Tarun Parimi created YARN-10789:
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Summary: 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
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 cause one of the RM's 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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