[ClusterLabs] Colocation rule with vip and ms master

[Andrei Borzenkov]

26.10.2017 21:15, Norberto Lopes пишет:
> Hi everyone,
> 
> Could someone give me a bit more in-depth explanation of the semantical
> differences between the following:
> 
> (assume postgresMS is a master/slave resource for postgresql)
> (ignore for a moment that the first rule could put the vip in the 3rd
> [Started] node)
> 
> colocation backup-vip-not-with-master -inf: backupVIP postgresMS:Master
> colocation backup-vip-not-with-master inf: backupVIP postgresMS:Slave
> 
> Basically what's occurring in my cluster is that the first rule stops the
> Sync node from being promoted if the Master ever dies. The second doesn't
> but I can't quite follow why.
> 
> Any ideas?
> 

Note that placement decision for posgtresMS:Mater will include score of
backupVIP. As it is mandatory placement, final score for any node will
be score(postgresMS:Master) - score(backupVIP). So it can result in
negative total, prohibiting placement of postgresMS:Master. Another
constraint does not have this problem as a) placement of
postrgresMS:Mater is indepndent of backupVIP and b) scores only add up.