Race in shuffle can cause it to hang
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Key: MAPREDUCE-3721
URL: https://issues.apache.org/jira/browse/MAPREDUCE-3721
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: mrv2
Affects Versions: 0.23.0
Reporter: Siddharth Seth
Assignee: Siddharth Seth
Priority: Blocker
If all current {{Fetcher}}s complete while an in-memory merge is in progress -
shuffle could hang.
Specifically - if the memory freed by an in-memory merge does not bring
{{MergeManager.usedMemory}} below {{MergeManager.memoryLimit}} and all current
Fetchers complete before the in-memory merge completes, another in-memory merge
will not be triggered - and shuffle will hang. (All new fetchers are asked to
WAIT).
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