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Date: Tue, 24 Jan 2017 19:02:27 +0000 (UTC)
From: "Wiktor N (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
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Subject: [jira] [Commented] (JCS-171) Multiple CacheEventQueue.QProcessor
 spawned for the same cache region
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archived-at: Tue, 24 Jan 2017 19:02:47 -0000


    [ https://issues.apache.org/jira/browse/JCS-171?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15836453#comment-15836453 ] 

Wiktor N commented on JCS-171:
------------------------------

One of our users reported that he sees messages related in my opinion to this change:

{noformat}
java.util.concurrent.RejectedExecutionException: Task PutEvent for key: Bing aerial imagery:http://www.bing.com/maps/14/5836/9279 value: org.openstreetmap.josm.data.cache.BufferedImageCacheEntry@20ae54f3 rejected from java.util.concurrent.ThreadPoolExecutor@1bd0f37c[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 3898]
	at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2047)
	at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:823)
	at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1369)
	at org.apache.commons.jcs.engine.PooledCacheEventQueue.put(PooledCacheEventQueue.java:127)
	at org.apache.commons.jcs.engine.AbstractCacheEventQueue.addPutEvent(AbstractCacheEventQueue.java:187)
	at org.apache.commons.jcs.auxiliary.disk.AbstractDiskCache.update(AbstractDiskCache.java:215)
	at org.apache.commons.jcs.engine.control.CompositeCache.updateAuxiliaries(CompositeCache.java:368)
	at org.apache.commons.jcs.engine.control.CompositeCache.update(CompositeCache.java:253)
	at org.apache.commons.jcs.engine.control.CompositeCache.update(CompositeCache.java:205)
	at org.apache.commons.jcs.access.CacheAccess.put(CacheAccess.java:239)
{noformat}

I'll investigate further to check what's going on, as there is no clear way to reproduce. Though it doesn't affect stability.

> Multiple CacheEventQueue.QProcessor spawned for the same cache region
> ---------------------------------------------------------------------
>
>                 Key: JCS-171
>                 URL: https://issues.apache.org/jira/browse/JCS-171
>             Project: Commons JCS
>          Issue Type: Bug
>          Components: Composite Cache
>    Affects Versions: jcs-2.0
>            Reporter: Wiktor N
>            Assignee: Thomas Vandahl
>             Fix For: jcs-2.1
>
>         Attachments: CacheEventQueue.patch, jcs-perf-test.zip
>
>
> I noticed that running on new version of JCS I get multiple CacheEventQueue.QProcessor thread. They spawn from time to time.
> I've checked recent changes and changes few things in r1774925 look suspicious:
> 1. In previous code we spawned a new thread in synchronized section. This got us a guarantee, that there will be no two threads trying to spawn a new thread in the same time. Maybe some locking is needed around thread creation?
> 2. QProcessor uses isAlive() method. But this is defined by Thread.isAlive() while it should probably check for CacheEventQueue.this.isAlive()


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