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From Riaan Oberholzer <riaanoberhol...@yahoo.com>
Subject Re: [Q] Is it safe to create threads in Tomcat web-apps? (JCrontab)
Date Mon, 28 Jul 2003 11:25:03 GMT
This looks promising, but what do they do differently
than just starting a deamon thread and doing some
background work?

Why bother with this if you can start your own custom
thread, or do they do something else?



--- Kwok Peng Tuck <pengtuck@makmal.net> wrote:
> Hello Riaan, you might want to check out jcrontab.
> 
> http://jcrontab.sourceforge.net
> 
> Riaan Oberholzer wrote:
> 
> >Well, that was part of my question.... if I
> >cannot/don't implement daemon threads to do e.g.
> >automatic daily tasks, what else? E.g, at the end
> of
> >the day send an e-mail to a (real life) manager
> with a
> >summary of the day's transactions.... something
> like
> >that.
> >
> >Does Tomcat provide some sort of ActionEvent which
> you
> >can configure to be fired every x milliseconds?
> >
> >
> >
> >--- Tim Funk <funkman@joedog.org> wrote:
> >  
> >
> >>You can create threads all day in tomcat, but here
> >>are the importnatn things 
> >>to consider:
> >>- WHY! Are threads really the correct solution?
> >>- If you create threads - what are their scope?
> >>Daemon, non-daemon?
> >>- If you create non-daemon threads - be prepared
> for
> >>the consequences such as 
> >>the JVM not going away on tomcat shutdown unless
> you
> >>have taken the needed 
> >>precautions.
> >>- If you create dameon only threads, be prepared
> for
> >>when tomcat shuts down 
> >>and your daemon still has work to do because the
> JVM
> >>could exit before your 
> >>thread is ready to complete its unit of work
> >>- WHY! Are threads really the correct solution?
> >>- And last but not least: WHY! Are threads really
> >>the correct solution?
> >>
> >>-Tim
> >>
> >>Riaan Oberholzer wrote:
> >>    
> >>
> >>>I've mainly worked in BEA WebLogic before and
> from
> >>>colleagues and other sources I have heard it is
> >>>      
> >>>
> >>not
> >>    
> >>
> >>>recommended (and sometimes not allowed, some even
> >>>said) to create threads in your application.
> >>>      
> >>>
> >>Indeed,
> >>    
> >>
> >>>when the application went live in a multi-server
> >>>clustered environment, we got very inconsistent
> >>>results because of the threads, so we had to
> >>>      
> >>>
> >>remove
> >>    
> >>
> >>>them.
> >>>
> >>>Question is, how safe is it to create threads in
> a
> >>>Tomcat web-app? I would assume "worker" threads
> >>>      
> >>>
> >>are
> >>    
> >>
> >>>ok, i.e. threads you create to do a specific task
> >>>      
> >>>
> >>and
> >>    
> >>
> >>>then it terminates. When you are guaranteed the
> >>>      
> >>>
> >>thread
> >>    
> >>
> >>>will terminate either because of an error or
> >>>      
> >>>
> >>because
> >>    
> >>
> >>>the assigned task has been completed.
> >>>
> >>>But what about "monitor" threads, i.e. threads
> >>>      
> >>>
> >>that
> >>    
> >>
> >>>does a Thread.sleep(x) for an hour, check some
> >>>condition and goes back to sleep... some
> mechanism
> >>>      
> >>>
> >>you
> >>    
> >>
> >>>implement to e.g. do a task on a
> >>>      
> >>>
> >>hourly/daily/weekly
> >>    
> >>
> >>>base. You'd create the thread (and keep a handle
> >>>      
> >>>
> >>to
> >>    
> >>
> >>>it) in either an InitServlet.init() and then
> >>>Thread.interrupt() in the InitServlet.destroy(),
> >>>      
> >>>
> >>or
> >>    
> >>
> >>>you can do it in an ApplicationListener
> (something
> >>>like that) class which I think you can define in
> >>>      
> >>>
> >>the
> >>    
> >>
> >>>web.xml.
> >>>
> >>>How else can you implement that (monitoring) in
> >>>Tomcat?
> >>>      
> >>>
> >>
> >>    
> >>
>
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> >>    
> >>
> >
> >
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> >  
> >
> 
> 
>
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