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From "Clark, Tom" <tom.cl...@compaq.com>
Subject RE: Running multiple servlet instances
Date Wed, 02 Feb 2000 19:28:26 GMT
The mechanism would need to cache the instances and select among them when
each request is   received.  But they don't need to be run one at a time,
they can be run concurrently.  Each instance is single threaded, but not the
class as a whole.  
  Does Tomcat currently queue up requests when a servlet is busy?  Would
this also work for a pool of servlets?

  Tom

-----Original Message-----
From: Craig R. McClanahan [mailto:cmcclanahan@mytownnet.com]
Sent: Wednesday, February 02, 2000 11:01 AM
To: tomcat-dev@jakarta.apache.org
Subject: Re: Running multiple servlet instances


The current Tomcat code just calls the servlet's service() method inside a
"synchronized" block if the servlet implements SingleThreadModel, and calls
it
directly if not.  In order to support more than one instance, you'd need to
add
just that -- a mechanism that manages a cache of instances, makes sure you
call
just one at a time, allows configuration of the cache size, and (most
important)
deals correctly with the case where all your current instances are in use
and a
new request comes in.

Craig


Brill Pappin wrote:

> I'd agree that SingleThreadedModel is *not* a nice way to do anything...
but
> I have found it useful in one or two odd situations... What would be
> required to implement it?
>
> - Brill Pappin
>   www.jmonkey.com
>
> ----- Original Message -----
> From: Booth, Peter <peter.booth@csfb.com>
> To: <tomcat-dev@jakarta.apache.org>
> Sent: Wednesday, February 02, 2000 5:07 PM
> Subject: RE: Running multiple servlet instances
>
> > Tom,
> >
> > SingleThreadedModel is a kluge. I used the interface in the
> > previous servlet project I deployed , because server-side
> > performance didn't seme to be an issue and it turned out fine.
> > The servlet pooling in WebSphere 1.1 worked acceptably.
> >
> > In my latest project I have written my servlets to be
> > multithreaded. I still use different servlet instances
> > by registering multiple servlet names (with different
> > init parameters) that use the same servlet code and this
> > works as expected. I haven't tried this with tomcat.
> >
> > Peter Booth
> >
> >
> > -----Original Message-----
> > From: Clark, Tom [mailto:tom.clark@compaq.com]
> > Sent: Tuesday, February 01, 2000 6:37 PM
> > To: 'tomcat-dev@jakarta.apache.org'
> > Subject: Running multiple servlet instances
> >
> >
> > Hi,
> >   I'm trying to run some SingleThreadedModel servets with tomcat and I
> can't
> > seem to get more than one instance of each to start up.  I've put
multiple
> > <servlet> ...<\servlet> clauses in my web.xml and they all go thru the
> > init() method, but when I try to run them with our loadrunner tools,
only
> > one of each class runs the service() method.  The duplicate instances
> don't
> > get activated.
> >   In reading the SingleThreadedModel documents, it talks about having a
> pool
> > of servlet instances and running multiple instances for multiple
requests,
> > but I don't see this happening in tomcat.
> >   Anyone know if this is supposed to work and if so, how to make it
> happen?
> > Any help is appreciated.
> >
> >      thanks,
> >         Tom Clark
> >
> > Tom.Clark@Compaq.com
> >
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