Running autopkgtests in the cloud

It’s great to see more and more packages in Debian and Ubuntu getting an autopkgtest. We now have some 660, and soon we’ll get another ~ 4000 from Perl and Ruby packages. Both Debian’s and Ubuntu’s autopkgtest runner machines are currently static manually maintained machines which ache under their load. They just don’t scale, and at least Ubuntu’s runners need quite a lot of handholding.

This needs to stop. To quote Tim “The Tool Man” Taylor: We need more power!. This is a perfect scenario to be put into a cloud with ephemeral VMs to run tests in. They scale, there is no privacy problem, and maintenance of the hosts then becomes Somebody Else’s Problem.

I recently brushed up autopkgtest’s ssh runner and the Nova setup script. Previous versions didn’t support “revert” yet, tests that leaked processes caused eternal hangs due to the way ssh works, and image building wasn’t yet supported well. autopkgtest 3.5.5 now gets along with all that and has a dozen other fixes. So let me introduce the Binford 6100 variable horsepower DEP-8 engine python-coated cloud test runner!

While you can run adt-run from your home machine, it’s probably better to do it from an “autopkgtest controller” cloud instance as well. Testing frequently requires copying files and built package trees between testbeds and controller, which can be quite slow from home and causes timeouts. The requirements on the “controller” node are quite low — you either need the autopkgtest 3.5.5 package installed (possibly a backport to Debian Wheezy or Ubuntu 12.04 LTS), or run it from git ($checkout_dir/run-from-checkout), and other than that you only need python-novaclient and the usual $OS_* OpenStack environment variables. This controller can also stay running all the time and easily drive dozens of tests in parallel as all the real testing action is happening in the ephemeral testbed VMs.

The most important preparation step to do for testing in the cloud is quite similar to testing in local VMs with adt-virt-qemu: You need to have suitable VM images. They should be generated every day so that the tests don’t have to spend 15 minutes on dist-upgrading and rebooting, and they should be minimized. They should also be as similar as possible to local VM images that you get with vmdebootstrap or adt-buildvm-ubuntu-cloud, so that test failures can easily be reproduced by developers on their local machines.

To address this, I refactored the entire knowledge how to turn a pristine “default” vmdebootstrap or cloud image into an autopkgtest environment into a single /usr/share/autopkgtest/adt-setup-vm script. adt-buildvm-ubuntu-cloud now uses this, you shold use it with vmdebootstrap --customize (see adt-virt-qemu(1) for details), and it’s also easy to run for building custom cloud images: Essentially, you pick a suitable “pristine” image, nova boot an instance from it, run adt-setup-vm through ssh, then turn this into a new adt specific “daily” image with nova image-create. I wrote a little script to demonstrate and automate this, the only parameter that it gets is the name of the pristine image to base on. This was tested on Canonical’s Bootstack cloud, so it might need some adjustments on other clouds.

Thus something like this should be run daily (pick the base images from nova image-list):

$ ./ ubuntu-utopic-14.10-beta2-amd64-server-20140923-disk1.img
  $ ./ ubuntu-utopic-14.10-beta2-i386-server-20140923-disk1.img

This will generate adt-utopic-i386 and adt-utopic-amd64.

Now I picked 34 packages that have the “most demanding” tests, in terms of package size (libreoffice), kernel requirements (udisks2, network manager), reboot requirement (systemd), lots of brittle tests (glib2.0, mysql-5.5), or needing Xvfb (shotwell):

$ cat pkglist

Now I created a shell wrapper around adt-run to work with the parallel tool and to keep the invocation in a single place:

$ cat adt-run-nova
#!/bin/sh -e
adt-run "$1" -U -o "/tmp/adt-$1" --- ssh -s nova -- \
    --flavor m1.small --image adt-utopic-i386 \
    --net-id 415a0839-eb05-4e7a-907c-413c657f4bf5

Please see /usr/share/autopkgtest/ssh-setup/nova for details of the arguments. --image is the image name we built above, --flavor should use a suitable memory/disk size from nova flavor-list and --net-id is an “always need this constant to select a non-default network” option that is specific to Canonical Bootstack.

Finally, let’ run the packages from above with using ten VMs in parallel:

parallel -j 10 ./adt-run-nova -- $(< pkglist)

After a few iterations of bug fixing there are now only two failures left which are due to flaky tests, the infrastructure now seems to hold up fairly well.

Meanwhile, Vincent Ladeuil is working full steam to integrate this new stuff into the next-gen Ubuntu CI engine, so that we can soon deploy and run all this fully automatically in production.

Happy testing!