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https://issues.apache.org/jira/browse/NIFI-1085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14997177#comment-14997177
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Mark Payne commented on NIFI-1085:
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[~mosermw] - the code changes look reasonable. Created a simple cluster to
verify functionality and it all appears okay. +1 - feel free to merge in
changes. Thanks!
> 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
> Fix For: 0.4.0
>
>
> 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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