Github CI/CD

Github’s CI/CD platform is broken into 2 units: Github Actions and reusable workflows.

Describing workflows and actions makes them sound like the same thing (or very similar), and to an extent they are. I will let Github’s documentation explain this in-depth, but the short version is that a reusable workflow is a set of “jobs” to automate code actions like linting, building, releasing, etc, and they can be chained together. An action (or “reusable component”) is like a CI/CD component package that a workflow can call to handle a very specific step, like cloning a repository or installing Node.js (or other languages).

Official Actions are stored in the Github Actions repository, but anyone can create an action in their own repository. The Github Actions platform is strict about where actions and workflows must live; you cannot call an action or workflow from a path outside of .github/. This means that whether your reusable actions or workflows are stored in the repo that calls them, or a centralized repository with all of your pipeline components, they must exist under a specific path:

• .github/workflows/ for reusable workflows
• .github/actions/ for reusable components

There are some other differences between actions and workflows. Actions do not use a jobs: section, meaning you can’t create a multi-stage actions (you would have to use a workflow for that). Additionally, actions cannot inherit or use secrets, where workflows can. This design is intentional; the idea is that a workflow is made up of a series of action calls, while each action handles 1 very specific task/process. A reddit user named /u/queen-adreena summed it up perfectly: “An action is a song. A workflows is a playlist”.

Github provides a repository of reusable workflows that help with the development of action components.