[Buildbot-devel] getting buildslaves to exit after one build?

[Dan Kegel]

How does one configure a buildslave to exit after one build job?

Short story: I'm running the buildslave inside a container, I start
a fresh container for each build, and I can't use the existing libvirt support.

Long story:

I'm updating a buildbot config at a shop I just joined, and I see they're
making system configuration changes during the build.   chroot jails
immediately spring to mind.  Turns out, though, that at least on a
couple recent flavors of Linux, lxc is far enough along that it's
kind of the preferred way of creating chroot-jail-like things.
And various groups have been using lxc with buildbot for some time
(including canonical, which uses them in their testing infrastructure, see e.g.
https://dev.launchpad.net/yellow/ParallelTestingSetupForDataCentre )

Now, you can use lxc via libvirt, see e.g.
https://wiki.ubuntu.com/SergeHallyn_libvirtlxc
for how easy that can be.  So you might think that buildbot's existing libvirt
integration is the way to go.  But I have a couple concerns about
using libvirt to control lxc containers for buildbot:
- unless your lxc images are stored on lvm, cloning images can be slow
(though maybe this is ok, really small images only take 5 seconds to
lxc-create once cached)
- libvirt doesn't have a way of tapping into lxc-start-ephemeral
(though maybe this is ok)
- libvirt can only create lxc containers on the local machine as far as I know
- according to http://sourceforge.net/mailarchive/forum.php?thread_name=20120824173521.GA18199%40amd1&forum_name=lxc-users
libvirt-lxc is due to be replaced once lxc's liblxc api is finalized
So, at least for the moment, libvirt isn't quite the way to go for lxc
buildslaves.