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https://issues.apache.org/jira/browse/NIFI-11677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17731640#comment-17731640
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Isha Lamboo commented on NIFI-11677:
------------------------------------
>From the Developers mailing list:
-----Oorspronkelijk bericht-----
Van: Bryan Bende <[email protected]>
Verzonden: maandag 12 juni 2023 16:10
Aan: [email protected]
Onderwerp: Re: DeleteHDFS behavior when idle
The processor has @TriggerWhenEmpty so it is going to keep executing regardless
of whether the incoming queue has data or not. I believe this was done early on
for some processors that used Kerberos in order to allow the processor to have
a chance to renew the Kerberos ticket, however we since moved away from need to
do this, so unless there is another reason for having that, I would think it
can be removed.
> DeleteHDFS runs tasks with empty incoming connection
> ----------------------------------------------------
>
> Key: NIFI-11677
> URL: https://issues.apache.org/jira/browse/NIFI-11677
> Project: Apache NiFi
> Issue Type: Bug
> Components: Extensions
> Affects Versions: 1.18.0, 1.19.1
> Environment: 64bit redhat linux, java 1.8.0_352, 3 node cluster
> Reporter: Isha Lamboo
> Priority: Minor
>
> The DeleteHDFS processor can operate either with or without an incoming
> connection. When operating *with* an incoming connection that has no
> flowfiles, it still registers as executing tasks and taking a small amount of
> time (in the range of 50-100 millis on our clusters). In our case this
> results in ~200 processors each running 800-1000 tasks per 5 minutes on a 3
> node cluster with 16 CPUs per node.
> This is in contrast to the PutHDFS with an incoming connection which shows as
> 0 tasks/0 millis.
> Reproduce the situation by connecting a (stopped) ListHDFS processor to a
> DeleteHDFS processor with a variable for the path. Start the DeleteHDFS and
> refresh for statistics update.
> Having compared the code for PutHDFS and DeleteHDFS I think I see the cause:
> PutHDFS has this in its OnTrigger method:
> {code:java}
> final FlowFile flowFile = session.get();
> if (flowFile == null) {
> return;
> } {code}
> DeleteHDFS has this in the OnTrigger method:
> {code:java}
> final FlowFile originalFlowFile = session.get();
> // If this processor has an incoming connection, then do not run
> unless a
> // FlowFile is actually sent through
> if (originalFlowFile == null && context.hasIncomingConnection()) {
> context.yield();
> return;
> } {code}
> I'm guessing that the extra context.yield() causes the framework to execute
> some administration tasks and update counters, where it does not for PutHDFS.
> I don't know how much overhead this causes, probably very little, but I'm
> trying to improve performance on a cluster with thread starvation issues and
> high CPU usage and these keep popping up in the summaries looking bad when I
> think they shouldn't.
> The likely solution is to only perform the context.yield() when
> hasIncomingConnection() returns false.
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