[ClusterLabs] trigger something at ?

[lejeczek]

On 29/01/2024 17:22, Ken Gaillot wrote:
> 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?
yes, that would be for a node start/stop
I struggle with using constraints to move pgsql (PAF) master 
onto a given node - seems that co/locating paf's master 
results in troubles (replication brakes) at/after node 
shutdown/reboot (not always, but way too often)

Ideally I'm hoping that:
at node stop, stopping node could check if it's PAF's master 
and if yes so then remove given constraints