I have a CentOS 5.2 server running Apache 2.2.3 (yum installed) and drupal 6.5 on ESX 3.5. We're using Name Based Virtual Hosting on it - 2 hosts. The problem is that when I pull up a web page after not having accessed it for ~15+ minutes it takes between 10-12s to load fully. The 2nd page, 3rd page - and sometimes more than that - take between 8-12 second. After that - decent performance, though not great (0.3s to 2s). Wait ~15 minutes, maybe more, maybe less, and it goes back to slow. While it's been most apparent with httpd, I've noticed similar slowness with the initial ssh session, etc.
I know what you're thinking. DNS problem, right? Yeah, me too. But for the life of me I can't find a problem. This is at a colocation site where we have other servers - all of those are just fine. We've got an almost identical box internally - working just fine. I can do an nslookup off of each of our different internal name servers and get identical and immediate responses.
I've done tcpdumps (both on the client and the server). It shows the request gets to the server immediately. I've started httpd using strace and not seen anything glaringly wrong (though I'm not well versed in the output I have enough C under my belt to have an idea what's going on). Thinking it was code that the developer working on the project I pulled all the custom drupal modules out and it's still slow. Even created another virtual host with a stock drupal install and it's slow (identical results). I moved the mysql server from local to our central DB server. Load avg never gets above ~0.10 so I don't think the box is stressed. Watching the ESX load average it looks good too. I've tried a hell of a lot of other things and tried to include all the relevant information so apologies in advance for anything I might have left out.
Thanks, Dave
Relevant info:
uname -a: Linux internal-name.domainname.com 2.6.18-92.1.13.el5 #1 SMP Wed Sep 24 19:33:52 EDT 2008 i686 i686 i386 GNU/Linux
relevant portion of httpd.conf: NameVirtualHost *:80
<VirtualHost *:80> DocumentRoot /path/to/drupal-current ServerName publicname.domainname.com ErrorLog /path/to/logserror_log CustomLog /path/to/logs/access_log common </VirtualHost>
/etc/hosts: 127.0.0.1 localhost.localdomain localhost internal-name 12.34.56.78 publicname.domainname.com 12.34.56.79 db-server.domainname.com db-server