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https://issues.apache.org/jira/browse/HADOOP-3556?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Iván de Prado updated HADOOP-3556:
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    Attachment: 3556.patch

> 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: 3556.patch, 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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