[Pacemaker] master/slave or unique clones

[Florian Haas]

On 2010-05-28 14:20, Vadym Chepkov wrote:
> 
> On May 28, 2010, at 8:12 AM, Florian Haas wrote:
> 
>> On 2010-05-28 14:01, Vadym Chepkov wrote:
>>> Hi,
>>>
>>> I want to convert our home-made application to be managed by pacemaker cluster. 
>>> The way it works now: application starts, discovers all IPs configured on the system and if it sees preconfigured IP it becomes "master" and will serve configuration requests, 
>>> if not - "node" and will try to connect to "master" node to get configuration data. Other then that, application instances are absolutely the same on all "cluster" servers and 
>>> they start collecting their own unique data.
>>>
>>> I started to write a resource agent in "stateful" manner, but the problem is - I can't promote or demote and the documentation says : application has to start in "slave" mode, 
>>> which I can't supply. So I thought of unique clones instead, but I need to create collocation/ordering constraint with IP for the clone:0 and again documentation says I shouldn't do it.
>>>
>>> As a workaround I could probably create a separate "master" instance and clones with clone-max=node-1 and create -INFINITY collocation constraint between them, but it's more of a hack it seems.
>>
>> Show us your RA and I'm sure quite a few people will come up with
>> helpful suggestions.
>>
> 
> Imperative word was "started". You think I still should go multi-state RA for this application?

If the application which that RA applies to distinguishes between roles
equivalent to a Master and a Slave, and you want the RA to manage those,
then probably yes.

What makes you think you can't start the RA in Slave mode?

Florian

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