mod_webapp and multithreading for concurrent requests

[Eliot James Ormond Stock]

Hi all,

I'm running Apache 1.3.27, Tomcat 4.1.12 (both as services on Win32) with mod_webapp, and I need someone to explain to me how mod_webapp passes requests to Tomcat. The docs are a bit thin.

I have a couple of test servlets: waiter and notifier. When I hit the waiter it blocks waiting for the notifier to notify it. When I hit the notifier it notifies the waiter and writes some output to the browser. The waiter then writes some output too so I can see that both have finished.

I actually have Tomcat set up with both the WARP connector listening to requests that come via Apache, and the Coyote connector listening to requests diurectly on port 8080.

When I hit the servlets on port 8080 everything works as expected. But when I hit them on port 80, via mod_webapp, there's a problem: the notifer never gets to execute. It seems mod_webapp is behaving as if it's a single thread (I have read stuff that suggests it is not, and I would hope it's not for obvious performance reasons). What I'm seeing is that the request for the writer is handled just fine up to the point where it blocks, but when I hit the notifier the request is never processed because the thread is still handling the waiter request.

Can anyone shed any light on this?

Thanks in advance,

Eliot Stock
Picopoint BV






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