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Luke Lu commented on MAPREDUCE-1521: ------------------------------------ 2a. Track output bytes per map and compute an extrapolated mapOutputBytes from a few randomly selected map output, so only a few maps needs to complete. We can have an expert mode to bypass the heuristic. > Protection against incorrectly configured reduces > ------------------------------------------------- > > Key: MAPREDUCE-1521 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-1521 > Project: Hadoop Map/Reduce > Issue Type: Improvement > Components: jobtracker > Reporter: Arun C Murthy > Assignee: Arun C Murthy > Priority: Critical > Fix For: 0.22.0 > > > We've seen a fair number of instances where naive users process huge > data-sets (>10TB) with badly mis-configured #reduces e.g. 1 reduce. > This is a significant problem on large clusters since it takes each attempt > of the reduce a long time to shuffle and then run into problems such as local > disk-space etc. Then it takes 4 such attempts. > Proposal: Come up with heuristics/configs to fail such jobs early. > Thoughts? -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.