I wouldn't describe this as Basic JMX :-)
If you start a timer on each node then the notification will happen on each machine.
There is no spec defined mechanism for dealing with this sort of problem. This will have to considered when we write the EJB2.1 timer service.
There are a number of ways of dealing with this, it depends on what you are trying to achieve.
1) Hold some distributed state saying when the last run was (this could be in the database), only do the entity bean call if the run was not within a certain period.
2) Elect a master node. Javagroups has the notion of a controller which is the oldest node in the cluster. Only do the entity bean call if you are the master.
3) Write a distributed timer service. The timer service has the notion of a "notification sequence". The distributed timer would only fire events if the sequence had not been triggered on some other node. And perform some sort of wait while one node is notifying in case it fails during the notification. Slow nodes and new nodes would have to keep in step with the latest sequence.
Regards, Adrian
From: "Brian McSweeney" <[EMAIL PROTECTED]> Reply-To: [EMAIL PROTECTED] To: <[EMAIL PROTECTED]> Subject: Re: [JBoss-user] Basic JMX question Date: Mon, 24 Feb 2003 10:33:59 -0000
Hi Adrian, thanks very much for your answers. I have a few little questions about the clustering answers that perhaps you can give me advice on.
> You will find many adaptors/connectors already implemented, > jboss has rmi/ejb/html and jboss.net versions. > The html and ejb versions should work with clustering if > suitably configured, but the MBean state is not > replicated across the cluster. > > JBoss4/jbossmx standalone already has what will become our > implementation of jsr160 - JBoss Remoting
I have an MBean which I want to receive timed notifications from the Timer service. When it is notified I want the MBean to change the state of an Entity bean. This is fine on a single jboss version, but what I'd like some advice on, is how clustering will affect this. If I cluster and have one MBean for every box that does the same thing, will the Entity beans state get changed several times? Will each MBean get notified by a separate timer service each of which may become out of sync?
what would your advice be?
thanks very much again, Brian
----- Original Message ----- From: "Adrian Brock" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, February 19, 2003 6:16 PM Subject: Re: [JBoss-user] Basic JMX question
> Hi Brian,
>
> Answers in line.
>
> >From: "Brian McSweeney" <[EMAIL PROTECTED]>
> >Reply-To: [EMAIL PROTECTED]
> >To: <[EMAIL PROTECTED]>
> >Subject: [JBoss-user] Basic JMX question
> >Date: Wed, 19 Feb 2003 16:03:24 -0000
> >
> >Hi all,
> >yet again in my quest to write container independent code, I'm stuck. :-)
> >
> >I want to use the Timer service in a container independent manner. The
> >sheduler services for example isn't container independent :-(.
> >
> >So, the first problem I have here is, I need to get a reference to the
> >MBeanServer
> >object. Now I know that JMX isn't standard in J2EE until version 1.4 but
> >does the code
> >
> >MBeanServerFactory.findMBeanServer(null);
>
> Yes, the other method is for your MBean to
> implement javax.management.MBeanRegistration
> This is how jboss's ServiceMBeanSupport provides
> the getServer() method.
>
> >
> >work in JBoss? If so, at least I'll be writing forward compatable code
:-)
> >Also,
> >I think Weblogic uses JMX already too so this might work too.
> >
> >also, is an MBeanServer per jvm? What happens when you cluster?
>
> The MBeanServer is a purely local concept (same jvm)
> The standard for remote access to an MBeanServer (jsr160)
> has has not been released for public review yet.
>
> You will find many adaptors/connectors already implemented,
> jboss has rmi/ejb/html and jboss.net versions.
> The html and ejb versions should work with clustering if
> suitably configured, but the MBean state is not
> replicated across the cluster.
>
> JBoss4/jbossmx standalone already has what will become our
> implementation of jsr160 - JBoss Remoting
>
> >
> >thanks,
> >Brian
>
>
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