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From "John Econopouly" <john...@hotmail.com>
Subject Scalability/concurrent users
Date Tue, 04 Jul 2000 13:38:12 GMT

I'm trying to get tomcat to work with alot of concurrent user connections.
So far, I can't seem to get it to work past about 250, and it seems very
slow - do any of you feel it can handle more?  I was hoping for 1000...

Details:
I'm running Redhat Linux 6.1, on a 500 MHz 686 w/ 1 gig of memory.
I'm using the Blackdown 1.2.2 JVM, and have tried up to -Xms512m -Xmx768m,
-green vs -native, jit/no jit.  I also tried the Sun JVM 1.2.2.  None of
this seems to have much affect - adding all that memory just sped it up
a bit, but once I went past 250 concurrent users, some users got dropped,
I got connection exceptions, etc.  I've been wondering if there is a hard
limit of 256 somewhere in the code...

Why I'm doing this:
I need to create a "push" system, where I send changes in price information
to a large number of clients (1,000+), all behind firewalls, in real-time
(a few seconds...).  So I was planning to have applets on the client side
that make HTTP get requests which are handled by a servlet that blocks in a
wait() state until there is information to return.  So all these connections
remain open, with (at least) one blocked thread each, until they all return.

Besides dropping alot of users beyond 250, the speed seems extremely slow.
It appears like it adds a second to the response time for every 30 extra
concurrent users.  I also tried using an apache front end, but that just
made performance even way slower, without improving capacity.
I've increased my maximum file descriptors into the thousands...
I've also seen some talk about maximum tasks - but don't know what they
are... can that be what's limiting me?

Any info at all greatly appreciated, I'm getting desperate...
thanks
j
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