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https://issues.apache.org/jira/browse/NIFI-1085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14980711#comment-14980711
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Michael Moser commented on NIFI-1085:
-------------------------------------
And to be fair, we see the symptoms most often when our heap usage on the NCM
is near its max capacity and garbage collection begins to take a lot more time
overall than normal. Increasing the heap size mitigates this to some extent.
> WebClusterManager starves immutable API requests under heavy load conditions
> ----------------------------------------------------------------------------
>
> Key: NIFI-1085
> URL: https://issues.apache.org/jira/browse/NIFI-1085
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Core Framework
> Affects Versions: 0.3.0
> Reporter: Michael Moser
>
> With a 6 node cluster with thousands of components on the graph, we noticed
> that the ReentrantReadWriteLock in WebClusterManager can starve NiFi Web
> Server threads that are waiting on the read lock.
> Thread dumps shows the HeartbeatMonitoringTimerTask thread holding the write
> lock while many Web Server threads are parked waiting on the read lock.
> Modify the ReentrantReadWriteLock to operate in fair mode (to give the lock
> to threads waiting the longest, such as those wanting the read lock).
> Modify the HearbeatMonitoringTimerTask timer to not be scheduleAtFixedRate()
> but instead use schedule() to execute it less often if garbage collection
> blocks it.
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