Jason Lowe created TEZ-3103:
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Summary: Shuffle can hang when memory to memory merging enabled
Key: TEZ-3103
URL: https://issues.apache.org/jira/browse/TEZ-3103
Project: Apache Tez
Issue Type: Bug
Affects Versions: 0.7.0
Reporter: Jason Lowe
Assignee: Jason Lowe
Priority: Critical
The shuffle process can hang when memory to memory merging is enabled. As the
memory-to-memory merge progresses it closes out the input segments which in
turn lowers the commitMemory associated with those segments. However when the
merge completes it fails to increase the commitMemory accordingly for the
resulting merged segment. This effectively "leaks" shuffle memory, and we can
end up in a situation where there's insufficient memory to perform any more
in-memory shuffles but commitMemory is too low to trigger a merge. All the
fetcher threads eventually end up waiting on the merge that will never occur,
and the shuffle hangs.
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