This post will briefly describe how I did a TDD update to Opscode’s runit to resolve an issue reported last night.

First, the issue manifests itself only on Debian systems. The runit cookbook’s runit_service provider will write an LSB init.d script on Debian, rather than symlinking to /usr/bin/sv. The problem raised in the new ticket is that the template will follow the link and write to /usr/bin/sv. This is bad, as it will end up in a forkbomb as runsvdir attempts to restart sv on all the things. Oops! Sorry about that. Let’s get it fixed, and practice some TDD.

The runit cookbook includes support for test-kitchen, though I did need to update it for this effort. Part of this change was adding a box for Debian in the .kitchen.yml. I set about resolving this with TDD in mind.

First, the runit cookbook includes a couple “test” cookbooks to facilitate setting up the system with the runit_service resource so the outcome can be tested to ensure the behavior is correct. I started by adding a “failing test” in the runit_test::service recipe, meaning a link resource, and a runit_service resource that would overwrite /usr/bin/sv.

link "/etc/init.d/cook-2867" do
  to "/usr/bin/sv"

runit_service "cook-2867" do
  default_logger true

Then I ran kitchen test on the Debian box. As expected, the link was created, and then the runit service was configured. The service’s provider will wait until the service is up. Since we’ve destroyed the sv binary, that will never happen, so I destroyed it. I manually confirmed the behavior too, to make sure I wasn’t seeing something weird. Due to its very nature, this is really hard to test for automatically, but it will happen consistently.

Next, I had to write the code to implement the fix for this bug. Essentially, this means checking if the /etc/init.d/cook-2867 file is a symbolink link, and removing it.

initfile = ::File.join( '/etc', 'init.d', new_resource.service_name)
::File.unlink(initfile) if ::File.symlink?(initfile)

Simple enough. Next I tested again by destroying the existing environment and rerunning it from scratch. This takes some time, but it verifies that everything is working properly. Here’s the output on Debian:

INFO: Processing link[/etc/init.d/cook-2867] action create (runit_test::service line 147)
INFO: link[/etc/init.d/cook-2867] created
INFO: Processing service[cook-2867] action nothing (dynamically defined)
INFO: Processing runit_service[cook-2867] action enable (runit_test::service line 151)
INFO: Processing directory[/etc/sv/cook-2867] action create (dynamically defined)
INFO: Processing template[/etc/sv/cook-2867/run] action create (dynamically defined)
INFO: Processing directory[/etc/sv/cook-2867/log] action create (dynamically defined)
INFO: Processing directory[/etc/sv/cook-2867/log/main] action create (dynamically defined)
INFO: Processing directory[/var/log/cook-2867] action create (dynamically defined)
INFO: Processing file[/etc/sv/cook-2867/log/run] action create (dynamically defined)
INFO: Processing template[/etc/init.d/cook-2867] action create (dynamically defined)
INFO: template[/etc/init.d/cook-2867] updated content
INFO: template[/etc/init.d/cook-2867] owner changed to 0
INFO: template[/etc/init.d/cook-2867] group changed to 0
INFO: template[/etc/init.d/cook-2867] mode changed to 755
INFO: runit_service[cook-2867] configured
INFO: Chef Run complete in 7.267132764 seconds
INFO: Running report handlers

I didn’t feel I needed a specific test for this in minitest-chef, because it wouldn’t have finished converging (earlier behavior I saw in the “failing” test).

If you’re contributing to cookbooks, and they have support for test-kitchen, it’s awesome if you can open a bug report with a failing test. In this case, it was fairly easy to reproduce the bug.