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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HDFS-1521) Persist transaction ID on disk between NN restarts
Date Tue, 14 Dec 2010 09:17:22 GMT

     [ https://issues.apache.org/jira/browse/HDFS-1521?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon updated HDFS-1521:
------------------------------

    Attachment: hdfs-1521.3.txt

This patch switches to logging a txid for every edit and verifying strict sequential ordering
on load.

I also left the txid in the header - it seemed to me this is advantageous just as something
that *must* be there at the top of every edit file. If others disagree we can take it out.

Added some basic tests as well to ensure we can still read the old format.

> Persist transaction ID on disk between NN restarts
> --------------------------------------------------
>
>                 Key: HDFS-1521
>                 URL: https://issues.apache.org/jira/browse/HDFS-1521
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>    Affects Versions: 0.22.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: 0.22.0
>
>         Attachments: hdfs-1521.3.txt, hdfs-1521.txt, hdfs-1521.txt
>
>
> For HDFS-1073 and other future work, we'd like to have the concept of a transaction ID
that is persisted on disk with the image/edits. We already have this concept in the NameNode
but it resets to 0 on restart. We can also use this txid to replace the _checkpointTime_ field,
I believe.

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