Mark Payne created NIFI-12693:
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Summary: When Processor is removed, Python Process should be
notified asynchronously
Key: NIFI-12693
URL: https://issues.apache.org/jira/browse/NIFI-12693
Project: Apache NiFi
Issue Type: Bug
Components: Core Framework
Reporter: Mark Payne
Assignee: Mark Payne
Fix For: 2.0.0
When a Processor is removed, the PythonBridge is notified of the removal, and
it then notifies any relevant Python process. This is done synchronously during
the removal. I encountered two occurrences in which notifying the Python
process failed.
While the failure itself is not a huge concern, the handling of those failures
resulted in very bad outcomes. In the first instance, the communication with
the Python process was blocked on a socket read or write. As a result, the
Service Facade's lock was never released, and no web requests could be made;
they all blocked on the read lock. This resulted in requiring a restart of NiFi.
In the other scenario, the call did not block indefinitely but threw an
Exception. In this case, the associated Connections were never removed. As a
result, I could no longer navigate to that Process Group in the UI, or the UI
would have errors because there were Connections whose source or destination
didn't exist. This required manually removing those connections from the
flow.json file to recover.
Since the intention of this action is simply a notification so that the Python
process can cleanup after itself, this notification should be moved to a
background thread, so that any failures are simply logged without causing
problematic side effects.
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