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From Vasile GABURICI <gabur...@ss.pub.ro>
Subject Re: Scalability/concurrent users
Date Wed, 05 Jul 2000 16:25:57 GMT
On Tue, 4 Jul 2000, John Econopouly wrote:

> 
> 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...

	Try IBM JDK 1.3.0 (alpha). AFAICT on socket business it is more
stable than Blackdown. You also get near 4-fold increase in performance.
Check: http://www.ss.pub.ro/~gaburici/nstomcat/perf/ for more on this.

	You are not saying what Tomcat version you are using, but for 3.1
beware that SimpleTcpConnector can be replaced with the faster PoolTcp*.

> 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.

	Use Apache 2 (alpha) or AOLserver 3.0 (production) with in-process
Tomcat (via JNI integration). I don't know if it will give any improvement
in capacity, but will give some in performance.

> 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?

	I don't remember what kernel RedHat 6.1 had (I skipped from 6.0 ->
6.2), but some older 2.2.x kernels had TCP/IP bugs that slowed them down.
 
> Any info at all greatly appreciated, I'm getting desperate...
> thanks
> j
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