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From Mike -- EMAIL IGNORED <>
Subject [users@httpd] excessive dns slows httpd
Date Tue, 04 Aug 2009 00:47:31 GMT
My web server is a CentOS box thus:

   [root ~]# uname -a
   Linux mbrc21 2.6.18-92.1.22.el5 #1 SMP Tue
      Dec 16 12:03:43 EST 2008 i686 athlon i386 GNU/Linux
   root ~]# rpm -q httpd

My development and standby is on a Fedora box thus:

   [root ~]# uname -a
   Linux mbrc32 #1 SMP Thu
      May 15 00:35:10 EDT 2008 i686 athlon i386 GNU/Linux
   [root@ ~]# rpm -q httpd

They are close neighbors on my LAN.

Now I recently revised my httpd.conf making it somewhat
more complex and adding ssl for part of it.  Running the
same configuration on both boxes, I find that the Fedora
box runs rapidly, while the CentOS box is very slow.

Examining the situation with WireShark on both boxes I
find that in responding to a simple GET, the CentOS box
does a sequence of DNS queries to resolve the details of
the location of the client IP address, whereas the
Fedora box does no such thing.  It ts these DNS queries
that are causing the slow response.

Now if I revert to the old configuration, there is no
such problem and WireShark shows that there are no DNS

Advice on how to proceed would be much appreciated.


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