Hello all --
Running with the following:
*3 Dell Poweredge 1950 servers (2x quad core xeons, 8 GB RAM, 146 GB 15k SAS in
Raid 1) running CentOS 5.1 x86_64
*Apache 2.0.54 with mod_jk
*Tomcat 4.1.27-LE
*jdk1.5.0_15
These 3 servers are behind a Cisco ACE load balancer. We're using SSL
offloading with the load balancer.
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.
Using mod_jk on Apache to balance our Tomcats. We have 3 tomcat instances
running.
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.
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.
We've run load tests on this several times using values that are known to work
well when we're using HTTP only (5000 concurrent users with a ramp-up of 50
users/sec.) We've monitored resources on the Cisco ACE load balancer and
things there seem just fine... no bandwidth issues, no system resource concerns.
We did have to modify the server.xml files for each tomcat instance to have a
"scheme=https proxyPort=443" on the toms to let the tomcats and app know that
we're behind an SSL offloader, not simply the http traffic that they see
traffic as.
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.
Thank you very much,
Shaun Qualheim
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