I'd like to run a web container where each webapp runs in its own process (JVM). Incoming requests get forwarded by a proxy webapp running on port 80 to individual webapps, each (webapp) running on its own port in its own JVM. This will solve three problems: Webapps using JNI (where the JNI code changes between restarts) cannot be restarted. There is no way to guarantee that the old webapp has been garbage-collected before loading the new webapp, so when the code invokes System.loadLibrary() the JVM throws: java.lang.UnsatisfiedLinkError: Native Library x already loaded in another classloader. Libraries leak memory every time a webapp is reloaded, eventually forcing a full server restart. Tomcat has made headway in addressing this problem but it will never be completely fixed. Faster restarts. The mechanism I'm proposing would allow near-instant webapp restarts. We no longer have to wait for the old webapp to finish unloading, which is the slowest part. I've posted a RFE here and here . I'd like to know what you think. Does any existing web container do this today?

Reputation: 90150

Running webapps in separate processes

I'd like to run a web container where each webapp runs in its own process (JVM). Incoming requests get forwarded by a proxy webapp running on port 80 to individual webapps, each (webapp) running on its own port in its own JVM.

This will solve three problems:

Webapps using JNI (where the JNI code changes between restarts) cannot be restarted. There is no way to guarantee that the old webapp has been garbage-collected before loading the new webapp, so when the code invokes System.loadLibrary() the JVM throws: java.lang.UnsatisfiedLinkError: Native Library x already loaded in another classloader.
Libraries leak memory every time a webapp is reloaded, eventually forcing a full server restart. Tomcat has made headway in addressing this problem but it will never be completely fixed.
Faster restarts. The mechanism I'm proposing would allow near-instant webapp restarts. We no longer have to wait for the old webapp to finish unloading, which is the slowest part.

I've posted a RFE here and here. I'd like to know what you think.

Does any existing web container do this today?

Upvotes: 3

Answers (4)

Gili

Reputation: 90150

I'm closing this question because I seem to have run into a dead end: http://tomcat.10.n6.nabble.com/One-process-per-webapp-td2084881.html

As a workaround, I'm manually launching a separate Jetty instance per webapp.

Upvotes: 1

djna

Reputation: 55937

If I understand correctly you are asking for the standard features for enterprise quality servers such IBM's WebSphere Network Deployment (disclaimer I work for IBM) where you can distribute applications across many JVMs, and those JVMs can in fact be distributed across many physical machines.

I'm not sure that your fundamental premise is correct though. It's not necessary to restart a whole JVM in order to deploy a new version of an application. Many app servers will use a class-loader strategy that allows them to discard a version of an app and load a new one.

Upvotes: 0

MJB

Reputation: 9399

No, AFAIK, none of them do, probably because Java web containers emphasize following the servlet API - which spins off a thread per http request. What you want would be a fork at the JVM level - and that simply isn't a standard Java idiom.

Upvotes: 0

Andrew White

Reputation: 53516

Can't you just deploy one app per container and then use DNS entries and reverse proxies to do the exact same thing? I believe Weblogic has something like this in the form of managed domains.

Upvotes: 0

Running webapps in separate processes

Answers (4)

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