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https://issues.apache.org/jira/browse/YARN-10789?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17352401#comment-17352401
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Tarun Parimi commented on YARN-10789:
-------------------------------------
Thanks [~sunilg]. Added warn log in the latest patch.
> RM HA startup can fail due to race conditions in ZKConfigurationStore
> ---------------------------------------------------------------------
>
> Key: YARN-10789
> URL: https://issues.apache.org/jira/browse/YARN-10789
> Project: Hadoop YARN
> Issue Type: Bug
> Affects Versions: 3.0.0
> Reporter: Tarun Parimi
> Assignee: Tarun Parimi
> Priority: Major
> Attachments: YARN-10789.001.patch, YARN-10789.002.patch
>
>
> We are observing below error randomly during hadoop install and RM initial
> startup when HA is enabled and yarn.scheduler.configuration.store.class=zk is
> configured. This causes one of the RMs to not startup.
> {code:java}
> 2021-05-26 12:59:18,986 INFO org.apache.hadoop.service.AbstractService:
> Service RMActiveServices failed in state INITED
> org.apache.hadoop.service.ServiceStateException: java.io.IOException:
> org.apache.zookeeper.KeeperException$NodeExistsException: KeeperErrorCode =
> NodeExists for /confstore/CONF_STORE
> {code}
> We are trying to create the znode /confstore/CONF_STORE when we initialize
> the ZKConfigurationStore. But the problem is that the ZKConfigurationStore is
> initialized when CapacityScheduler does a serviceInit. This serviceInit is
> done by both Active and Standby RM. So we can run into a race condition when
> both Active and Standby try to create the same znode when both RM are started
> at same time.
> ZKRMStateStore on the other hand avoids such race conditions, by creating the
> znodes only after serviceStart. serviceStart only happens for the active RM
> which won the leader election, unlike serviceInit which happens irrespective
> of leader election.
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