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From Shi Yu <sh...@uchicago.edu>
Subject Re: freeze a mapreduce job
Date Fri, 11 May 2012 14:03:57 GMT
Is there any risk to suppress a job too long in FS?    I guess there are 
some parameters to control the waiting time of a job (such as timeout 
,etc.),   for example, if a job is kept idle for more than 24 hours is 
there a configuration deciding kill/keep that job?


On 5/11/2012 6:52 AM, Rita wrote:
> thanks.  I think I will investigate capacity scheduler.
> On Fri, May 11, 2012 at 7:26 AM, Michael Segel<michael_segel@hotmail.com>wrote:
>> 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<rmorgan466@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

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