hadoop-hdfs-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1260) 0.20: Block lost when multiple DNs trying to recover it to different genstamps
Date Wed, 23 Jun 2010 00:45:50 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12881490#action_12881490

Todd Lipcon commented on HDFS-1260:

To confirm the suspicion above, I had the operator rename the meta block back to _7094, and
the next recovery attempt succeeded.

> 0.20: Block lost when multiple DNs trying to recover it to different genstamps
> ------------------------------------------------------------------------------
>                 Key: HDFS-1260
>                 URL: https://issues.apache.org/jira/browse/HDFS-1260
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 0.20-append
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.20-append
> Saw this issue on a cluster where some ops people were doing network changes without
shutting down DNs first. So, recovery ended up getting started at multiple different DNs at
the same time, and some race condition occurred that caused a block to get permanently stuck
in recovery mode. What seems to have happened is the following:
> - FSDataset.tryUpdateBlock called with old genstamp 7091, new genstamp 7094, while the
block in the volumeMap (and on filesystem) was genstamp 7093
> - we find the block file and meta file based on block ID only, without comparing gen
> - we rename the meta file to the new genstamp _7094
> - in updateBlockMap, we do comparison in the volumeMap by oldblock *without* wildcard
GS, so it does *not* update volumeMap
> - validateBlockMetaData now fails with "blk_7739687463244048122_7094 does not exist in
blocks map"
> After this point, all future recovery attempts to that node fail in getBlockMetaDataInfo,
since it finds the _7094 gen stamp in getStoredBlock (since the meta file got renamed above)
and then fails since _7094 isn't in volumeMap in validateBlockMetadata
> Making a unit test for this is probably going to be difficult, but doable.

This message is automatically generated by JIRA.
You can reply to this email to add a comment to the issue online.

View raw message