[ClusterLabs] Colocation constraint moving resource

[Thomas Singleton]

Dear all

I am encountering an issue with colocation constraints. 

I have created a 4 nodes cluster (3 "main" and 1 "spare") with 3
resources and I wish to have each resource run only on its own node (or
on the spare) and resources must never run together on the spare.

I understand that this implies a definition of priorities between
resources should two nodes fail at the same time. This is the desired
behavior. Resource 1 is more important than resource 2 which is more
important than resource 3. And thus in the case of multiple nodes
failure, the spare node must be running the higher priority resource
even if this means the lower priority resources will be stopped.

When the resources are created with the adequate priorities but without
colocation constraint they are indeed running on each "main" node as
expected.

Trouble arises when I start adding the colocation constraints.

If I add one colocation constraint (resource3 cannot run with
resource2), resources remain correctly on their node. 

But as soon as I add a second colocation constraint (resource2 cannot
run with resource1), resource1 switches to the spare node because the
resource1 allocation score on node1 becomes -INFINITY and I cannot
understand why ?

Setup and commands output below

Thank you


****************

Resources definition, opt-in cluster

# pcs property set symmetric-cluster=false
# pcs resource create TestResourceNode1 ocf:pacemaker:Dummy op monitor
interval=120s
# pcs constraint location TestResourceNode1 prefers node1=100
# pcs constraint location TestResourceNode1 prefers nodespare=80
# pcs resource create TestResourceNode2 ocf:pacemaker:Dummy op monitor
interval=120s
# pcs constraint location TestResourceNode2 prefers node2=50
# pcs constraint location TestResourceNode2 prefers nodespare=30
# pcs resource create TestResourceNode3 ocf:pacemaker:Dummy op monitor
interval=120s
# pcs constraint location TestResourceNode3 prefers node3=10
# pcs constraint location TestResourceNode3 prefers nodespare=3

# crm_simulate -sL

Current cluster status:
Online: [ node1 node2 node3 nodespare ]

 TestResourceNode1	(ocf::pacemaker:Dummy):	Started node1
 TestResourceNode2	(ocf::pacemaker:Dummy):	Started node2
 TestResourceNode3	(ocf::pacemaker:Dummy):	Started node3

Allocation scores:
native_color: TestResourceNode1 allocation score on node1: 100
native_color: TestResourceNode1 allocation score on nodespare: 80
native_color: TestResourceNode2 allocation score on node2: 50
native_color: TestResourceNode2 allocation score on nodespare: 30
native_color: TestResourceNode3 allocation score on node3: 10
native_color: TestResourceNode3 allocation score on nodespare: 3

# pcs constraint colocation add TestResourceNode3 with
TestResourceNode2 score=-INFINITY
# crm_simulate -sL

Current cluster status:
Online: [ node1 node2 node3 nodespare ]

 TestResourceNode1	(ocf::pacemaker:Dummy):	Started node1
 TestResourceNode2	(ocf::pacemaker:Dummy):	Started node2
 TestResourceNode3	(ocf::pacemaker:Dummy):	Started node3

Allocation scores:
native_color: TestResourceNode1 allocation score on node1: 100
native_color: TestResourceNode1 allocation score on nodespare: 80
native_color: TestResourceNode2 allocation score on node2: 50
native_color: TestResourceNode2 allocation score on nodespare: 27
native_color: TestResourceNode3 allocation score on node3: 10
native_color: TestResourceNode3 allocation score on nodespare: 3

# pcs constraint colocation add TestResourceNode2 with
TestResourceNode1 score=-INFINITY
# crm_simulate -sL

Current cluster status:
Online: [ node1 node2 node3 nodespare ]

 TestResourceNode1	(ocf::pacemaker:Dummy):	Started
nodespare
 TestResourceNode2	(ocf::pacemaker:Dummy):	Started node2
 TestResourceNode3	(ocf::pacemaker:Dummy):	Started node3

Allocation scores:
native_color: TestResourceNode1 allocation score on node1: -INFINITY
native_color: TestResourceNode1 allocation score on nodespare: 53
native_color: TestResourceNode2 allocation score on node2: 50
native_color: TestResourceNode2 allocation score on nodespare:
-INFINITY
native_color: TestResourceNode3 allocation score on node3: 10
native_color: TestResourceNode3 allocation score on nodespare: 3





-- 
-------------------
Thomas Singleton
ACIC
singleton at acic.biz
+32 (0) 65 39 43 80