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From Remy Maucherat <r...@jboss.org>
Subject Re: When is Tomcat 5 Release version scheduled to come out?
Date Sat, 22 Nov 2003 14:29:58 GMT
Antonio Fiol Bonnín wrote:
> Hello,
> 
> I'll begin from the end...
> 
> I did not present evidence, that is true, but I explained the symptoms. 
> I tested three configurations:
> 
> 1 Apache + 1 Tomcat;    1 Apache + 2 Tomcat;    1 Apache + 3 Tomcat
> 
> All three gave me very similar performance results. Measurement tool was 
> "JMeter". Difficult pages were generated faster using three tomcats than 
> using one tomcat, and trivial pages were faster with one tomcat.
> 
> Probably all this is due to the overhead of replicating the sessions, 
> but I am not sure.
> 
> We also used Apache AB to test it. We did it against one nearly static 
> JSP page. With low concurrency levels (less than 5), 2 tomcats give more 
> throughput than one. With higher concurency levels (5 or more), 2 
> tomcats give worse throughput.
> 
> Probably, again, I think, because of the overhead of creating hundreds 
> of sessions and replicating them. But, again, I am not sure.

You don't pretend to win the coveted Whiner Of The Month award with 
this, I hope. There's a lot of competition, you know.

A little more seriously:
- JMeter is IMO a bad load testing tool, but it's good at testing latencies.
- With your AB test, you are likely creating a session each time, which 
is basically the worst case for session clustering.
- You have to use session stickiness (the Servlet specification requires 
that operations related to a sigle session be bound to a single VM).
- JBoss session clustering is very likely a little more optimized 
(although it is not currently ported to Tomcat 5; coming soon).

You'll get better performance out of this form of clustering only if 
your webapp does a significant amount of computations. XML stuff is the 
prime example. If you are mostly DB based, you'll be moving the 
contention problems to the DB layer.

Given the throughtput a single Tomcat 5 with its HTTP connector gives on 
a decent server, I am surprised you are having problems unless you app 
is really processing intensive or your expected traffic is really high.

-- 
xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Rémy Maucherat
Senior Developer & Consultant
JBoss Group (Europe) SàRL
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