Adrien Bernard created POOL-413:
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Summary: [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
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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