "continue"
draining the mailbox.
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> JMS 2 Completion threads shouldn't scale with the number of sessions
> --------------------------------------------------------------------
>
> Key: QPIDJMS-552
> URL: https://issues.apache.org/jira/browse/QPIDJMS-552
> Project: Qpid JMS
> Issue Type: Bug
> Components: qpid-jms-client
> Affects Versions: 1.3.0
> Reporter: Francesco Nigro
> Priority: Major
>
> JMS 2 Completion threads are now tied to be one per JMS Session ie a client
> application with N JMS sessions need N completion threads to handle the
> completion events.
> Given that the asynchronous model of JMS 2 allows users to have few threads
> handling many JMS sessions, should be better to reduce the amount of
> completion threads without exceeding the number of available cores and
> shrink/grow according to the completion event processing load.
> If the user confine a connection in a thread handling many JMS sessions and
> the completion events are issued by the same Netty thread in sequence, if the
> completion processing for a JMS Session is fast enough, next JMS Sessions can
> reuse existing completion threads instead of using a new one.
> This model save using too many completion threads for users tasks that are
> supposed to be very fast: if the user task cause a specific JMS Session
> completion thread to block, the expectation is that the system should be able
> to create a new completion thread to handle other JMS Session completion
> events, as expected.
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