[ https://issues.apache.org/jira/browse/MAPREDUCE-4892?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Bikas Saha updated MAPREDUCE-4892: ---------------------------------- Status: Patch Available (was: Open) > CombineFileInputFormat node input split can be skewed on small clusters > ----------------------------------------------------------------------- > > Key: MAPREDUCE-4892 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-4892 > Project: Hadoop Map/Reduce > Issue Type: Bug > Reporter: Bikas Saha > Assignee: Bikas Saha > Fix For: 3.0.0 > > Attachments: MAPREDUCE-4892.1.patch > > > The CombineFileInputFormat split generation logic tries to group blocks by > node in order to create splits. It iterates through the nodes and creates > splits on them until there aren't enough blocks left on a node that can be > grouped into a valid split. If the first few nodes have a lot of blocks on > them then they can end up getting a disproportionately large share of the > total number of splits created. This can result in poor locality of maps. > This problem is likely to happen on small clusters where its easier to create > a skew in the distribution of blocks on nodes. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira