[jboss-jira] [JBoss JIRA] (DROOLS-3412) Performance degradation with session pools

[Christian Liebhardt (Jira)]

    [ https://issues.jboss.org/browse/DROOLS-3412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13671188#comment-13671188 ] 

Christian Liebhardt commented on DROOLS-3412:
---------------------------------------------

The slow down seems to be caused by increased GC activity. This grap shows the GC behavior of two runs, the frequency in which sessions are created should have been constant:

 !gc.png|thumbnail! 

> Performance degradation with session pools
> ------------------------------------------
>
>                 Key: DROOLS-3412
>                 URL: https://issues.jboss.org/browse/DROOLS-3412
>             Project: Drools
>          Issue Type: Bug
>            Reporter: Christian Liebhardt
>            Assignee: Mario Fusco
>            Priority: Major
>         Attachments: gc.png
>
>
> Hello,
> We've today updates to Drools 7.15 and as discussed with DROOLS-3228 we changed our code from calling _StatefulKnowledgeSessionImpl.reset_ ourselves to _KieSessionsPool_. However we then recognized that our application quickly became slower and slower over time (roughly after a few minutes of uptime, or a couple of hundred session create/dispose cycles). 
> I haven't yet found the reason what is causing the slow down. However I think there is a difference in how we reset our sessions before session pools and how session pools do it. Perhaps that is a lead.
> *What we did*
> # Create a session
> # Use the session
> # Dispose and reset the session and go back to 2 for the next facts
> *What happens with session pools*
> # Create a session
> # Use the session
> # Skip dispose (because of _pool != null_ in the dispose method), reset the session and go back to 2 for the next facts
> So the difference seems to be that with session pools the session doesn't get disposed before reset it called. If I do the same without session pools then I also see the same slow down. So it seems that something is left behind and causes a slow down. The results however seem to be correct, so the right consequences appear to be triggered.
> An example on how we use the session pool can be found here: https://github.com/liebharc/JavaRules/blob/master/src/main/java/com/github/liebharc/JavaRules/StatefulReusingDroolsEngine.java
> Thanks once more for your help.



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