Thanks for your reply Chris. My responses are inline.
> > Shaun,
> >
> > On 7/8/2009 1:35 PM, Shaun Qualheim wrote:
> >> *Tomcat 4.1.27-LE
> >
> > You might consider upgrading at some point. 4.1 is getting ready to be
> > retired, and the 3 (yes 3!) versions since then all have significant
> > performance improvements that may help your situation.
Yeah, it's on the burner and scheduled for December. Unfortunately, it out of
my control until recently :).
> >
> >> Apache is listening on ports 80 and 81 using http. Port 80
> >> immediately rewrites everything to an https:// url. That https:// url
> >> goes to the load balancer on 443 and is passed to the appliance on port 81.
> >
> > Wait... what?
> >
> > client -- http:80 --> httpd -- https:443 --> lb -- http:81 --> Tomcat?
Basically. We could clear things up a little bit though, just going to
https:// right away:
client -- https:443 --> lb --> http:81 --> apache --> mod_jk --> 1 of 3 tomcats.
> >
> > You said you have 3 TC instances. Is that 1 instance on each of 3
> > separate physical servers, so port 81 is used on them all?
Apache listens on port 81 (http) on each physical server -- mod_jk load
balances each of 3 toms on each physical server. Each of 3 physical servers
has 3 tomcats running.
> > Why bother
> > with SSL after the request is within your network?
We don't -- at least as soon as it hits the load balancer.
> > Also, why have httpd
> > forward all traffic to a load-balancer instead of just doing the
> > load-balancing itself?
How do you mean? (Sorry, I can think of a few things that you might mean here,
but I don't want to assume.)
> >
> > Maybe I have misunderstood your setup, but it seems overly complicated.
> >
Could be. I do appreciate your suggestions on how to make it simpler.
> >> When we use the our application with all http (port 80 doesn't
> >> rewrite,) the system works fine when we run a load test. We can push
> >> 2100 concurrent users out of each server.
> >
> > Okay.
> >
> >> However... using the same setup beyond the load balancer, we are
> >> only about to get to about 2500 concurrent users across the three
> >> servers (about 800 per server) before we start seeing very long
> >> delays (1-2 minutes where we should be seeing a few seconds) on
> >> miscellaneous functions throughout the application.
> >
> > Does the load-balancer have any kind of traffic shaping or
> > bandwidth/connection limiting configured?
No.
> >
> > What do your elements look like in Tomcat's server.xml?
> >
Here's an example of the connector. I can provide more if it would help?
<Connector className="org.apache.coyote.tomcat4.CoyoteConnector"
port="7019" minProcessors="256" maxProcessors="1024"
enableLookups="false" redirectPort="7443"
acceptCount="10" debug="0" connectionTimeout="120000"
useURIValidationHack="false" scheme="https" proxyPort="443"
protocolHandlerClassName="org.apache.jk.server.JkCoyoteHandler"/>
> >> We're pretty perplexed on why the sudden slowdown happens at about
> >> 800 users per server. It works fine when we're http only. We don't see
> >> anything that stands out in the apache or catalina logs that would seem
> >> to be concerning (broken pipes, abnormal timeouts, etc.) I would greatly
> >> appreciate any help anyone can offer us.
> >
> > So, does it look like you are hitting a wall (like there aren't enough
> > connections allowed) or does the application/server start to experience
> > an actual slowdown (like high CPU load, lots of paging, etc.)?
> >
If I had to guess, I'd say the former. When we're monitoring system resources
using nmon during the load tests, everything else seems fine.
Thank you much for your help :)
Shaun
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