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https://issues.apache.org/jira/browse/HADOOP-9459?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Todd Lipcon updated HADOOP-9459:
--------------------------------
Attachment: hdfs-4463.txt
Hey Vinay. The patch looks good. I took the liberty of updating it with a
couple of extra Preconditions checks to make sure we don't have any more code
paths which might trigger this issue. Let me know if you're OK with the
changes, and I'll commit this.
> ActiveStandbyElector can join election even before Service HEALTHY, and
> results in null data at ActiveBreadCrumb
> ----------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-9459
> URL: https://issues.apache.org/jira/browse/HADOOP-9459
> Project: Hadoop Common
> Issue Type: Bug
> Components: ha
> Affects Versions: 2.0.2-alpha
> Reporter: Vinay
> Assignee: Vinay
> Priority: Critical
> Attachments: HDFS-4463.patch, hdfs-4463.txt
>
>
> ActiveStandbyElector can store null at ActiveBreadCrumb in the below race
> condition. At further all failovers will fail resulting NPE.
> 1. ZKFC restarted.
> 2. due to machine busy, first zk connection is expired even before the health
> monitoring returned the status.
> 3. On re-establishment transitionToActive will be called, at this time
> appData will be null,
> 4. So now ActiveBreadCrumb will have null.
> 5. After this any failovers will fail throwing
> {noformat}java.lang.NullPointerException
> at
> org.apache.hadoop.util.StringUtils.byteToHexString(StringUtils.java:171)
> at
> org.apache.hadoop.ha.ActiveStandbyElector.fenceOldActive(ActiveStandbyElector.java:892)
> at
> org.apache.hadoop.ha.ActiveStandbyElector.becomeActive(ActiveStandbyElector.java:797)
> at
> org.apache.hadoop.ha.ActiveStandbyElector.processResult(ActiveStandbyElector.java:475)
> at
> org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:545)
> at
> org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:497){noformat}
> Should not join the election before service is HEALTHY
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