Am 2018-11-20 08:41, schrieb Michael Schwartzkopff:
Am 20.11.18 um 08:35 schrieb Bernd:
Am 2018-11-20 08:06, schrieb Ulrich Windl:
Bernd <be...@kroenchenstadt.de> schrieb am 20.11.2018 um 07:21 in
Nachricht
<dbae607c63168d4e14584abfba0b4...@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...? ;)
Regards,
Bernd
_______________________________________________
Users mailing list: Users@clusterlabs.org
https://lists.clusterlabs.org/mailman/listinfo/users
Project Home: http://www.clusterlabs.org
Getting started:
http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
Bugs: http://bugs.clusterlabs.org
hi,
I solved this problem years ago. I used the utilization attribute. But
you can use any attribute. You have to write an agent that measures the
CPU load every X minutes and updates the attribute. Now you just have
to add a location constraint, that starts the resource on the node with
the "best" attribute value. The "best" could be lowest CPU usage or
most
free RAM or whatever you want.
The disadvantage of this solution is that the cluster (i.e. pacemaker)
has to recalculate the scores every time you update your attribute.
That
causes additional load. If you have many resources the interdepend that
additional load may be not negligible.
Greetings,
Hi,
yes, that was my idea, too, see original post: Gathering the individual
nodes' load, and use Node Attributes (utilization) to help crmd to
decide where to put stuff.
As this would be the only resource of the cluster (all nodes otherwise
run a shared nothing approach) load would be no issue.
I built something like that in 2013, IIRC, but it was not pure cron – we
wrote a kind of wrapper (runner) as resource. That was a bit different.
Thanks for sharing!
Regards,
Bernd
_______________________________________________
Users mailing list: Users@clusterlabs.org
https://lists.clusterlabs.org/mailman/listinfo/users
Project Home: http://www.clusterlabs.org
Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
Bugs: http://bugs.clusterlabs.org
