[ClusterLabs] trigger something at ?

[Ken Gaillot]

On Fri, 2024-01-26 at 13:55 +0100, lejeczek via Users wrote:
> Hi guys.
> 
> Is it possible to trigger some... action - I'm thinking specifically
> at shutdown/start.
> If not within the cluster then - if you do that - perhaps outside.
> I would like to create/remove constraints, when cluster starts &
> stops, respectively.
> 
> many thanks, L.
> 

You could use node status alerts for that, but it's risky for alert
agents to change the configuration (since that may result in more
alerts and potentially some sort of infinite loop).

Pacemaker has no concept of a full cluster start/stop, only node
start/stop. You could approximate that by checking whether the node
receiving the alert is the only active node.

Another possibility would be to write a resource agent that does what
you want and order everything else after it. However it's even more
risky for a resource agent to modify the configuration.

Finally you could write a systemd unit to do what you want and order it
after pacemaker.

What's wrong with leaving the constraints permanently configured?
-- 
Ken Gaillot <kgaillot at redhat.com>