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From Dakota Jack <dakota.j...@gmail.com>
Subject Re: How to run servlet for every 30 minutes in Tomcat 4.1.30
Date Tue, 28 Dec 2004 17:30:51 GMT
The minimum thread priority is 1, maximum is 10 and medium or normal is 5.  See:

http://java.sun.com/j2se/1.4.2/docs/api/constant-values.html#java.lang.Thread.NORM_PRIORITY

You can set a "good neighbor poilicy with MIN_PRIORITY.  Hunter on
Servlets covers this with a daemon servlet.

Jack


On Tue, 28 Dec 2004 11:49:13 -0500, Frank W. Zammetti
<fzlists@omnytex.com> wrote:
> 
> Dennis Payne wrote:
> > Frank,
> > I'm using threads and didn't know I was vulnerable.
> 
> I'm not sure "vulnerable" is really the right word, but I'll go with it :)
> 
> > Here's how I've
> > done it.  I created a class that implements runnable and call its
> > initialize method from a servlet init method at application startup.
> >  The initialize method creates a thread and sets a low priority for it.
> 
> Roughly what I do too, except that my class extends Thread and I kick it
> off from a Struts plug-in.  Same effect though.
> 
> >  The run method sleeps the thread and wakes it every two minutes.
> > A processing class contains the methods that queries the database
> > (postgres).
> 
> Same here.  I think I wake my threads every minute though.
> 
> > 1. Is this what you call a daemon thread?
> 
> Nope.  If you take a peak at the javadocs for the Thread class, you'll
> see a method setDaemon(boolean).  This marks a thread as a daemon
> thread.  The difference, if I remember correctly, is that the JVM won't
> shut down until all remaining threads are daemon threads.  Threfore, if
> you spawn a "normal" thread, you can hold up the JVM from shutting down
> properly.
> 
> This is in fact the situation I had... My Tomcat instance could never be
> properly shut down because the threads I had spawned where not daemon
> threads.  Marking them as such solved that problem.
> 
> To the best of my knowledge, being a daemon thread doesn't implicitly
> say anything about a threads priority.  I think you could have a daemon
> thread set at high priority if you wanted.  I suspect most daemon
> threads are bumped to a lower priority though, as I do.
> 
> > 2. Is this better done using cron?  if so how do I ensure that it runs
> >
> > with a lower priority than my application code?
> > Phil
> 
> This is a matter of opinion, and there are some reasonable arguments for
> both points of view.
> 
> My personal opinion is that if you have some periodic process that is
> going to need portions of your system, whether it's resources available
> in the container or shared code, as you do, then a low-priority daemon
> thread spawned at application startup is a good approach, assuming you
> write it carefully and solidly.
> 
> For instance, in my case, my daemon threads do some record aging in the
> database, so to me it makes sense to share the same connection pool as
> the application itself.  I also use a number of classes and functions
> that are part of the webapp itself, and I don't like the idea of
> duplicating the code for a cron job to use (sure, could just be a matter
> of setting up a classpath to those classes, but it's an extra
> dependency, and that doesn't thrill me).
> 
> But, if these tasks were volatile in any way, or they had to run
> independently of the app itself no matter what, the cron job approach
> would probably be preferable.
> 
> As for ensuring it runs at a lower priority than your application code,
> when running via cron, that's an answer I can't give you.  I'm frankly a
> Unix newbie, more or less, so someone else out there would be better
> suited to answer that.  I think you'd have to have it run at a lower
> priority than your app server, and I'm sure there's switches to set
> priority of jobs, but I don't know them.
> 
> --
> Frank W. Zammetti
> Founder and Chief Software Architect
> Omnytex Technologies
> http://www.omnytex.com
> 
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> 


-- 
------------------------------

"You can lead a horse to water but you cannot make it float on its back."

~Dakota Jack~

"You can't wake a person who is pretending to be asleep."

~Native Proverb~

"Each man is good in His sight. It is not necessary for eagles to be crows."

~Hunkesni (Sitting Bull), Hunkpapa Sioux~

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