Developer,
Hello. I use Tomcat 4.1.12 standalone. I was just thinking about what you were
saying, especially "[...] I would think the memory stamp would correspondingly shrink
when all these sessions are closed and it doesn't".
I noticed this section in the default "web.xml":
<!-- ==================== Default Session Configuration ================= -->
<!-- You can set the default session timeout (in minutes) for all newly -->
<!-- created sessions by modifying the value below. -->
<session-config>
<session-timeout>30</session-timeout>
</session-config>
So, by default on my machine sessions will stay around for 30 minutes, unless either
"session.setMaxInactiveInterval()" or "session.invalidate()" was called. I haven't
changed this file since I installed Tomcat, and so I'm assuming you have the same file.
Are you calling either of those methods - invalidate or setMaxInactiveInterval? Or
when you say "these sessions are closed", do you mean they time out after 30 minutes?
Secondly, what are you doing to generate all this (server-crashing!) load? Obviously
you're not going to call "session.invalidate()" on the same page that you created the
session. That would be pointless... so here comes an interesting possibility:
suppose a significant portion of your load didn't support cookies? Or, if you were
using URL rewriting for the sessions, suppose you forgot to use
"response.encodeURL()"? In both cases the result is the same:
Sessions are being created for a client, but the client won't remember his special
"session id". This means a new session is created for this client with every request
he makes!
So, I have three questions I need to know:
1.) What kind of load is Tomcat experiencing on your machine, and where is this load
coming from?
2.) Does your load support cookies? Is the "session id" being remembered by the
client?
3.) How are you closing your sessions?
Suppose each of your sessions weighed in at 512 bytes. If your load, at, let's
pretend 10/hits second, didn't support cookies, you're going to need ~15mb to hold on
to 30 minutes of sessions before they start expiring. This is because each hit is
going to create a new session.
Tomcat User please correct any mistakes I may have made here!
Julius Davies, Programmer, CUCBC
Email: [EMAIL PROTECTED], Ph: 604.730.6385
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
> Sent: Monday, December 02, 2002 1:24 PM
> To: Tomcat Users List
> Subject: Re: Memory/Performance
>
>
> Thanks for your comments. Well all my jspcode is definitely
> session happy
> and I am creating several
> objects per session. The objects I am creating consist of mostly
> string, int and floats, probably up to like 20 of each.
> Although i create
> a large application pool of jdbc
> connections I am fairly positive that this is not the problem
> because I
> use this pooling model in several applications that don't
> seem to have a
> problem. I realize that every time a session is created all
> these objects
> must be allocated, and that should cause the memory blob to
> keep growing
> as the session count increase but I would think the memory stamp would
> correspondingly shrink when all these sessions are closed and it
> doesn't. I am basing this on tomcats crashing or slow behavior
> in conjunction with monitoring the processes and memory
> usage. What other
> information can I share that would help? Like I said I don't
> know if this
> is tomcat or me or a bit a both so I am jsut throwing out
> what seems to be
> going on and looking for insight?
>
>
>
>
> On Mon, 2 Dec 2002, Michael Nicholson wrote:
>
> > I suppose it depends on what you're doing, which,
> unfortunately, I don't
> > know.
> >
> > If you're overly filling your session w/ objects, or if you
> have a session
> > scoped bean that is spiraling out of control or something,
> that might lead
> > to the problem, or if you create/leave open jdbc
> connections or stuff like
> > that. I'm running tomcat 4.03 on a much less beefy system,
> and I don't ever
> > notice any memory issues, now that I make sure I close and null my
> > connections and such.
> >
> > More info on what's happening might help, though..
> >
> >
> > ----- Original Message -----
> > From: <[EMAIL PROTECTED]>
> > To: "Tomcat Users List" <[EMAIL PROTECTED]>
> > Sent: Monday, December 02, 2002 3:51 PM
> > Subject: Memory/Performance
> >
> >
> > > I find that tomcat's memory stamp grows continually until
> eventually there
> > > are out of memory errors or it just bogs down. I am
> running on jdk1.4_1,
> > > tomcat 4.1.12, apache 1.27, mod_jk on the linux 2.2
> kernel. The box I am
> > > operating on has 1gig of memory and has dual gigahertz
> processors. I
> > > believe that tomcat has some serious memory leaks and/or
> I am not writing
> > > my jsppages properly. So i would like to ask two questions:
> > >
> > >
> > > 1)Assuming tomcat has memory issues what can I do to control them?
> > >
> > >
> > >
> > >
> > > 2)What techniques would you suggest to write jsppages
> that help keep
> > > memory consumption down? Are there ways to write
> jsppages that makes them
> > > more "garbage collection friendly"?
> > >
> > > please comment....
> > >
> > >
> > > --
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> > >
> >
> >
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