Steve Loughran created MAPREDUCE-7282:
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Summary: MR v2 commit algorithm is dangerous, should be deprecated
and not the default
Key: MAPREDUCE-7282
URL: https://issues.apache.org/jira/browse/MAPREDUCE-7282
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: mrv2
Affects Versions: 3.1.3, 3.2.1, 3.3.0, 3.3.1
Reporter: Steve Loughran
The v2 MR commit algorithm moves files from the task attempt dir into the dest
dir on task commit -one by one
It is therefore not atomic
# if a task commit fails partway through and another task attempt commits
-unless exactly the same filenames are used, output of the first attempt may be
included in the final result
# if a worker partitions partway through task commit, and then continues after
another attempt has committed, it may partially overwrite the output -even when
the filenames are the same
Both MR and spark assume that task commits are atomic. Either they need to
consider that this is not the case, we add a way to probe for a committer
supporting atomic task commit, and the engines both add handling for task
commit failures (probably fail job)
Better: we remove this as the default, maybe also warn when it is being used
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