[CentOS] excessive DNS slows httpd

Stephen Harris lists at spuddy.org
Tue Aug 4 01:09:21 UTC 2009

On Tue, Aug 04, 2009 at 12:33:38AM +0000, Mike -- EMAIL IGNORED wrote:
> On Mon, 03 Aug 2009 20:11:09 -0400, Brian Mathis wrote:
> > What did you revise in your httpd.conf file?  My guess is that you
> > enabled DNS lookups for the connecting clients.
> > 
> HostnameLookups Off

Precisely.  This tells apache to do DNS lookups or not.  By setting this
"off" your log files will contain only IP addresses, and any CGI program
called will only see IP addresses.  If you set this on then apache will
_for every request_ do a DNS lookup  (maybe nscd will have cached it) and
log the name.

Reverse DNS can be slow.  It's strongly recommended that web servers leave
this option off.



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