[Pacemaker] Make resources more important than others

[Luke Bigum]

On 21/06/11 13:41, Dejan Muhamedagic wrote:
> Hi,
>
> On Thu, Jun 02, 2011 at 08:44:46AM +0100, Luke Bigum wrote:
>> 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.
> You were (most probably) right :)
>
> But it sounds interesting. Now, if java is not so important, why
> do you run it in the cluster?
>
> Thanks,
>
> Dejan

Very good question :) The Java is our in-house software deployment agent 
in which we also deploy MySQL, as well as our own code.  At design time 
it was easier to add our Java agent to Pacemaker rather than code 
cluster awareness into it. Unfortunately that decision was bitten us a 
few too many times now in various ways, including the chicken and egg 
situation where the Java agent needs to be able to control the cluster 
(unmanage MySQL to upgrade it) and is itself controlled by the cluster. 
Our way forward now is to code Pacemaker awareness into our agent and 
run it on every node.

-Luke

>> 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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>>
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-- 
Luke Bigum

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


The information in this e-mail and any attachment is confidential and is intended only for the named recipient(s). The e-mail may not be disclosed or used by any person other than the addressee, nor may it be copied in any way. If you are not a named recipient please notify the sender immediately and delete any copies of this message. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. Any view or opinions presented are solely those of the author and do not necessarily represent those of the company.