random seeks using FSDataInputStream can become invalid such that reads return
invalid data
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Key: HADOOP-508
URL: http://issues.apache.org/jira/browse/HADOOP-508
Project: Hadoop
Issue Type: Bug
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outdated data from somewhere else.
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