[Linux-cluster] Re: Resource configuration syntax for cluster.conf

[Lon Hohberger]

On Wed, 2009-05-20 at 19:08 +0530, Mrugesh Karnik wrote:
> Hi,
> 
> I have few questions about the exact syntax for configuring resources managed 
> by rgmanager in cluster.conf.
> 
> * It seems like the vm resource agent can be configured directly under <rm/>. 
> Is there a specific schema or such to figure out which resource agents can be 
> configured this way, without using <resources/> or <service/>? 

*Technically*, they all can, but it's not terribly useful and becomes
very complicated to track very quickly:

  <rm>
    <ip address="1.2.3.4" />
  </rm>

... lets you do:

  clusvcadm -[edRr] ip:1.2.3.4

:o

Only <vm> and <service> support adding policies (failover domains, etc.)
to them.

This method of operation isn't really supported since rgmanager doesn't
have a proper dependency engine.


> It turns out that Live Migration of the VMs with clusvcadm -M does 
> not work if the vm resource is specified under a resource tree.

Correct.  This is because there are implied dependencies in the tree,
and not all resources can be live-migrated (in fact... only <vm> can
right now).  So, you can only migrate a VM if it has no dependencies and
is dependent on nothing (for now).


> * The meta-data for a resource lists various <action/> values. Are these 
> configurable? If yes, how do I configure these? Do they go in as a child tag 
> for the specific resource configured under a resource tree?

You can configure them in cluster.conf using the special <action>
child[1]:

   <service> 
     <ip ... >
       <action name="status" interval="60" depth="*"/>
     </ip>
     ...
   </service>

Or if you were using a vm...

   <vm ...>
     <action name="status" interval="60" depth="*"/>
   </vm>

It's an ugly "special case".  It was added a couple of years after we
started using the resource tree setup :/

> 
> * What is the meaning of the <special/> tag output by the meta-data?

Resource-manager specific stuff.  rgmanager has things that give it
hints about when to 'stop' resources and child-type ordering, as well as
the maximum number of times a resource can be started (it's either '1'
or 'unset' right now).  There used to be hints about whether a resource
could appear at the top level (attributes/@root="1"), but that's been
unused since the RHEL4/STABLE branch.

Child-type ordering is reasonably documented:

http://sources.redhat.com/cluster/wiki/ResourceTrees

-- Lon

1. That means that you can't define a resource type called "action".  I
don't know what would happen if you did ;)