[ClusterLabs] Question about ping nodes

[Andrei Borzenkov]

On 18.04.2021 08:41, Andrei Borzenkov wrote:
> On 17.04.2021 22:41, Piotr Kandziora wrote:
>> Hi,
>>
>> Hope some guru will advise here ;)
>>
>> I've got two nodes cluster with some resource placement dependent on ping
>> node visibility (
>> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/high_availability_add-on_reference/s1-moving_resources_due_to_connectivity_changes-haar
>> ).
>>
>> Is it possible to do nothing with these resources when both nodes do not
>> have access to the ping node?
>>
>> Currently, when the ping node is unavailable (node itself becomes
>> unavailable) both nodes stop the resources.
>>
> 
> Just use any negative score higher than -INFINITY in location constraint.
> 

No, it does not work. I was mislead by documentation (5.2.1 location
properties):

score:

Negative values indicate the resource(s) should avoid this node (a value
of -INFINITY changes "should" to "must").

I interpreted "should" as "pacemaker will normally avoid this node but
still may chose it if nothing better is possible". It is not what
happens. Apparently negative score completely prevents assigning
resource to this node, and "should" here probably means "it is still
possible that final score may become positive".

As it is not possible to refer to attributes of multiple nodes in a
rule, you would need something that combines current pingd status for
individual nodes and makes it available. Logical place is
ocf:pacemaker:ping resource agent itself.