[CentOS] Possibly OT: intermittently long response times when connecting to host

On Tue, 2008-10-28 at 16:30 -0500, David Miller wrote:
> 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
----
sounds sleepy - perhaps the mysql connections drop after inactivity and
then it takes that long to connect

You might just want to set up a cron script that does a curl or wget of
a standard page every 2 minutes or so just to keep things active.

Craig