6

Using pacemaker in a 2 nodes master/slave configuration.
In order to perform some tests, we want to switch the master role from node1 to node2, and vice-versa. For instance if the current master is node1, doing

# crm resource migrate r0 node2

does indeed move the resource to node2. Then, ideally,

# crm resource migrate r0 node1

would migrate back to node1. The problem is that migrate added a line in the configuration to perform the switch

location cli-prefer-r0 r0 role=Started inf: node2

and in order to migrate back I have first to remove that line...

Is there a better way to switch master from one node to the other?

  • Have you tried moving the resource instead of migrating? – YoMismo Dec 2 '14 at 9:56
  • Do you have active/active or active/passive setup? if it is active/active you can just bring one node to standby and check if the resources are moved to the other node. – YoMismo Dec 2 '14 at 10:26
  • @YoMismo Active/passive. What is the difference between migrate and move? – Ring Ø Dec 2 '14 at 23:44
  • It's been a long time since I had my cluster running, I've been checking crm's man page and migrate/move appear to be equivalent, but clusterlabs.org/doc/en-US/Pacemaker/1.1-plugin/html/… uses moving instead of migrating, for documentation I would use clusterlabs, since it is (or was when I set my cluster up) project's main page. If you have active/passive then it is easy for you, activate the second node and put in standby the first one, resources will have to move automatically. Have you checked the documentation? clusterlabs.org/doc – YoMismo Dec 3 '14 at 10:08
4

I know this bit old; but it seems like no one answered this satisfactorily, and the requester never posted if his problem was solved or not. So here is an explanation.

When you perform:

# crm resource migrate r0 node2

a cli-prefer-* rule is created.

Now when you want to move the r0 back to node1, you don't do:

# crm resource migrate r0 node1

but you perform:

# crm resource unmigrate r0

Using umigrate or unmove gets rid of the cli-prefer-* rule automatically.

If you try to delete this rule manually in cluster config, really bad things happen in cluster, or at least bad things happened in my case.

  • I know this is quite old, but what "bad things" happened when you deleted the rule? Does using "unmigrate" move the resource to another node, or just cleanly remove the prefer rules? – Michael Firth Jul 16 '18 at 10:40
  • Unmigrate removes the location constraint that is keeping a given resource from running on the "migrated from" node - it does not perform any move operations of its own, but just make them possible. If a resource has a preference for that node, it will try to move back if ordering/collocation constraints allow the resource to do so. – Spooler Aug 16 '18 at 21:48

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