[Python-Dev] Buildbot timing out - test suite failure - test_socket issue with UDP6?

[Chris Angelico]

I just had a major crash on the system that hosts the
angelico-debian-amd64 buildbot, and as usual, checked it carefully
after bringing everything up. It seems now to be timing out after an
hour of operation:

http://buildbot.python.org/all/builders/AMD64%20Debian%20root%203.x/builds/3132/steps/test/logs/stdio

This is happening across all the 3.* branches on my buildbot, but NOT
on 2.7, and not on any other buildbots. That makes it look like some
kind of config problem at my end. In seeking to diagnose it, I
duplicated the 3.x build directory and manually ran the commands to
run a test, and it stalled out (I didn't let it go to the whole hour
but it sat there for some minutes) at the same place: in test_socket.

Running just that test file:

$ ./python Lib/test/test_socket.py
... chomp lots of lines ...
testRecvmsgPeek (__main__.RecvmsgUDP6Test) ...

seems to indicate that the stall is due to IPv6 and UDP. The VM should
have full IPv6 support, although my ISPs don't carry IPv6 traffic, so
it won't be able to reach the internet proper; but it should be able
to do all manner of local tests. The test runs just fine on my main
system, so it's only failing in the buildbot VM. Any ideas as to
what's going on or how to diagnose?

By the way, this looks odd:

make buildbottest TESTOPTS= TESTPYTHONOPTS= TESTTIMEOUT=3600
 in dir /root/buildarea/3.x.angelico-debian-amd64/build (timeout 3900 secs)

The parameter says 3600 (which corresponds to the error message at the
end), but it echoes back that the timeout is 3900 seconds.

ChrisA