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
