Github user markap14 commented on the issue:
https://github.com/apache/nifi/pull/2722
@joewitt I think I understand now what you were seeing. If I create two
different DebugFlow processors, each with a validation pause of 10 seconds, and
then I create an UpdateAttribute and configure each of them in quick
succession, I see UpdateAttribute in a 'Validating' state for many seconds. I
have created a new JIRA for this, though, NIFI-5222, as I don't think it's
something that should really block merging this PR in. The issue appears to be
that we kick off validation 3 times each time that we click "Update" and so if
we update both DebugFlow processors, we end up kicking off 6 validation tasks
instead of 2, and that ends up blocking UpdateAttribute since we have only 5
threads in the pool.
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