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Posted to issues@nifi.apache.org by "Joseph Gresock (JIRA)" <ji...@apache.org> on 2016/09/30 10:14:20 UTC
[jira] [Updated] (NIFI-2848) Queues aren't fairly drained when
leading to a single component
[ https://issues.apache.org/jira/browse/NIFI-2848?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Joseph Gresock updated NIFI-2848:
---------------------------------
Attachment: Backpressure_prioritization_test.xml
> Queues aren't fairly drained when leading to a single component
> ---------------------------------------------------------------
>
> Key: NIFI-2848
> URL: https://issues.apache.org/jira/browse/NIFI-2848
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Core Framework
> Affects Versions: 1.0.0, 0.7.0
> Reporter: Joseph Gresock
> Attachments: Backpressure_prioritization_test.xml
>
>
> Consider the scenario where multiple queues lead to a single component and all of them are full due to back pressure. With the attached template, it is easily observable that once a single queue starts to drain due to relieved back pressure, it will continue to drain as long as it has incoming flow files. This means that if there's a constant flow of incoming flow files to this queue, the other two queues will never be drained (at least, that's my theory based on an hour of observation).
> To reproduce this:
> # Load the template into NiFi 1.0.0
> # Play all three GenerateFlowFile processors, but not the UpdateAttribute processor (this simulates backpressure). Wait until each queue has 1,000 flow files (max backpressure)
> # Stop the GenerateFlowFile processors, and play the UpdateAttribute processor (this relieves the backpressure)
> # Observe which queue has started to drain, and start its GenerateFlowFile processor
> # Observe that the other two queues remain full indefinitely, while the draining queue continues to replenish and be drained indefinitely
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