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From "sam rash (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1186) 0.20: DNs should interrupt writers at start of recovery
Date Fri, 25 Jun 2010 00:00:52 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1186?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12882404#action_12882404

sam rash commented on HDFS-1186:

wait, why can't commitBlockSync on the NN just do the same check on genstamps?  if two primaries
start concurrent lease recoveries and split the remaining nodes as far as who wins in stamping,
and the NN can resolve the issue of who wins in the end?   then the loser will be marked as
an invalid and replication takes over to fix it

or i have this sinking feeling i am still missing something?

> 0.20: DNs should interrupt writers at start of recovery
> -------------------------------------------------------
>                 Key: HDFS-1186
>                 URL: https://issues.apache.org/jira/browse/HDFS-1186
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node
>    Affects Versions: 0.20-append
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Blocker
>         Attachments: hdfs-1186.txt
> When block recovery starts (eg due to NN recovering lease) it needs to interrupt any
writers currently writing to those blocks. Otherwise, an old writer (who hasn't realized he
lost his lease) can continue to write+sync to the blocks, and thus recovery ends up truncating
data that has been sync()ed.

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