Re: Odd uuid-ossp behavior on smew and shearwater

On Wed, May 28, 2014 at 11:23 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Buildfarm critters smew and shearwater are reporting regression test
> failures that suggest that the UUID library can't get a system MAC
> address:
> http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=smew&dt=2014-05-28%2023%3A38%3A28
> http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=shearwater&dt=2014-05-29%2000%3A24%3A32
>
> I've just committed regression test adjustments to prevent that from
> being a failure case, but I am confused about why it's happening.
> I wouldn't be surprised at not getting a MAC address on a machine that
> lacks any internet connection, but that surely can't describe the
> buildfarm environment. Are you curious enough to poke into it and
> see what's going on? It might be useful to strace a backend that's
> trying to execute uuid_generate_v1() and see what the kernel interaction
> looks like exactly.

Here's the result of attaching strace to an idle backend, then running
SELECT uuid_generate_v1(). AFAIR shearwater is a cheaply-hosted OpenVZ
VPS under the hood.

Josh