[jboss-as7-dev] HASingleton deployment

[Brian Stansberry]

Moving a discussion to the dev list.

Paul, using parallel operations instead of storing metadata with the 
deployment resource itself has a couple drawbacks:

1) On restart of the server the special handling information implicit in 
the parallel deployment ops is lost and the deployment becomes a 
non-singleton.

2) In a managed domain, the "special" operation can propagate to the 
relevant servers in the domain at the time it is invoked, but subsequent 
to that if another server is added to a server group that runs this 
deployment, again the special handling information is lost.

The stuff Thomas is working on that I mentioned is at 
https://github.com/jbossas/jboss-as/pull/2790.

On 9/12/12 12:17 AM, Paul Ferraro wrote:
> I did spend some time thinking about this last week while staring out at the Mediterranean Sea this past week.
> Fundamentally, implementing singleton deployments simply requires wrapping the corresponding Service<DeploymentUnit> in a SingletonService<DeploymentUnit>.  The effect is the deployment unit will be installed on all nodes in the cluster, but will start on only 1 node at a time.  The end result is more agile than what we had in EAP5, since we're only starting/stopping existing services, not creating them from from scratch.
>  From a domain model perspective, rather than tack on configuration meta data to the deployment resource itself, I think it would be simpler/cleaner to provide a parallel set of deploy/undeploy/redeploy operations.  The deploy/redeploy operations will accept additional optional parameters for cluster name and node preference (for a preferred node election policy).
> For standalone mode, it might still be nice to provide a separate file scanner using a distinct location that creates singleton deployments.  To clarify, this doesn't mean making the deployment scanner itself a singleton service, but rather the operations created by the scanner will install singleton deployment units instead of normal deployment units.
>
> Thoughts/comments?
>
> Paul
>
> ----- Original Message -----
>> From: "Brian Stansberry" <brian.stansberry at redhat.com>
>> To: "Paul Ferraro" <pferraro at redhat.com>
>> Sent: Wednesday, August 29, 2012 1:05:19 PM
>> Subject: HASingleton related issues in the EAP 6.1 PRD
>>
>> Care to comment on $subject at
>> https://docspace.corp.redhat.com/docs/DOC-105593 ?
>>
>> As I commented, I don't want to see an EAP 5-ish solution based on
>> activating a scanner when a node becomes master. That would be a
>> standalone-only hack. I think something along the lines of
>> associating
>> some configuration metadata with the deployment=* resource in the
>> management model makes more sense, and then some clustering
>> integration
>> to "(de)activate" the deployment.
>>
>> If you agree, we should chat about this a bit on the jboss-as7-dev
>> list
>> before you go. The "associating some configuration metadata with the
>> deployment=* resource" part intersects with some stuff Thomas Diesler
>> was trying to do, and the "activate the deployment" part intersects
>> with
>> some stuff Stuart Douglas was working on, as well as some OSGi stuff.
>>
>> --
>> Brian Stansberry
>> Principal Software Engineer
>> JBoss by Red Hat
>>


-- 
Brian Stansberry
Principal Software Engineer
JBoss by Red Hat