Fedora-Infra / loopabull-tasks

Created a year ago
Maintained by pingou
The loopabull tasks/playbook of the Fedora Infrastructure
Members 4

loopabull-tasks

loopabull is an event loop driven Ansible playbook execution engine.

In other words, it triggers Ansible playbooks automatically when receiving a corresponding fedmsg message.

This repository stores the ansible playbooks and their related scripts used by the Fedora Infrastructure team.

Adding a new task

Adding a new task to loopabull is quite easy.

  • Figure out which fedmsg topic you want to trigger off
  • Create a playbook named after the topic
  • Create a role doing the action you want to have triggered of this topic
  • Configure loopabull to listen to this topic
  • Push the new loopabull configuration

For example, let's run a small/dummy python script everytime a koji build finished in staging.

The topic we want to trigger of is thus: org.fedoraproject.stg.buildsys.build.state.change, so we go and edit the playbook: playbooks/org.fedoraproject.stg.buildsys.build.state.change.yml in this repository and add a debug role that has one variable: the message received via fedmsg msg. Then add a debug role in playbooks/roles/debug. Make that role install your python script, call it with a certain environment variable and print the output of the script for debugging.

Then, on the infrastructure's ansible repository, configure loopabull to listen to this topic (line 70): https://infrastructure.fedoraproject.org/cgit/ansible.git/tree/playbooks/groups/loopabull.yml?id=4b053dd68cc12e1823516eec481fab04f9b9166b#n70

Finally, run the ansible playbook deploying this change:

ansible-playbook /srv/web/infra/ansible/playbooks/groups/loopabull.yml -t loopabull

Note

you may have to restart things on loopabull's side:

systemctl restart loopabull loopabull@1 loopabull@2 loopabull@3 loopabull@4 loopabull@5

For every change made to this repository (for example when fixing typos, bugs or making improvements), the playbooks/groups/loopabull.yml playbook from the Fedora infrastructure's ansible repo will need to be run so the underlying clone of this repo on the system gets updated.

Good Practice

  • Keep in mind that a playbook run locally and can be ran by multiple workers simultaneously, therefore it is advised to keep all blocking tasks out of this repository (for example: avoid installing packages, install them via the playbooks/groups/loopabull.yml playbook in infra's ansible repo.)
  • Do not have your script return a non-zero error code. If a playbook fails (returns a non-zero return code) loopabull will stop the worker. So use the non-zero return code carefully so as to not kill all the workers and break loopabull
  • Passing JSON blobs to a shell script can be tricky, especially with regards to the quotes used. Imaging a fedmsg messages containing itself some JSON fields (we do have some), you quickly end up with a mix of single-quote ' and double-quotes ". The proper way to pass the message to the script avoiding issues with quotes is to use: {{ msg | to_json | quote }} (note the lack of quotes surrounding this, | quote takes care of adding them).