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Date: Sat, 4 Jun 2011 04:46:47 +0000 (UTC)
From: "John George (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-1907) BlockMissingException upon
 concurrent read and write: reader was doing file position read while writer
 is doing write without hflush
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    [ https://issues.apache.org/jira/browse/HDFS-1907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13044199#comment-13044199 ] 

John George commented on HDFS-1907:
-----------------------------------

Filed HDFS-2034 to track this issue.

> BlockMissingException upon concurrent read and write: reader was doing file position read while writer is doing write without hflush
> ------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1907
>                 URL: https://issues.apache.org/jira/browse/HDFS-1907
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs client
>    Affects Versions: 0.23.0
>         Environment: Run on a real cluster. Using the latest 0.23 build.
>            Reporter: CW Chung
>            Assignee: John George
>             Fix For: 0.23.0
>
>         Attachments: HDFS-1907-2.patch, HDFS-1907-3.patch, HDFS-1907-4.patch, HDFS-1907-5.patch, HDFS-1907-5.patch, HDFS-1907.patch
>
>
> BlockMissingException is thrown under this test scenario:
> Two different processes doing concurrent file r/w: one read and the other write on the same file
>   - writer keep doing file write
>   - reader doing position file read from beginning of the file to the visible end of file, repeatedly
> The reader is basically doing:
>   byteRead = in.read(currentPosition, buffer, 0, byteToReadThisRound);
> where CurrentPostion=0, buffer is a byte array buffer, byteToReadThisRound = 1024*10000;
> Usually it does not fail right away. I have to read, close file, re-open the same file a few times to create the problem. I'll pose a test program to repro this problem after I've cleaned up a bit my current test program.

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