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Date: Tue, 6 Mar 2012 22:57:59 +0000 (UTC)
From: "Eli Collins (Commented) (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-2872) Add sanity checks during edits
 loading that generation stamps are non-decreasing
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    [ https://issues.apache.org/jira/browse/HDFS-2872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13223759#comment-13223759 ] 

Eli Collins commented on HDFS-2872:
-----------------------------------

Some nits, otherwise looks great.

- I'd throw IOE instead of InvalidGenStampException to be consisten with the rest of the method
- You don't need to use StringBuilder since Java optimizes string concats and this code path is rarely run
- The patch has uses tabs instead of spaces

                
> Add sanity checks during edits loading that generation stamps are non-decreasing
> --------------------------------------------------------------------------------
>
>                 Key: HDFS-2872
>                 URL: https://issues.apache.org/jira/browse/HDFS-2872
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 1.0.0
>            Reporter: Todd Lipcon
>            Assignee: Colin Patrick McCabe
>         Attachments: HDFS-2872-branch-1.patch, HDFS-2872-branch-1.patch2, HDFS-2872.patch
>
>
> In 0.23 and later versions, we have a txid per edit, and the loading process verifies that there are no gaps. Lacking this in 1.0, we can use generation stamps as a proxy - the OP_SET_GENERATION_STAMP opcode should never result in a decreased genstamp. If it does, that would indicate that the edits are corrupt, or older edits are being applied to a newer checkpoint, for example.

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