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https://issues.apache.org/jira/browse/YARN-11490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17721946#comment-17721946
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Szilard Nemeth commented on YARN-11490:
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Hi [~tdomok],
Nice finding.
I do agree with your statements.
1. The memory leak
{quote}
Revert YARN-11211, it's a nasty bug and the "leak" only causes problems if the
validation API is abused with unique queue names. Note that YARN-11211 did not
solve the leak problem either, details above.
{quote}
Good that you characterized the nature of the leak, I think it's okay to revert
YARN-11211 in this case.
Please file a separate bug ticket for the leak.
3. Validate separately:
{quote}
Spawn a separate process for configuration validation with the proper config /
state. Not sure if this is feasible or not, but it would be the cleanest.
{quote}
I agree that this would be the cleanest approach but given the current state of
the codebase I really doubt it's easy to implement.
> JMX QueueMetrics breaks after mutable config validation in CS
> -------------------------------------------------------------
>
> Key: YARN-11490
> URL: https://issues.apache.org/jira/browse/YARN-11490
> Project: Hadoop YARN
> Issue Type: Bug
> Components: capacityscheduler
> Affects Versions: 3.4.0
> Reporter: Tamas Domok
> Assignee: Tamas Domok
> Priority: Major
> Labels: pull-request-available
> Attachments: addqueue.xml, defaultqueue.json,
> hadoop-tdomok-resourcemanager-tdomok-MBP16.log, removequeue.xml,
> stopqueue.json
>
>
> Reproduction steps:
> 1. Submit a long running job
> {code}
> hadoop-3.4.0-SNAPSHOT/bin/yarn jar
> hadoop-3.4.0-SNAPSHOT/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-3.4.0-SNAPSHOT-tests.jar
> sleep -m 1 -r 1 -rt 1200000 -mt 20
> {code}
> 2. Verify that there is one running app
> {code}
> $ curl http://localhost:8088/ws/v1/cluster/metrics | jq
> {code}
> 3. Verify that the JMX endpoint reports 1 running app as well
> {code}
> $ curl http://localhost:8088/jmx | jq
> {code}
> 4. Validate the configuration (x2)
> {code}
> $ curl -X POST -H 'Content-Type: application/json' -d @defaultqueue.json
> localhost:8088/ws/v1/cluster/scheduler-conf/validate
> $ cat defaultqueue.json
> {"update-queue":{"queue-name":"root.default","params":{"entry":{"key":"maximum-applications","value":"100"}}},"subClusterId":"","global":null,"global-updates":null}
> {code}
> 5. Check 2. and 3. again. The cluster metrics should still work but the JMX
> endpoint will show 0 running apps, that's the bug.
> It is caused by YARN-11211, reverting that patch (or only removing the
> _QueueMetrics.clearQueueMetrics();_ line) fixes the issue. But I think that
> would re-introduce the memory leak.
> It looks like the QUEUE_METRICS hash map is "add-only", the
> clearQueueMetrics() was only called from ResourceManager.reinitialize()
> method (transitionToActive/transitionToStandby) prior to YARN-11211.
> Constantly adding and removing queues with unique names would cause a leak as
> well, because there is no remove from QUEUE_METRICS, so it is not just the
> validation API that has this problem.
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