[jira] [Updated] (HADOOP-10251) Both NameNodes could be in STANDBY State if SNN network is unstable

["Vinay (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-10251?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vinay updated HADOOP-10251:
---------------------------

    Attachment: HADOOP-10251.patch

Attaching a patch for the above case. Please review

> Both NameNodes could be in STANDBY State if SNN network is unstable
> -------------------------------------------------------------------
>
>                 Key: HADOOP-10251
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10251
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: ha
>    Affects Versions: 2.2.0
>            Reporter: Vinay
>            Assignee: Vinay
>            Priority: Critical
>         Attachments: HADOOP-10251.patch
>
>
> Following corner scenario happened in one of our cluster.
> 1. NN1 was Active and NN2 was Standby
> 2. NN2 machine's network was slow 
> 3. NN1 got shutdown.
> 4. NN2 ZKFC got the notification and trying to check for old active for fencing. (This took little more time, again due to slow network)
> 5. In between, NN1 got restarted by our automatic monitoring, and ZKFC made it Active.
> 6. Now NN2 ZKFC got Old Active as NN2 and it did graceful fencing of NN1 to STANBY.
> 7. Before writing ActiveBreadCrumb to ZK, NN2 ZKFC got session timeout and got shutdown before making NN2 Active.
> *Now cluster having both NameNodes as STANDBY.*
> NN1 ZKFC still thinks that its nameNode is in Active state. 
> NN2 ZKFC waiting for election.



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