wglasshusain at gmail
Aug 31, 2007, 2:23 AM
Views: 193
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performance problem in one virtual host
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Hi,
I've had a bizarre performance problem earlier this week and I can't figure
it out. It'd be great if anyone had suggestions.
Twice recently, I've had extremely slow performance serving static files
from a single virtual host on my Apache server. Files that were sent to
Tomcat with mod_jk returned quickly, and files on other virtual hosts on the
same machine returned quickly. But every 1 in 3 static files served by
httpd in the affected virtual host took several seconds to return,
irrespective of size. (e.g. a 12 kb image could take 6 seconds to return).
A couple of notes:
* Server load was low and swap space was barely being used
* The problem appeared out of nowhere (no config changes) happened for an
hour and went away. A week later it appeared for about 4 hours, then again
fixed without warning.
* When I copied all the web files to a different virtual host on the same
box,it was lightening fast.
* I suspected DNS/reverse DNS issues. But I ran a tcpdump on port 53 and
saw no signs of DNS queries
* I had large log files. I renamed them and stopped/started httpd. Still
slow.
* I ran a web analyzer on the Apache logs. Traffic was exactly average.
* When I accessed the server from a machine on the same subnet, access was
fast! So network distance (or maybe IP address) plays a role.
One of my colleagues suspected the problem was strange registry settings at
our top level domain. We were using nameservers from two different vendors
for reliability. (and when we tested them, there was a serial number
mismatch between them). But I hardcoded the DNS on my client in /etc/hosts
(or the equivalent) and still saw the problem.
Any pointers on what I should look for to diagnose this problem / prevent it
in the future? I'm really at a loss as to what to do.
We're running Apache 2.0.52 on RHEL 4, on a dual core, dual Woodcrest
processor machine with 4GB Ram (also runs MySQL and Tomcat). The machine is
in a data farm in Texas somewhere.
Thanks,
WILL
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performance problem in one virtual host
