Hi,

>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?

OK, now we're getting more realistic ;)

A separate tomcat instance per application means much less worrying
about them killing each other.  Any one app can only damage itself.
This is great from a security and stability perspective, but can be a
nightmare to administer (although if you have a nice JMX console, you're
in much better shape as you can configure it with all your tomcat
instances and control them from one place).

But since you're already handling some things with a custom security
manager, and are only concerned with the resources, here's one
additional possible approach.

Create a listener (probably the tomcat-specific Lifecycle Listener), but
can be a more portable ServletContextListener tied to the admin or
manager webapps for example, or to a webapp that will always be present
on your server.  Have this listener spawn a (daemon) thread that
monitors memory usage (via Runtime.freeMemory etc.), and when it drops
below a certain percentage takes action.  The action can be to notify
the administrator, or do tomcat specific-things (like accessing the
manager webapp programmatically to stop/restart/undeploy applications).
You will not know which application is causing the problem.  You also
won't be able to monitor CPU usage, which is the problem in cases like
infinite loops.  But it's something.

Yoav Shapira




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