Re: FW: Job Scheduler pattern

[Mike Conway]

why not just run a crontab and forget about having orion fire anything off?

Mike

Justin Crosbie wrote:

[EMAIL PROTECTED]">

This doesn't look like it got processed, I'll send it again...

-----Original Message-----
From: Justin Crosbie 
Sent: 28 January 2002 12:50
To: 'Orion-Interest'
Subject: RE: Job Scheduler pattern


Hi again,

Thanks for the help on this. What I've done so far is this:

1. Implemented a java.util.Timer as a Singleton which is accessed from the
servlet layer.
2. Implemented a class that extends TimerTask, which does a JNDI lookup of
my EJB and invokes the 
   appropriate method.
3. Call the Singleton  from the servlet to schedule the TimerTasks as per
client requests. 
   (Plus save details to database)
4. Implemented another app to be called via the <client-module> tag which
reschedules the previously 
   scheduled TimerTasks. Thus I have my persistence.
5. The Singleton runs the ReScheduler whenever its recreated.
6. Run orion using the -userThreads parameter - this is necessary.


So, as long as my Singleton class stays up, I should be OK. The problem is,
some tasks might be scheduled for weeks or months away. How can I guarantee
that it will fire at the scheduled time even if it is this long away?

I understand that there may be several instances of the Singleton per
classloader, thats OK, as long as its a finite amount.

So. My question now is: Is this as robust as it gets? Is there anything I am
not doing, or could do to implement a better solution? All opinions welcome.

Thanks again,
Justin

-----Original Message-----
From: Paul Knepper [mailto:[EMAIL PROTECTED]]
Sent: 25 January 2002 23:07
To: Orion-Interest
Cc: '[EMAIL PROTECTED]'
Subject: RE: Job Scheduler pattern


Joseph,

Very cool.  How do you stop a client-module 
that auto-started and then
restart it?  

Say you deployed the app (which also has ejb and web modules) and later
wanted to add another task to the scheduler.  Can you start and stop the
java client module, so that it would reload the properties file, without
affecting the web module?  I might have users logged in to the website and I
wouldn't want to redeploy everthing and messup any current sessions.

Thanks,
Paul

-----Original Message-----
From: Joseph B. Ottinger [mailto:[EMAIL PROTECTED]]
Sent: Friday, January 25, 2002 4:04 AM
To: Orion-Interest
Subject: Re: Job Scheduler pattern


The www.orionsupport.com site has a sample scheduler that can easily be
converted to do something like this.

On Fri, 25 Jan 2002, Justin Crosbie wrote:

Hi,

I'm not sure if I've asked this before, or if I should be asking on a
general EJB list.

I'd like to implement a job scheduler in J2EE. This would shcedule the
execution of EJB methods at a specified time in the future. It would have

to

be persistent, and jobsd would be rescheduled upon appserver restart.

Is it as simple as using the Timer and TimerTask in java.util to implement
an app that is started with the <client-module> tag?

Does it matter as far as Orion goes whether I use a java.util.Timer as a
daemon or not?

What can I do if the app, or the Timer object dies at any stage?

I've had problems where after some time something goes wrong I get a

strange

Remote Exception, and the only solution is to restart the VM. What might
cause this?

Any opinions on this? How do I make this solution robust is what I am
asking.

Thanks for any help,
Justin

-----------------------------------------------------------
Joseph B. Ottinger                       [EMAIL PROTECTED]
http://adjacency.org/                         IT Consultant