NIFI-6391 Prevent excessive JMS connections

[slyouts]

Thank you for submitting a contribution to Apache NiFi.

Excessive connections created when get/publish operations continually fail

Description of PR

PublishJMS repeatedly threw "ResourceAllocationException: too many open connections" after successive publish failures due to issues on the remote JMS Broker. The cause of this is the specification and implementation of the JMSConnectionFactoryProviderDefinition.resetConnectionFactory(ConnectionFactory cf) method. Setting the ConnectionFactory to null may well indeed close connections upon 'destruction', but it may take awhile for the GC to run; in the meantime, more connections are opened. The connections need to be manually closed rather than waiting for a GC.

From AbstractJMSProcessor.onTrigger(), need to call worker.shutdown() prior to resetConnectionFactory().

Also, noticed some problems iwth the ConnectionFactoryProviderDefinition implementatoins wrt the resetConnectionFactory methods. The factory is nulled but never re-initialized but for onEnabled(); which will lead to a NPE at some point.

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[thenatog]

How can I replicate the original issue to confirm this PR fixes it?

[slyouts]

The issue involves several areas of configuration, plus having a JMS broker that continually fails on Put requests. The parameters are the GC interval for the NiFi JVM, the max number of open sockets for your OS, and a Put rate that is high enough to exceed the max number of open sockets within the GC interval. How one puts this all together is beyond me. However, I've provided a detailed explanation of the problem in the ticket and examination of the code, with the understanding that the connections are cached, reveals the existence of a resource leak.
While there may be better ways to deal with the cached connections, given the API I have to work with what I've offered is my best effort to deal with the problem.

[slyouts]

Added this comment to the PR, but replying just in case (I'm uncertain of who get's PR emails): The issue involves several areas of configuration, plus having a JMS broker that continually fails on Put requests. The parameters are the GC interval for the NiFi JVM, the max number of open sockets for your OS, and a Put rate that is high enough to exceed the max number of open sockets within the GC interval. How one puts this all together is beyond me. However, I've provided a detailed explanation of the problem in the ticket and examination of the code, with the understanding that the connections are cached, reveals the existence of a resource leak. While there may be better ways to deal with the cached connections, given the API I have to work with what I've offered is my best effort to deal with the problem. Steve

…

On Fri, Jul 12, 2019 at 7:36 PM thenatog ***@***.***> wrote: How can I replicate the original issue to confirm this PR fixes it? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#3555?email_source=notifications&email_token=AMAXDVEVWJUL2HZ2WBUOJNLP7EIQNA5CNFSM4H3WJORKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODZ3DNHA#issuecomment-511063708>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AMAXDVFIN6SM7I3QXYKMF33P7EIQNANCNFSM4H3WJORA> .

[github-actions]

We're marking this PR as stale due to lack of updates in the past few months. If after another couple of weeks the stale label has not been removed this PR will be closed. This stale marker and eventual auto close does not indicate a judgement of the PR just lack of reviewer bandwidth and helps us keep the PR queue more manageable. If you would like this PR re-opened you can do so and a committer can remove the stale tag. Or you can open a new PR. Try to help review other PRs to increase PR review bandwidth which in turn helps yours.