Let's say I have these requirements:
- a master/slave resource called res-a
- a normal resource called res-b that runs on node1 only
- a normal resource called res-c that runs on node2 only
- res-b and res-c both do the same thing, but they are configured as
separate resources so I can refer to each individually
- res-a must be started before res-b or res-c start
- res-a can only be promoted to Master on node1 if res-b is running
- res-a can only be promoted to Master on node2 if res-c is running
- res-a prefers node1 to be Master
- If res-a is Master on node1 and res-b fails, res-a should move to
node2 if res-c is running
- If res-a is Master on node2 and res-c fails, res-a should move to
node1 if res-b is running
How would I set up the constraints?
This should make res-a prefer node1 over node2, but allow res-a to fail over to
node2:
<rsc_location id="res-a-location" rsc="res-a">
<rule id="res-a-location-rule-1" score="500">
<expression id="res-a-location-rule-1-exp" attribute="#uname"
operation="eq" value="node1"/>
</rule>
<rule id="res-a-location-rule-2" score="0">
<expression id="res-a-location-rule-2-exp" attribute="#uname"
operation="eq" value="node2"/>
</rule>
</rsc_location>
This should make res-b run only on node1:
<rsc_location id="res-b-location" rsc="res-b">
<rule id="res-b-location-rule-1" score="INFINITY">
<expression id="res-b-location-rule-1-exp" attribute="#uname"
operation="eq" value="node1"/>
</rule>
<rule id="res-b-location-rule-2" score="-INFINITY">
<expression id="res-b-location-rule-2-exp" attribute="#uname"
operation="eq" value="node2"/>
</rule>
</rsc_location>
This should make res-c run only on node2:
<rsc_location id="res-c-location" rsc="res-c">
<rule id="res-c-location-rule-1" score="-INFINITY">
<expression id="res-c-location-rule-1-exp" attribute="#uname"
operation="eq" value="node1"/>
</rule>
<rule id="res-c-location-rule-2" score="INFINITY">
<expression id="res-c-location-rule-2-exp" attribute="#uname"
operation="eq" value="node2"/>
</rule>
</rsc_location>
This should make res-a start before res-b starts:
<rsc_order id="order-res-a-first-then-b">
<resource_set id="res-a-set-1" sequential="true">
<resource_ref id="res-a"/>
</resource_set>
<resource_set id="res-b-set" sequential="false">
<resource_ref id="res-b"/>
</resource_set>
</rsc_order>
This should make res-a start before res-c starts:
<rsc_order id="order-res-a-first-then-c">
<resource_set id="res-a-set-2" sequential="true">
<resource_ref id="res-a"/>
</resource_set>
<resource_set id="res-c-set" sequential="false">
<resource_ref id="res-c"/>
</resource_set>
</rsc_order>
This should make res-a only run as Master on node1 if res-b is started and make
it prefer node1:
<rsc_colocation id="res-a-prefers-node1" score="500">
<resource_set id="res-a-prefers-node1-set-1" role="Master">
<resource_ref id="res-a"/>
</resource_set>
<resource_set id="res-a-prefers-node1-set-2" role="Started">
<resource_ref id="res-b"/>
</resource_set>
</rsc_colocation>
This should make res-a only run as Master on node1 if res-c is started and make
it not prefer node2:
<rsc_colocation id="res-a-not-prefer-node2" score="250">
<resource_set id="res-a-not-prefer-node2-set-1" role="Master">
<resource_ref id="res-a"/>
</resource_set>
<resource_set id="res-a-not-prefer-node2-set-2" role="Started">
<resource_ref id="res-c"/>
</resource_set>
</rsc_colocation>
I do see res-a starting before b and c, and I do see it being promoted to
master on node1. I also see res-b starting on node1 only and res-c on node2
only.
However, based on these constraints, I would expect that if I forced res-b to
fail when res-a is Master on node1, then res-a should switch to Master on
node2. Once that is done, then I would expect res-b to restart on node1 and
res-a to stay Master on node2 (because of stickiness).
Instead, if I cause res-b to fail, it simply restarts res-b. Is there something
I am missing in this logic? Do I need another constraint to force it over to
node2 if res-b fails? Do I need another constraint to force it to node1 if
res-c fails on node2?
Thanks for any assistance you can provide.
Eliot Gable
Senior Engineer
1228 Euclid Ave, Suite 390
Cleveland, OH 44115
Direct: 216-373-4808
Fax: 216-373-4657
ega...@broadvox.net<mailto:ega...@broadvox.net>
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