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From "Yoram Arnon (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-508) random seeks using FSDataInputStream can become invalid such that reads return invalid data
Date Tue, 05 Sep 2006 21:27:23 GMT
     [ http://issues.apache.org/jira/browse/HADOOP-508?page=all ]

Yoram Arnon updated HADOOP-508:
-------------------------------

    Component/s: dfs

> random seeks using FSDataInputStream can become invalid such that reads return invalid
data
> -------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-508
>                 URL: http://issues.apache.org/jira/browse/HADOOP-508
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.5.0
>            Reporter: Christian Kunz
>
> Some of my applications using Hadoop DFS  receive wrong data after certain random seeks.
After some investigation I believe (without looking at source code of java.io.BufferedInputStream)
that it basically boils down to the fact that the method 
> read(byte[] b, int off, int len), when called with an external buffer larger than the
internal buffer, reads into the external buffer directly without using the internal buffer
anymore, but without invalidating the internal buffer by setting the variable 'count' to 0
such that a subsequent seek to an offset which is closer to the 'position' of the Positioncache
than the internal buffersize will put the current position into the internal buffer containing
outdated data from somewhere else.

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