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https://issues.apache.org/jira/browse/POOL-413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17772042#comment-17772042
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Phil Steitz commented on POOL-413:
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One option to consider here is to use the native capacity management capability
of LinkedBlockingDeque for the final (or other) maxIdle check. We would not
want to raise ISE as the public method does, but instead examine the boolean
returned by LinkFirst/LinkLast That check is made while holding its internal
lock so would be fully threadsafe.
> [GOP] Race condition while returning objects. maxIdle is ignored
> ----------------------------------------------------------------
>
> Key: POOL-413
> URL: https://issues.apache.org/jira/browse/POOL-413
> Project: Commons Pool
> Issue Type: Bug
> Reporter: Adrien Bernard
> Priority: Major
> Attachments:
> 0001-Add-test-to-reproduce-concurrency-issue-when-returni.patch
>
>
> In a GenericObjectPool it is possible to configure a maximum number of idle
> objects to be kept by the pool while they are not in use.
> In unfortunate circumstances, if several threads return an object to the pool
> at the same time, the check on the maximum number of idle objects may be
> dismissed. This results in pool keeping more idle objects than configured.
> I have build a unit test to reproduce the issue. I attach it as a patch made
> on top of release 2.12.0. On my machine it randomly fails with a 10% rate.
> Looking into the source code of the returnObject method of the GOP, it seems
> that there is no synchronisation between the moment the check is made for the
> maxIdle configuration and the moment the object is destroyed :
> {code:java}
> final int maxIdleSave = getMaxIdle();
> if (isClosed() || maxIdleSave > -1 && maxIdleSave <= idleObjects.size()) {
> try {
> destroy(p, DestroyMode.NORMAL);
> } catch (final Exception e) {
> swallowException(e);
> }
> try {
> ensureIdle(1, false);
> } catch (final Exception e) {
> swallowException(e);
> }
> } {code}
> Have you thoughts on this ?
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