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https://issues.apache.org/jira/browse/NIFI-241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14275468#comment-14275468
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Mark Payne commented on NIFI-241:
---------------------------------
Mike,
You can definitely use the @OnAdded, @OnRemoved, @OnShutdown annotations, but
their uses should be quite rare. @OnAdded is used when the Processor is added
to the graph and never again, including on restart of NiFi, so establishing a
connection pool should not be done in @OnAdded. @OnRemoved is a good time to
remove a state file, for example. @OnShutdown is used only in order to be a
good steward and clean up open connections, etc., as it is not guaranteed to be
called on shutdown (kill -9 for instance doesn't allow this to happen).
> Framework FingerprintFactory begins processor life cycle but does not finish
> ----------------------------------------------------------------------------
>
> Key: NIFI-241
> URL: https://issues.apache.org/jira/browse/NIFI-241
> Project: Apache NiFi
> Issue Type: Bug
> Components: Core Framework
> Reporter: Michael Moser
> Assignee: Mark Payne
> Fix For: 0.0.1
>
>
> The FingerprintFactory will create Processor objects and invoke their
> initialize() and @OnAdded methods. If a Processor uses system resources,
> these methods are where those resources are allocated. But, those processors
> are never disposed by calling their @OnRemoved or @OnShutdown methods. This
> may result in system resource leaks, depending on how processors are
> implemented.
> To reproduce, add a processor to the NiFi graph and restart NiFi. Note that
> initialize() and @OnAdded is called at least twice (I observed 3 times) as
> NiFi starts. The getIdentifier() is different for each invocation. Shutdown
> NiFi and observe that @OnShutdown is called once.
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