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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-5381) ExtendedBlock#hashCode should use both blockId and block pool ID
Date Thu, 17 Oct 2013 17:47:42 GMT

     [ https://issues.apache.org/jira/browse/HDFS-5381?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Colin Patrick McCabe updated HDFS-5381:
---------------------------------------

    Component/s:     (was: datanode)
                     (was: namenode)
                 federation

> ExtendedBlock#hashCode should use both blockId and block pool ID
> ----------------------------------------------------------------
>
>                 Key: HDFS-5381
>                 URL: https://issues.apache.org/jira/browse/HDFS-5381
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: federation
>    Affects Versions: 2.3.0
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>            Priority: Minor
>         Attachments: HDFS-5381.001.patch
>
>
> {{ExtendedBlock#hashCode}} contains both a block pool ID and a block ID.  The {{equals}}
function checks both.  However, {{hashCode}} only uses block ID.  Since HDFS-4645, block IDs
are now allocated sequentially.  This means that there will be a lot of hash collisions when
federation is in use.  We should use both block ID and block pool ID in {{hashCode}} to prevent
this.



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