Just a quick note... If your task is currently occupying a slot, the only way to release the slot is to kill the specific task. If you are using FS, you can move the task to another queue and/or you can lower the job's priority which will cause new tasks to spawn slower than other jobs so you will eventually free up the cluster.
There isn't a way to 'freeze' or stop a job mid state. Is the issue that the job has a large number of slots, or is it an issue of the individual tasks taking a long time to complete? If its the latter, you will probably want to go to a capacity scheduler over the fair scheduler. HTH -Mike On May 11, 2012, at 6:08 AM, Harsh J wrote: > I do not know about the per-host slot control (that is most likely not > supported, or not yet anyway - and perhaps feels wrong to do), but the > rest of the needs can be doable if you use schedulers and > queues/pools. > > If you use FairScheduler (FS), ensure that this job always goes to a > special pool and when you want to freeze the pool simply set the > pool's maxMaps and maxReduces to 0. Likewise, control max simultaneous > tasks as you wish, to constrict instead of freeze. When you make > changes to the FairScheduler configs, you do not need to restart the > JT, and you may simply wait a few seconds for FairScheduler to refresh > its own configs. > > More on FS at http://hadoop.apache.org/common/docs/current/fair_scheduler.html > > If you use CapacityScheduler (CS), then I believe you can do this by > again making sure the job goes to a specific queue, and when needed to > freeze it, simply set the queue's maximum-capacity to 0 (percentage) > or to constrict it, choose a lower, positive percentage value as you > need. You can also refresh CS to pick up config changes by refreshing > queues via mradmin. > > More on CS at > http://hadoop.apache.org/common/docs/current/capacity_scheduler.html > > Either approach will not freeze/constrict the job immediately, but > should certainly prevent it from progressing. Meaning, their existing > running tasks during the time of changes made to scheduler config will > continue to run till completion but further tasks scheduling from > those jobs shall begin seeing effect of the changes made. > > P.s. A better solution would be to make your job not take as many > days, somehow? :-) > > On Fri, May 11, 2012 at 4:13 PM, Rita <rmorgan...@gmail.com> wrote: >> I have a rather large map reduce job which takes few days. I was wondering >> if its possible for me to freeze the job or make the job less intensive. Is >> it possible to reduce the number of slots per host and then I can increase >> them overnight? >> >> >> tia >> >> -- >> --- Get your facts first, then you can distort them as you please.-- > > > > -- > Harsh J >
