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From "James Clampffer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9103) Retry reads on DN failure
Date Mon, 21 Sep 2015 19:12:04 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14901213#comment-14901213
] 

James Clampffer commented on HDFS-9103:
---------------------------------------

I agree with Bob that the C++ API should be reasonably usable on its own; it might not be
tuned perfectly but that could be added incrementally on the user side.  We could supply callback(s)
to handle different sorts of failures later, something like InputStream::onDroppedConnection.
 The InputStream will still handle the failure it but it allows a user to see what's going
on.

Just to be safe it might be worth wrapping previously_excluded_datanodes in a lock.  Or we
should agree on threading semantics that say it doesn't need one there.
Otherwise +1



> Retry reads on DN failure
> -------------------------
>
>                 Key: HDFS-9103
>                 URL: https://issues.apache.org/jira/browse/HDFS-9103
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client
>            Reporter: Bob Hansen
>            Assignee: Bob Hansen
>             Fix For: HDFS-8707
>
>         Attachments: HDFS-9103.1.patch, HDFS-9103.2.patch
>
>
> When AsyncPreadSome fails, add the failed DataNode to the excluded list and try again.



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