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From "Aaron T. Myers (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3725) Fix QJM startup when individual JNs have gaps
Date Mon, 30 Jul 2012 23:26:35 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3725?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13425375#comment-13425375
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Aaron T. Myers commented on HDFS-3725:
--------------------------------------

Makes sense. Thanks for the explanation.

+1, the patch looks good to me.
                
> Fix QJM startup when individual JNs have gaps
> ---------------------------------------------
>
>                 Key: HDFS-3725
>                 URL: https://issues.apache.org/jira/browse/HDFS-3725
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha
>    Affects Versions: QuorumJournalManager (HDFS-3077)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>         Attachments: hdfs-3725.txt
>
>
> This fixes a bug in the HDFS-3077 branch:
> If one of the JNs goes down and comes back up, it may have a discontiguous set of logs
in its storage directories. This means that a future {{getEditLogManifest}} call will return
a manifest that has gaps - eg it may have txn 1-3 and 7-9 but be missing 4-6. This is OK because
it's guaranteed that a quorum of JNs do have those edits elsewhere.
> This situation currently causes an exception since the RemoteEditLogManifest constructor
verifies that the returned log files form a contiguous set of edits. That was true for the
NameNode but no longer true for this new usage.

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