[ClusterLabs] Antw: Placing resource based on least load on a node

Bernd bernd at kroenchenstadt.de
Tue Nov 20 02:35:26 EST 2018

Am 2018-11-20 08:06, schrieb Ulrich Windl:
>>>> Bernd <bernd at kroenchenstadt.de> schrieb am 20.11.2018 um 07:21 in 
>>>> Nachricht
> <dbae607c63168d4e14584abfba0b4b1b at kroenchenstadt.de>:
>> Hi,
>> I'd like to run a certain bunch of cronjobs from time to time on the
>> cluster node (four node cluster) that has the lowest load of all four
>> nodes.
>> The parameters wanted for this system yet to build are
>> * automatic placement on one of the four nodes (i.e., that with the
>> lowest load)
>> * in case a node fails, automatically removed from the cluster
>> * it must only exist a single entity of the cronjob entity running
>> so this really screams for pacemakter being used as foundation.
>> However, I'm not sure how to implement the "put onto node with least
>> load" part. I was thinking to use Node Attributes for that, but I 
>> didn't
>> find any solution "out of the box" for this. Furthermore, as load is a
>> highly volatile value, how can one make sure that all cronjobs are run
>> to the end without being moved to a node that possibly meanwhile got a
>> lower load than the one executing the jobs?
> Hi!
> Actually I think the last one is the easiest (assuming the cron jobs
> do not need any resources that are moved): Once a cron job is started,
> it will run until it ends, whether it's crontab has been moved or not.
> Despite of that I think cluster software is not ideal when you
> actually need load-balancing software.
> Regards,
> Ulrich

The only resource(s) existing would be the cron "runner".

The point about load balancing is true, yes... so, any idea what to use 
instead? Is there already a tool or framework for solving a problem like 
this available or do I have to start from scratch? Not that I'd be too 
lazy, but what's the use of reinventing the wheel repeatedly...? ;)



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