A ConcurrentModificationException inside BaseWrapperManagedConnection class freezes the connection pool.

[epeire]

Hello :)

We currently have issues with an unexpected ConcurrentModificationException inside the BaseWrapperManagedConnection class.
Under load, this leads to a complete freeze of the connection pool (which is then unable to deliver new connections anymore) - we are then forced to restart the application.

We currently use a IronJacamar 1.5.4.Final; the problem has been found on versions 1.4.38, 1.5.2 and 1.5.4
We had no problem with version 1.4.9.

This problem might have been been introduced with version ~1.4.20, in a change related to JBJCA-1396.

Here is an except of the stacktrace :

stacktrace_part.txt

The problem is caused by the BaseWrapperManagedConnection#cleanup() method (line 341)
It iterates on a set, and calls #closeHandle (line 347) on each element, which calls returnHandle(), which finally removes an element from the set (from outside the iterator ^^)
When the set contains more than one element, the iterator detects the change and throws the exception.

Iterating on a copy of the set solved the problem for us (cf PR)

[tadamski]

Hello @epeire

Thanks for detailed description and analysis. I have created https://issues.redhat.com/browse/JBJCA-1446 to track this issue and I'm looking into this.