tomcat isolate webapps

multiple webapp running on same tomcat using same jvm. sometime, one webapp that have memory leak will cause entire jvm to crash and affect other webapps. any recommendation how to isolated that without need to use multiple jvm and t开发者_如何学运维omcat

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Within the same JVM everything shares the the same memory. There is no system to allocate separate pools or quota.

If one of your applications behaves really badly in this regard, the only thing you can do is run it isolated in a separate JVM (separate Tomcat).

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Are the applications running as separate processes? Or the same one?

First off you should look at profiling to find the memory leak https://stackoverflow.com/questions/1716597/java-memory-leak-detection-tools.

However, as a quick solution from inside you could use Runtime.getRuntime().totalMemory() to see how much memory is in use, and if it grows above a certain limit, and you know which app is causing the problem, you could restart that app.

You could also try running System.gc() which is a terrible way to do it, and really shouldn't be used as it can be ignored by the JVM.

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To the best of my knowledge, the short answer is: No, it can't be done. Tomcat uses a single memory space for all running apps.

My knee-jerk response is that you should fix the memory leak rather than trying to isolate the misbehaving app. Cure is better than quarantine. As I don't know the details of your problem, maybe this isn't practical for some reason.

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You can't isolate apps in the same JVM (though you can do things like instrument a particular apps ClassLoader for diagnostics)

If your concern is administration/configuration though (and not total memory consumption) you can run multiple instances of Tomcat off the same install by using catalina.home and catalina.base

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JSR 121 was designed to solve this, but it hasn't been implemented yet.

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There is no standard system in Java to truly isolate memory used by web applications.

However, you could write some byte-code weaving logic to track how much memory a particular app has allocated. If it goes over a particular threshold, you could throw an exception and stop the app from allocating anymore memory. What do you want to do if you could track all the memory consumed by a web app? What are you trying to implement?

Note that this would only really work effectively for figuring out how much memory a webapp has allocated, not how much it is currently consuming in the system. In order to get that metric, you'd have to byte-code weave finalize() for all objects. Since finalize() gets run in a best-effort fashion by the JVM, this may not get you the most accurate value should the system be under load. The JVM would deprioritize these finalize threads and your value will never get updated even though objects have been cleaned up.

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To bring this up to date, it is now possible to run multiple applications on a single JVM. Applications run in isolated java virtual containers which protect your applications from 'noisy neighbours' as well as allowing you to share resources across your applications. This gives you isolation, elasticity and increased application density for Apache Tomcat. Download it from www.elasticat.com NB I do work for Waratek who developed this new JVM