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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4238) [HA] Standby namenode should not do purging of shared storage edits.
Date Thu, 29 Nov 2012 18:58:59 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4238?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13506674#comment-13506674
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Todd Lipcon commented on HDFS-4238:
-----------------------------------

Hi Vinay. I agree it's a bug if the SBN is purging edits from the shared storage. However,
I don't follow the scenario you mentioned:

bq. >> After some time Active NN is restarted and StandBy NN switched to Active.
bq. Now current Standby not able to load any edits from shared storage, as expected edits
are not present in shared storage. Its keep running idle.

By "current Standby", do you mean the one that was Active prior to the restart?

Just to clarify, there was no permanent data loss here - just that you had to manually copy
one of the checkpoints from the new Active over to the new Standby, and restart the new Standby
before you could resynchronize?
                
> [HA] Standby namenode should not do purging of shared storage edits.
> --------------------------------------------------------------------
>
>                 Key: HDFS-4238
>                 URL: https://issues.apache.org/jira/browse/HDFS-4238
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: ha
>    Affects Versions: 3.0.0, 2.0.2-alpha
>            Reporter: Vinay
>
> This happened in our cluster,
> >> Standby NN was keep doing checkpoint every one hour and uploading to Active
NN was continuously failing due to some kerberos issue and nobody noticed this, since Active
was servicing properly.
> >> Active NN was up for long time with fsimage having very least transaction.
> >> Standby NN has saved the checkpoint in its name dir and purged the txns >
1000000 from shared storage ( includes edits which are not present in Active NN's fsimage)
> >> After some time Active NN is restarted and StandBy NN switched to Active.
> Now current Standby not able to load any edits from shared storage, as expected edits
are not present in shared storage. Its keep running idle.
> So {{editLog.purgeLogsOlderThan(purgeLogsFrom);}} always should be called from Active
NameNode.

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