[ClusterLabs] Pacemaker alert framework

[Klaus Wenninger]

On 07/06/2018 03:41 PM, Ian Underhill wrote:
> requirement:
> when a resource fails perform an actionm, run a script on all nodes
> within the cluster, before the resource is relocated. i.e. information
> gathering why the resource failed.

Have in mind that trying to run a script on all nodes in the cluster before
proceeding is a delicate issue because not being able to run it on one
node might prevent relocation and thus availability.
Of course this largely depends on how it is implemented - just wanted
to raise attention.
 
>
> what I have looked into:
> 1) Use the monitor call within the resource to SSH to all nodes, again
> SSH config needed.
> 2) Alert framework : this only seems to be triggered for nodes
> involved in the relocation of the resource. i.e. if resource moves
> from node1 to node 2 node 3 doesnt know. so back to the SSH solution :(

Alerts are designed not to block anything (no other alerts as well) so
the alert-agents are
just called on nodes that anyway already have to do with that very event.

> 3) sending a custom alert to all nodes in the cluster? is this
> possible? not found a way?
>
> only solution I have:
> 1) use SSH within an alert monitor (stop) to SSH onto all nodes to
> perform the action, the nodes could be configured using the alert
> monitors recipients, but I would still need to config SSH users and
> certs etc.
>      1.a) this doesnt seem to be usable if the resource is relocated
> back to the same node, as the alerts start\stop are run at the "same
> time". i.e I need to delay the start till the SSH has completed.
>
> what I would like:
> 1) delay the start\relocation of the resource until the information
> from all nodes is complete, using only pacemaker behaviour\config
>
> any ideas?

Not 100% sure of what what your exact intention is ...
You could experiment with a clone that depends on the running instance and
use the stop of that to trigger whatever you need.
Not sure but I'd expect that pacemaker would tear down all clone instances
before it relocates your resource.

Regards,
Klaus

>
> Thanks
>
> /Ian.
>
>
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