[CentOS] DNS lookup delay with centos & postfix

Wed Jul 25 21:47:55 UTC 2012
Steve Lindemann <steve at marmot.org>

On 7/25/2012 3:21 PM, Tom Brown wrote:
> Does dig use libresolv or read directly from resolv.conf? Also do you have a timeout configured in resolv.conf or are you relying on the os default?

dig uses resolv.conf and no timeouts are configured there.  I don't know 
there the OS would have a default configured or what it is.  Another 
reply indicated there would be a 5 second delay.  That seems a bit high 
to me.

I used dig from the email svr command line with the primary DNS svr up 
and (naturally) it pulled from there as normal.  Then I downed the 
primary DNS svr, saw the nagios check fail and tried again.  The same 
dig lookup was actually faster and pulled from the secondary DNS svr 
just fine.  And, again, the nagios alert cleared as soon as the primary 
DNS svr was back online.

For both tests I used:  dig mx google.com