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Vinod Kumar Vavilapalli commented on MAPREDUCE-3749: ---------------------------------------------------- Tom, FYI, we found that the extra copy is indeed a problem as we ran into performance issues while running benchmarks. I created MAPREDUCE-3827 to instead use a Concurrent HashMap and give a fail-safe weakly consistent iterator. > ConcurrentModificationException in counter groups > ------------------------------------------------- > > Key: MAPREDUCE-3749 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-3749 > Project: Hadoop Map/Reduce > Issue Type: Bug > Components: mrv2 > Affects Versions: 0.23.0 > Reporter: Tom White > Assignee: Tom White > Priority: Blocker > Fix For: 0.23.1 > > Attachments: MAPREDUCE-3749-concurrent.patch, > MAPREDUCE-3749-test.patch, MAPREDUCE-3749.patch, MAPREDUCE-3749.patch > > > Iterating over a counter's groups while adding more groups will cause a > ConcurrentModificationException. > This was found while running Hive unit tests against a recent 0.23 version. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira