Apache Perl/PHP/proxy DNS lookup failures

[Bob MacCallum]

Hi,

I know the cool cats don't use Apache httpd any more, but maybe someone can
help anyway..?

We (non-profit bioinformatics site maintainers) are seeing regular
intermittent DNS lookup failures from mod_perl, php and mod_proxy.  Once the
error appears it keeps occurring until you restart apache, even though on
the commandline the hosts can be looked up and contacted fine (e.g. with
ping).  We've googled the error messages many times, and we're not the first
to experience this [1,2] - for many it seems to happen when DHCP leases are
renewed on home ADSL connections, and they are happy to restart Apache.
Looking at our resolv.conf timestamps, however, DHCP renewal doesn't seem to
be the problem.

One of my colleagues hacked a version of LWP (which was failing in one web
app running in mod_perl) to use Net::DNS::Resolver instead of gethostbyname
and that seemed to work, but the problems are so widespread (database
hostname lookup in php, ProxyPass back-end lookup in Apache) that patches
like this are clearly not addressing the root cause.

The hardware is Mac running Darwin Kernel Version 9.8.0
Server version: Apache/2.2.15 (Unix)
Server built:   Oct 14 2010 16:41:03

I'm not the main admin for this machine, so I don't know much about the DNS
and DHCP setup, but can find out, of course.

Thanks for reading!  Any ideas?

cheers,
Bob.

[1] PHP:
http://www.google.co.uk/search?q=Temporary+failure+in+name+resolution
[2] Perl: http://www.perlmonks.org/index.pl?node_id=333632