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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1508) Ability to do savenamespace without being in safemode
Date Tue, 07 Dec 2010 20:19:09 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1508?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12968937#action_12968937
] 

dhruba borthakur commented on HDFS-1508:
----------------------------------------

hi konstantin, your suggestion of restarting a daemon that is supposed to be continuously
running does not work very well from an operartions-point-of-view. In most of our clusters,
we have alerts and monitoring to detect failed daemons. If you kill and restart a daemon,
all those alerts fire immediately. 

You could argue that there could be a new command-line utility that talks to the Secondary
and requests an immediate checkpoint (instead of waiting for the next half hour), but that
is a round-about way of doing things, e.g it does not handle the case when one is not running
the Secondary at all. 

> Ability to do savenamespace without being in safemode
> -----------------------------------------------------
>
>                 Key: HDFS-1508
>                 URL: https://issues.apache.org/jira/browse/HDFS-1508
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: savenamespaceWithoutSafemode.txt, savenamespaceWithoutSafemode2.txt,
savenamespaceWithoutSafemode3.txt, savenamespaceWithoutSafemode4.txt
>
>
> In the current code, the administrator can run savenamespace only after putting the namenode
in safemode. This means that applications that are writing to HDFS encounters errors because
the NN is in safemode. We would like to allow saveNamespace even when the namenode is not
in safemode.
> The savenamespace command already acquires the FSNamesystem writelock. There is no need
to require that the namenode is in safemode too.

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