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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-3900) QJM: avoid validating log segments on log rolls
Date Fri, 07 Sep 2012 03:41:07 GMT

     [ https://issues.apache.org/jira/browse/HDFS-3900?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon updated HDFS-3900:
------------------------------

    Attachment: hdfs-3900.txt

Attached patch fixes the issue. I also did some code cleanup around the treatment of the {{curSegmentTxId}}
variable, which was used somewhat inconsistently before. Now it's only set when a segment
is open, which is a little cleaner.
                
> QJM: avoid validating log segments on log rolls
> -----------------------------------------------
>
>                 Key: HDFS-3900
>                 URL: https://issues.apache.org/jira/browse/HDFS-3900
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>    Affects Versions: QuorumJournalManager (HDFS-3077)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: hdfs-3900.txt
>
>
> Currently, we are paranoid and validate every log segment when it is finalized. For the
a log segment that has been written entirely by one writer, with no recovery in between, this
is overly paranoid (we don't do this for local journals). It also causes log rolls to be slow
and take time linear in the size of the segment. Instead, we should optimize this path to
simply trust that the segment is correct so long as the txids match up as expected.

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