Rob Reeves created MAPREDUCE-7500:
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Summary: Support optimistic file renames in the commit protocol
Key: MAPREDUCE-7500
URL: https://issues.apache.org/jira/browse/MAPREDUCE-7500
Project: Hadoop Map/Reduce
Issue Type: Improvement
Components: client
Reporter: Rob Reeves
During a commit in FileOutputCommitter, every file commit checks if a file or
directory exists in the destination and if so deletes it before the rename. The
FileSystem.getFileStatus can take a significant amount of the total commit
time. However, the happy path is that no file exists in the destination so the
getFileStatus call is wasted time. The commit protocol can avoid this time by
optimistically assuming there is no file in the destination and only attempt to
delete it if the rename fails. In our HDFS environment this change reduced the
commit time by 70%.
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