2:57 a.m.
Paul Ferraro wrote:
>
> Why ? Can't we simply grab the deployed contexts from JBossWeb ? If
> mod-cluster is started before jbossweb, we'll get the deployed contexts
> later, once jbossweb has been started. Do we get notifications about
> when beans have been started ? If so we could listen for
> jbossweb-started, and *then* grab all contexts...
Right. Scrap that old idea. Here's what I think we should do (I spent
this morning validating that this works):
Edit mod_cluster MC config such that it depends on the WebServer bean
and is no longer "On Demand". e.g.
<bean name="ModClusterListener"
class="org.jboss.modcluster.catalina.CatalinaEventHandlerAdapter">
<constructor>
<!-- To use the HA singleton version of mod_cluster, change this injection to
HAModClusterService -->
<parameter><inject
bean="ModClusterService"/></parameter>
<parameter><inject bean="JMXKernel"
property="mbeanServer"/></parameter>
</constructor>
<depends>WebServer</depends>
</bean>
Add a start() MC lifecycle method to CatalinaEventHandlerAdapter that
looks like:
public void start() throws JMException
{
try
{
// If the catalina server is already registered, init/start mod_cluster
Service[] services = (Service[]) this.mbeanServer.invoke(this.serverObjectName,
"findServices", null, null);
if (services.length > 0)
{
Server server = (Server) services[0].getServer();
if (server instanceof Lifecycle)
{
Lifecycle lifecycle = (Lifecycle) server;
for (LifecycleListener listener: lifecycle.findLifecycleListeners())
{
// Test if listener is already registered
if (listener.equals(this)) return;
}
lifecycle.addLifecycleListener(this);
if (this.init.compareAndSet(false, true))
{
this.init(server);
if (this.start.compareAndSet(false, true))
{
this.eventHandler.start(new CatalinaServer(server, this.mbeanServer));
}
}
}
}
}
catch (InstanceNotFoundException e)
{
// Ignore
}
}
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.
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 ?
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 !
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 !
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]
2. mod-cluster.sar:
1. Set the proxy list (jboss.mod_cluster.proxyList) [optional
if IP multicasting works, as advertise is enabled by default]
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 ?
WDYT ?
--
Bela Ban
Lead JGroups / Clustering Team
JBoss