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From "Nicolas Spiegelberg (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5332) Deterministic Compaction Jitter
Date Mon, 20 Feb 2012 02:33:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13211642#comment-13211642
] 

Nicolas Spiegelberg commented on HBASE-5332:
--------------------------------------------

@Lars: note that the operation you describe is operating on a double and converting to a long
at the end, so there is no loss of granularity.  Also note that the other proposed changes
would 2x and 3x the jitter from the user-configured percentage value.
                
> Deterministic Compaction Jitter
> -------------------------------
>
>                 Key: HBASE-5332
>                 URL: https://issues.apache.org/jira/browse/HBASE-5332
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Nicolas Spiegelberg
>            Assignee: Nicolas Spiegelberg
>            Priority: Minor
>         Attachments: D1785.1.patch, D1785.2.patch
>
>
> Currently, we add jitter to a compaction using "delay + jitter*(1 - 2*Math.random())".
 Since this is non-deterministic, we can get major compaction storms on server restart as
half the Stores that were set to "delay + jitter" will now be set to "delay - jitter".  We
need a more deterministic way to jitter major compactions so this information can persist
across server restarts.

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