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Date: Tue, 21 Jun 2011 05:05:47 +0000 (UTC)
From: "Todd Lipcon (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-2093) 1073: Handle case where an entirely
 empty log is left during NN crash
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    [ https://issues.apache.org/jira/browse/HDFS-2093?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13052347#comment-13052347 ] 

Todd Lipcon commented on HDFS-2093:
-----------------------------------

The really good news here is that the robustness of this design even in the presence of bugs proved itself - I removed the nonsense log file and the NN started with no corruption, 2NN checkpointed happily, no data lost.

> 1073: Handle case where an entirely empty log is left during NN crash
> ---------------------------------------------------------------------
>
>                 Key: HDFS-2093
>                 URL: https://issues.apache.org/jira/browse/HDFS-2093
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: name-node
>    Affects Versions: Edit log branch (HDFS-1073)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: Edit log branch (HDFS-1073)
>
>
> In fault-testing the HDFS-1073 branch, I saw the following situation:
> - NN has two storage directories, but one is in failed state
> - NN starts to roll edits logs to edits_inprogress_5160285
> - NN then crashes
> - on restart, it detects the truncated log, but since it has 0 txns, it finalizes it to the nonsense log name edits_5160285-5160284.
> - It then starts logs again at edits_inprogress_5160285.
> - After this point, no checkpoints or future NN startups succeed since there are two logs starting with the same txid

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