[ClusterLabs] Colocation per site ?

[Ken Gaillot]

On Wed, 2021-02-17 at 16:46 +0000, Strahil Nikolov wrote:
> Hello All,
> 
> I'm currently in a process of building SAP HANA Scale-out cluster and
> the HANA team has asked that all nodes on the active instance should
> have one IP for backup purposes.
> 
> Yet, I'm not sure how to setup the constraints (if it is possible at
> all) so all IPs will follow the master resource and yet run on a
> separate host.
> 
> I know that I can set location constraints between each pair of nodes
> , but the logic identifying the master's DC is eluding me.
> 
> Best Regards,
> Strahil Nikolov

If I understand you correctly, you have some nodes at one site, and
other nodes at a different site, and you want all resources to be on
the same site but not necessarily the same nodes.

There is a rarely used feature exactly for this: colocation by node
attribute. You can set a node attribute (e.g. "site" = "1" or "2") for
each node, then colocate the IPs with the master role using the site
node attribute. See:

https://clusterlabs.org/pacemaker/doc/en-US/Pacemaker/2.0/html-single/Pacemaker_Explained/index.html#s-coloc-attribute
-- 
Ken Gaillot <kgaillot at redhat.com>