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From "Torsten Feig (JIRA)" <j...@apache.org>
Subject [jira] Commented: (POOL-130) GenericObjectPool.Evictor creates new objects although exactly minIdle objects are idle
Date Wed, 29 Oct 2008 11:15:44 GMT

    [ https://issues.apache.org/jira/browse/POOL-130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12643467#action_12643467
] 

Torsten Feig commented on POOL-130:
-----------------------------------

In my case, the creation is probably not very expensive, but the outcome is ugly anyway: we
use GenericObjectPool as a thread pool. Every object created is a thread with a unique name
(basename + incremented counter) so to tell them apart (in logs or threaddumps). We'd like
to have 10 minIdle threads for a quick response to average workload. When the application
runs a while (i.e. for days), there may however be no work for these threads at all. So the
operations department frowns when looking into the logs and seeing ridiculously high thread
counters.

I haven't looked into the source code and can therefor not provide a patch. But it appears
to me that it should be quite simple as this "churn" of idle objects seems to be an additional
functionality - just cut out the code that destroys und recreates idle objects.

> GenericObjectPool.Evictor creates new objects although exactly minIdle objects are idle
> ---------------------------------------------------------------------------------------
>
>                 Key: POOL-130
>                 URL: https://issues.apache.org/jira/browse/POOL-130
>             Project: Commons Pool
>          Issue Type: Bug
>    Affects Versions: 1.2, 1.4
>            Reporter: Torsten Feig
>
> When you 
> - create a GenericObjectPool with these parameters: maxActive=100, maxIdle=100, minIdle=10,
timeBetweenEvictionRunsMillis=360000 (1h), minEvictableIdleTimeMillis=30000 (5min)
> - preload the 10 minIdle objects (10x borrowObject() + returnObject)
> you have a pool with 10 idle objects.
> Then every 1h the evictor destroys the 10 idle objects and creates 10 new ones. Why?
After all, creating and tearing down pool objects is likely to be expensive. So why destroy
the old objects when they exactly represent the minIdle objects? I don't see any need for
this.

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