[Pacemaker] Make resources more important than others

[Luke Bigum]

Hi list,

I have a conceptual question about making Pacemaker treat some resources 
a lot more important than others. I'm afraid the answer is going to come 
back "sorry you can't", but I just want to confirm.

I have a simple 2 node cluster that runs two services (MySQL and a Java 
daemon) on top of network attached storage that can float between both 
nodes. CRM config looks a bit like:

node node1
node node2
primitive lsb:mysql mysql
primitive lsb:java java
primitve lsb:storage storage
colocation mysql_with_storage inf: mysql storage
colocation java_with_storage inf: java storage
order mysql_after_storage: storage:start mysql:start symmetrical=true
order java_after_storage: storage:start java:start symmetrical=true

I've got the interesting requirement that mysql is vastly more important 
than the java resource. The java has to run on the same server as mysql. 
Also, if mysql is stopped/unmanaged, the java should still be running on 
what would be the correct node for mysql. I've mostly achieved this by 
colocating the java and mysql to the underlying storage.

It gets tricky when we start simulating hard failures. If we simulate a 
hard error with mysql, the storage moves to another node, then mysql and 
java, and everything's great. What I don't want is the opposite to 
occur. I don't want any hard error with java to make the mysql move, as 
I consider the mysql more important than java and I don't want to outage 
mysql if the java has a problem. I'd love for the mysql to stay running 
  where it is and have an administrator come along and cleanup what's 
wrong with the java.

I guess I want to somehow describe the java resource as "not as 
important" as mysql, and this is what I don't think is possible. I know 
I'm talking about very edge cases by simulating hard errors (eg: monitor 
return code 5), but it'd be nice to achieve.

Any thoughts?

Thanks in advance,

-Luke

-- 
Luke Bigum

Information Systems
Luke.Bigum at lmax.com | http://www.lmax.com
LMAX, Yellow Building, 1A Nicholas Road, London W11 4AN


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