Rolling updates

[Mark Eisenblätter]

hello list,

i' am using cf2 for quite a while and now starting with cf3, so my general knowledge is not to deep.

for my first project i will need rolling upgrades for a group of systems, if the service need to be restarted. 

installing new software/configurations is not the problem, and restarting when changes were made is ok.  

but how do i coordinate that only one(ore more) system is restarted at any time until all are finished.

thanks in advanced,

mark 

[Neil Watson]

I think using deterministic classes will help you distribute your
promises over a time window. Checkout dist and splayclass.

https://cfengine.com/docs/3.5/reference-functions-splayclass.html
https://cfengine.com/docs/3.5/reference-promise-types-classes.html#dist

You could also do it manually.

classes:
"batch" and => { "Hr10", hostrange("myhost_", "00-10") };
"batch" and => { "Hr11", hostrange("myhost_", "10-20") };

files:
batch::
"/myconfig.conf"
...
action => if_elapsed( "60" ),
classes => if_repaired( "restart_myservice" );

commands:
restart_myclass::
"/sbin/service restart myservice";

--
Neil H Watson
Promise Reporting with CFEngine Community http://evolvethinking.com/products/delta-reporting/
Make CFEngine simple with EFL http://evolvethinking.com/evolve-thinkings-free-cfengine-library/
VIM and Cfengine https://github.com/neilhwatson/vim_cf3

[Eisenblätter, Mark]

hi,

dist and splayclass looks good.

manually would be ok for a static setup, but we plan to use some scale up routines.

thanks for the help,

mark

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Grüße,

Mark Eisenblätter

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[Nick Anderson]

Also checkout the peers() function. With enterprise you could also use hostswithclass() and classesmatching to manage the coordination in a distributed way.

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[Aleksey Tsalolikhin]

Could you please provide an example of using hostswithclass() and classesmatching() to manage the coordination of a rolling upgrade?  Let's say I'm running "yum -y update-minimal --security && /sbin/reboot", and I only want one server per location to run it at a time?

I looked at https://docs.cfengine.com/latest/reference-functions-hostswithclass.html but didn't understand it.  Why is the policy hub editing a file? (Might help to add a comment to that files promise.)

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