[mod_cluster-dev] Enabling mod_cluster by default in AS6

[Paul Ferraro]

On Tue, 2010-05-04 at 09:57 +0200, Bela Ban wrote:
> Paul Ferraro wrote:

<snip>

> TBH, I'm not a 100% sure what the code above does... is it adding a 
> lifecycle listener dynamically if mod_cluster is started after JBossWeb 
> ? Actually, I guess this will always be the case as you have a 
> dependency from mod-cluster to JBossWeb.

In summary, if the jbossweb server exists that means the WebServer
service was already started.  If this is the case, then dynamically add
the mod_cluster lifecycle listener, and trigger the init and start
events manually (since those events were missed).

> > This requires a small modification to the
> > MicrocontainerIntegrationLifecycleListener, which will need to delegate
> > equals(Object) to its non-null delegate listener if the argument is a
> > LifecycleListener, but not an instanceof MCILL.
> >
> > So, this essentially does what you described. There are couple other
> > advantages:
> > 1. We no longer need to define a <Listener/> in server.xml (closes 
> > MODCLUSTER-20 !!!).
> 
> Because you're adding the listener dynamically, a la MODCLUSTER-20, right ?

Right.

> Wow, that would be great !
> 
> > 2. We no longer rely on the finicky 
> > MicrocontainerIntegrationLifecycleListener, which requires (so to avoid
> > a call to JBossWebMicrocontainerBeanLocator.getInstalledBean(...) on
> > every lifecycle event) that the delegate listener is deployed prior to
> > the start() of the WebServer service.
> 
> OK
> 
> > 3. There is no longer any manual step to enable mod_cluster (e.g.
> > uncommenting <depends>ModClusterListener</depends>) - the existence of
> > mod_cluster.sar is enough.
> 
> Cool ! So the mod-cluster SAR has a dependency on WebServer, and when 
> you dynamically deploy mod-cluster.sar, JBossWeb will already be 
> running, good !

Yup.

> > 4. It is still compatible with the mod_cluster configuration bundled 
> > with AS 6.0.0.M1-M3.
> 
> OK
> 
> > 5. mod_cluster is now hot-deployable, independently of jbossweb. The
> > addition of a corresponding stop() that removes the lifecycle listener
> > will allow mod_cluster to be hot-undeployable.
> 
> Great !

Yes - now mod_cluster can finally behave like a normal jboss service...

> > Thoughts?
> 
> Excellent ! I like this a lot, because it simplifies things a lot and 
> reduces the amount of configuration to be done.
> 
> So when this is done, what will the configuration steps be (on the JBoss 
> AS side) ?
> 
>    1. Add a jvmRoute to server.xml [optional, as jvmRoute is generated
>       if absent]

The default JvmRouteFactory allows system property override as well, via
-Djboss.mod_cluster.jvmRoute

>    2. mod-cluster.sar:
>          1. Set the proxy list (jboss.mod_cluster.proxyList) [optional
>             if IP multicasting works, as advertise is enabled by default]

Advertise is not enabled by default - in order to minimize jboss's
default port footprint.  Advertise can be enabled via a system property.

So, in summary, the servers just need to be started with either:
-Djboss.mod_cluster.advertise=true
or
-Djboss.mod_cluster.proxyList=....

>          2. Set the domain [optional if we use a system prop, or the
>             default domain]
>          3. Use HAModClusterService instead of ModClusterService: for
>             the mod-cluster.sar located in 'all', can we make this the
>             default ?

I alluded to this earlier when I mentioned splitting the
ModClusterListener bean into a separate conf file and creating 2
versions of it.  One using HAModClusterService for use in the all
profile, the other using ModClusterService for use in the default
profile.