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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3906) QJM: quorum timeout on failover with large log segment
Date Fri, 07 Sep 2012 21:30:07 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3906?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13450998#comment-13450998
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Todd Lipcon commented on HDFS-3906:
-----------------------------------

There are two ways to solve this:

1) Avoid log validation during the recovery step

This has the advantage of a faster failover

2) Increase the default timeouts

Originally the timeouts were set pretty low (~10sec) because I didn't think about the O(n)
nature of this step. It wouldn't be unreasonable to bump them to a couple minutes (only downside
would be a slower failure case when a quorum is actually down).


I'm going to make an attempt at solution #1, but if it gets too complex, will punt and do
solution #2.

                
> QJM: quorum timeout on failover with large log segment
> ------------------------------------------------------
>
>                 Key: HDFS-3906
>                 URL: https://issues.apache.org/jira/browse/HDFS-3906
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>    Affects Versions: QuorumJournalManager (HDFS-3077)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>
> In doing some stress tests, I ran into an issue with failover if the current edit log
segment written by the old active is large. With a 327MB log segment containing 6.4M transactions,
the JN took ~11 seconds to read and validate it during the recovery step. This was longer
than the 10 second timeout for createNewEpoch, which caused the recovery to fail.

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