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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6203) check other namenode's state before HAadmin transitionToActive
Date Tue, 08 Apr 2014 21:39:16 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13963476#comment-13963476

Jing Zhao commented on HDFS-6203:

Currently if users enable the automatic failover, the manual transitionToActive operation
is disallowed, unless a "forcemanual" option is given and the user confirms the operation.
Also the prompt msg states the risk of the operation. Do you mean we should also do this for
non-automatic failover case?

For checking other NN's state, if we add the check into the transitionToActive method, we
cannot still guarantee that the other NN will not transition to active after the checking.
Thus I think the checking here will not be very useful.

> check other namenode's state before HAadmin transitionToActive
> --------------------------------------------------------------
>                 Key: HDFS-6203
>                 URL: https://issues.apache.org/jira/browse/HDFS-6203
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: ha
>    Affects Versions: 2.3.0
>            Reporter: patrick white
> Current behavior is that the HAadmin -transitionToActive command will complete the transition
to Active even if the other namenode is already in Active state. This is not an allowed condition
and should be handled by fencing, however setting both namenode's active can happen accidentally
with relative ease, especially in a production environment when performing manual maintenance
> If this situation does occur it is very serious and will likely cause data loss, or best
case, require a difficult recovery to avoid data loss.
> This is requesting an enhancement to haadmin's -transitionToActive command, to have HAadmin
check the Active state of the other namenode before completing the transition. If the other
namenode is Active, then fail the request due to other nn already-active.
> Not sure if there is a scenario where both namenode's being Active is valid or desired,
but to maintain functional compatibility a 'force' parameter could be added to  override this
check and allow previous behavior.

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