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Karthik Kambatla commented on MAPREDUCE-5110: --------------------------------------------- Thanks for your response, Arun. Let me take a step back and explain in detail: AIC the issue this JIRA address is - "Where possible (i.e., not transient network partitions), run a single task attempt for a task when speculation is turned off". A JT solution (a.k.a MAPREDUCE-2217) spawns another task attempt, but doesn't kill the currently running task before doing so. Through a TT-side solution (patch here), one will be able to kill the currently running attempt first before spawning another task attempt. I see your point of avoid-TT-changes-if-possible. I guess the trade-off is between marginal increase in TT code complexity (a timeout check and logging changes) and running multiple attempts of the task. Given the low cost of the fix, I believe we should address this scenario which seems to be far more frequent compared to network partitions. > Long task launch delays can lead to multiple parallel attempts of the task > -------------------------------------------------------------------------- > > Key: MAPREDUCE-5110 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-5110 > Project: Hadoop Map/Reduce > Issue Type: Bug > Components: tasktracker > Affects Versions: 1.1.2 > Reporter: Karthik Kambatla > Assignee: Karthik Kambatla > Attachments: expose-mr-5110.patch, mr-5110.patch, mr-5110.patch, > mr-5110-tt-only.patch > > > If a task takes too long to launch, the JT expires the task and schedules > another attempt. The earlier attempt can start after the later attempt > leading to two parallel attempts running at the same time. This is > particularly an issue if the user turns off speculation and expects a single > attempt of a task to run at any point in time. -- 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