Re: DNS lookup for git.postgresql.org

On Wed, Jun 30, 2021 at 12:53:24PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > On Tue, Jun 29, 2021 at 11:26:54PM -0400, Tom Lane wrote:
> >> My buildfarm animals frequently complain of being unable to contact the
> >> buildfarm server. Sometimes there's an identifiable problem at my end,
> >> but usually not. A typical error looks like
> >> error getting branches of interest: 500 Can't connect to buildfarm.postgresql.org:443 (Network is unreachable) at ./run_branches.pl line 199.
>
> > OK, thanks. When no one said they saw similar behavior, I started
> > digging deeper. It seems on Debian 10, bind/named uses IPv6 by default,
> > and my ISP, Verison FIOS, doesn't support IPv6 yet; see:
> > https://www.reddit.com/r/Fios/comments/li4ri7/does_fios_support_ipv6/
>
> Oh, that's an interesting point. I have no IPv6 connectivity here either.
> I'd figured out some time ago that with recent bind versions I need to use
> named's "-4" option to prevent DNS lookup timeouts ... but now I see that
> that doesn't stop it from returning IPv6 addresses. I wonder if the
> failures occur when my animals try to use the buildfarm server's IPv6
> address. I'll try the hack mentioned in the serverfault thread.

Oh, I used the -4 option and my failures stopped. Glad this thread was
helpful for you too. I never expected IPv6 to lead to failures, just
possible delays, but I have now learned, at least with DNS, it can cause
failures too. I will also add the bind options mentioned to disable
dnssec and aaaa records.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

If only the physical world exists, free will is an illusion.