Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Plain View
Hadoop >> mail # user >> Running map tasks after all reduces have finished

Jan Lukavský 2012-08-23, 09:25
Copy link to this message
Re: Running map tasks after all reduces have finished
Hey Jan,

What version/distribution of Hadoop are you noticing this on?

On Thu, Aug 23, 2012 at 2:55 PM, Jan Lukavský
> Hi all,
> we are seeing strange behaviour of JobTracker in the following scenario:
>  - job finishes map phase and starts reduce
>  - after the shuffle phase of all reducers we loose a tasktracker, that
> doesn't run any reducer - so all remaining reducers are still running in the
> reduce phase
>  - map tasks that were running on the lost tasktracker are rescheduled
>  - reduces may finish earlier than the rescheduled map tasks and so the job
> is blocked waiting for the maps to finish, although their output is simple
> discarded
> Is this behaviour a bug or feature? :) I haven't found any JIRA that would
> describe it, if there exists one can anyone point me out?
> Thanks,
>  Jan

Harsh J