jay vyas created MAPREDUCE-5572:
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Summary: Provide alternative logic for getPos() implementation in
custom RecordReader
Key: MAPREDUCE-5572
URL: https://issues.apache.org/jira/browse/MAPREDUCE-5572
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: examples
Affects Versions: 1.2.1, 1.2.0, 1.1.1, 1.1.0, 1.1.3, 1.2.2
Reporter: jay vyas
Priority: Minor
The custom RecordReader class defines the getPos() as follows:
long currentOffset = currentStream == null ? 0 : currentStream.getPos();
...
This is meant to prevent errors when underlying stream is null. But it doesn't
gaurantee to work: The RawLocalFileSystem, for example, currectly will close
the underlying file stream once it is consumed, and the currentStream will thus
throw a NullPointerException when trying to access the null stream.
This is only seen when running this in the context where the MapTask class,
which is only relevant in mapred.* API, calls getPos() twice in tandem, before
and after reading a record.
This custom record reader should be gaurded, or else eliminated, since it
assumes something which is not in the FileSystem contract: That a getPos will
always return a integral value.
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