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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1792) Add code to detect valid length of an edits file
Date Tue, 05 Apr 2011 05:39:06 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1792?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13015769#comment-13015769
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dhruba borthakur commented on HDFS-1792:
----------------------------------------

from my understanding, this is not guaranteed to work. The jvm call that we use to preallocate
the editlog is not guaranteed to fill it up with zeros, instead the part that was extended
is filled with "undefined" values. http://tinyurl.com/3b6e93k



> Add code to detect valid length of an edits file
> ------------------------------------------------
>
>                 Key: HDFS-1792
>                 URL: https://issues.apache.org/jira/browse/HDFS-1792
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>    Affects Versions: Edit log branch (HDFS-1073)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: Edit log branch (HDFS-1073)
>
>         Attachments: hdfs-1792.txt
>
>
> In some edit log corruption situations, it's useful to be able to determine the "valid"
length of an edit log. For this JIRA we define "valid" as the length of the file excluding
any trailing 0x00 bytes, usually left there by the preallocation done while writing. In the
future this API can be extended to look at edit checksums, etc.

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