[ https://issues.apache.org/jira/browse/MAPREDUCE-4772?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Robert Joseph Evans updated MAPREDUCE-4772: ------------------------------------------- Priority: Major (was: Critical) > Fetch failures can take way too long for a map to be restarted > -------------------------------------------------------------- > > Key: MAPREDUCE-4772 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-4772 > Project: Hadoop Map/Reduce > Issue Type: Bug > Components: mrv2 > Affects Versions: 0.23.4 > Reporter: Robert Joseph Evans > Assignee: Robert Joseph Evans > > In one particular case we saw a NM go down at just the right time, that most > of the reducers got the output of the map tasks, but not all of them. > The ones that failed to get the output reported to the AM rather quickly that > they could not fetch from the NM, but because the other reducers were still > running the AM would not relaunch the map task because there weren't more > than 50% of the running reducers that had reported fetch failures. Then > because of the exponential back-off for fetches on the reducers it took until > 1 hour 45 min for the reduce tasks to hit another 10 fetch failures and > report in again. At that point the other reducers had finished and the job > relaunched the map task. If the reducers had still been running at 1:45 I > have no idea how long it would have taken for each of the tasks to get to 30 > fetch failures. > We need to trigger the map based off of percentage of reducers shuffling, not > percentage of reducers running, we also need to have a maximum limit of the > back off, so that we don't ever have the reducer waiting for days to try and > fetch map output. -- 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