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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-8760) Erasure Coding: reuse BlockReader when reading the same block in pread
Date Mon, 20 Jul 2015 19:04:05 GMT

     [ https://issues.apache.org/jira/browse/HDFS-8760?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jing Zhao updated HDFS-8760:
----------------------------
    Attachment: HDFS-8760-HDFS-7285.001.patch

Thanks for the review, Walter! Update the patch to address all your comments. 

In the meanwhile, {{testWriteReadUsingWebHdfs}} may fail after the change. The failure may
be related to HDFS-8797. So currently I temporarily disabled the pread test in {{testWriteReadUsingWebHdfs}}
and we can add it back later.

> Erasure Coding: reuse BlockReader when reading the same block in pread
> ----------------------------------------------------------------------
>
>                 Key: HDFS-8760
>                 URL: https://issues.apache.org/jira/browse/HDFS-8760
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Jing Zhao
>            Assignee: Jing Zhao
>         Attachments: HDFS-8760-HDFS-7285.001.patch, HDFS-8760.000.patch
>
>
> Currently in pread, we create a new block reader for each aligned stripe even though
these stripes belong to the same block. It's better to reuse them to avoid unnecessary block
reader creation overhead. This can also avoid reading from the same bad DataNode.



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