Michal-
  We're in exactly the same situation (running 4.1.x), and our solution
is to isolate the most critical application(s) in their own jvm (and
tomcat instance).  Because everything is running as a single process,
it's difficult to get very fine-grained control over an app's resource
use beyond that.

  I imagine there are steps one could take to add some kind of
instrumentation on threads, etc., but I'd also have to imagine that
being an extremely heavyweight solution.  If you come up with a better
way of doing things, please post.

  Regarding your security manager comment:  You shouldn't need to write
a custom security manager- you probably just need to customize your
policy file.  You can isolate webapps by code base or signature (if
they're deployed from a war file), so you're really just limited by your
tolerance for keeping the policy file up-to-date.  The only
customization of the manager I ever needed to do was to write a kind of
"open" manager that logged missing permissions instead of throwing
exceptions:  This was to do development without having to resort to the
AllPermission "solution" that folks tend to suggest when
AccessControlExceptions start popping up.  

Benjamin J. Armintor
Systems Analyst
ITS-Systems: Mainframe Group
University of Texas - Austin
tele: (512) 232-6562
email: [EMAIL PROTECTED]
 


-----Original Message-----
From: Michal Kwiatek [mailto:[EMAIL PROTECTED] 
Sent: Tuesday, May 11, 2004 9:21 AM
To: Tomcat Users List
Subject: RE: Multihosting in tomcat


To add another point to my earlier post: I'm not concerned with
malicious code like "System.exit(1)" because a custom SecurityManager
will take care of that. What worries me is the abuse of resources
causing the server to go low on resources and crash. Perhaps installing
a separate Tomcat instance for every application is a solution?

Cheers,
Michal.

-----Original Message-----
From: Michal Kwiatek 
Sent: Tuesday, May 11, 2004 9:42 AM
To: [EMAIL PROTECTED]
Subject: Multihosting in tomcat

Hello all!

I have to set up a multihosting service based on tomcat. What I mean by
multihosting is that many people are able to deploy their web
application on the server. The problem is that the applications can be
badly written (for instance can contain unfinite loops) and thus cause
the server to go down on resources and crash.

I need a solution for:
 (1) identifing applications consuming to much resources,
 (1) killing them.

I know that it is possible to programatically stop a web application
deployed on Tomcat. But will it work if Tomcat gets low on resources?
And how will I know which application to stop in the first place?
Needless to say, it has to be done automatically.

Thanks very much,
Michal.



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