CUPS and DNS

[angelb]

Hello all.

Recently we've experienced a problem with our CUPS printing because
of our Windows DNS servers started having issues.

On a normal day, when I do an lpstat on a printer queue, it returns
within 5-7 seconds. When the DNS servers are having issues; hung, CPU
load, etc, the same command, lpstat returns in about 35-40 seconds.

I ran some traces to see how CUPS calls for name resolution and found
that it open/read /etc/netsvc.conf and /etc/resolv.conf, among other
things. In the same trace, I also see that cups do a TCP_kconnect on
the first name server in the resolv.conf. It opens additional files
before it actualy returns the results(4-7seconds later)

What I don't see(or don’t understand) is how CUPS reference a secondary
DNS server listed in the resolv.conf file. I intentionally entered a
non-responding IP address in resolv.conf as the first entry, an lpstat
command will return after a period of time(30-40seconds later) but
there is no trace(or at least I don't see it) of how CUPS use the
secondary server. How is it done?

Can someone please explain this so that I can have a better understanding and take CUPS out of the picture from our DNS issue.

Thanks,
Angel