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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3556) Substitute the synchronized code in MD5Hash to avoid lock contention. Use ThreadLocal instead.
Date Fri, 13 Jun 2008 20:25:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12604964#action_12604964
] 

Doug Cutting commented on HADOOP-3556:
--------------------------------------

+1 This looks good to me.

> Substitute the synchronized code in MD5Hash to avoid lock contention. Use ThreadLocal
instead.
> ----------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-3556
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3556
>             Project: Hadoop Core
>          Issue Type: Improvement
>            Reporter: Iván de Prado
>         Attachments: MD5Hash-ThreadLocal.patch
>
>
> Currently the MD5Hash class uses a singleton instance of the MessageDigester. The access
to this instance is synchronized, so MD5Hash has performance problems when used from several
Threads. I propose to substitute the singleton instance by a TheadLocal instances cache. I
will provide a patch.

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