[ https://issues.apache.org/jira/browse/MAPREDUCE-6485?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Xianyin Xin reassigned MAPREDUCE-6485: -------------------------------------- Assignee: Xianyin Xin > MR job hanged forever because all resources are taken up by reducers and the > last map attempt never get resource to run > ----------------------------------------------------------------------------------------------------------------------- > > Key: MAPREDUCE-6485 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-6485 > Project: Hadoop Map/Reduce > Issue Type: Bug > Components: applicationmaster > Affects Versions: 3.0.0, 2.4.1, 2.6.0, 2.7.1 > Reporter: Bob > Assignee: Xianyin Xin > Priority: Critical > Attachments: MAPREDUCE-6485.001.patch > > > The scenarios is like this: > With configuring mapreduce.job.reduce.slowstart.completedmaps=0.8, reduces > will take resource and start to run when all the map have not finished. > But It could happened that when all the resources are taken up by running > reduces, there is still one map not finished. > Under this condition , the last map have two task attempts . > As for the first attempt was killed due to timeout(mapreduce.task.timeout), > and its state transitioned from RUNNING to FAIL_CONTAINER_CLEANUP, so failed > map attempt would not be started. > As for the second attempt which was started due to having enable map task > speculative is pending at UNASSINGED state because of no resource available. > But the second map attempt request have lower priority than reduces, so > preemption would not happened. > As a result all reduces would not finished because of there is one map left. > and the last map hanged there because of no resource available. so, the job > would never finish. -- This message was sent by Atlassian JIRA (v6.3.4#6332)