[CentOS] excessive DNS slows httpd

Tue Aug 4 00:11:09 UTC 2009
Brian Mathis <brian.mathis at gmail.com>

What did you revise in your httpd.conf file?  My guess is that you
enabled DNS lookups for the connecting clients.


On Mon, Aug 3, 2009 at 7:48 PM, Mike -- EMAIL
IGNORED<m_d_berger_1900 at yahoo.com> wrote:
> 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
>   httpd-2.2.3-22.el5.centos.2
>
> My development and standby is on a Fedora box thus:
>
>   [root ~]# uname -a
>   Linux mbrc32 2.6.23.17-88.fc7 #1 SMP Thu
>      May 15 00:35:10 EDT 2008 i686 athlon i386 GNU/Linux
>   [root@ ~]# rpm -q httpd
>   httpd-2.2.8-1.fc7
>
> 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
> queries.
>
> Advice on how to proceed would be much appreciated.
>
> Thanks,
> Mike.
>
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