CH1.md

Chapter 1 - Hello World

GitHub Actions is a continuous integration and continuous deployment (CI/CD) platform that allows you to automate your build, test, and deployment pipelines. It gives you the ability to create workflows that build and test every pull request to your repository, and then later automatically deploy merged pull requests to production.

GitHub Actions also supercharges DevOps by allowing you to run workflows triggered by a large number of different events in your repository. As an example, you can build a workflow which automatically adds the appropriate labels (e.g. "bug" or "triage") whenever someone creates a new issue in your repository.

GitHub provides Linux, Windows, and macOS virtual machines to run your workflows, or you can host your own self-hosted runners in your own data center or cloud infrastructure.

The components of GitHub Actions

GitHub Actions workflows are always triggered by events occurring in your repository such as a pull request being opened or an issue being created. A workflow contains one or more jobs which can run in sequential order or in parallel. Each job will run inside its own virtual machine runner, or inside a container, and has one or more steps. Each step executes either a shell script or an action, which is a reusable extension that automates a certain piece of your workflow.

You can read more about GitHub Actions and workflows components in the official documentation.

1 - Implement your first workflow with GitHub Actions

1.1 - Create a "Hello World" workflow

Enough talking. Let's create our very first GitHub Actions workflow!

1. In your repository, click on the Actions tab. You will be offered a list of workflow suggestions. For your first workflow, however, you need to click the set up a workflow yourself link at the top of the page.

2. This will automatically bring you to the GitHub Web GUI Action Editor, which prompts you to create a new file in your repository under .github/workflows/main.yml. Paste the following content into it:

   name: Hello World Training Workflow
   
   on:
     workflow_dispatch:
   
   jobs:
     greet:
       runs-on: ubuntu-latest
       steps:
         - name: Greet the User
           run: echo "Hello World!"

   

3. Click on Commit changes and then commit it directly to the main branch (we won't tell anyone 🤫).

   

Rename the file to hello.yml, click Start Commit and commit it directly to the main branch.

1.2 - Run the workflow manually

The workflow you created is triggered by the workflow_dispatch event, meaning it can be manually executed:

on:
  ...
  # Allows you to run this workflow manually from the Actions tab
  workflow_dispatch:

You can manually execute your workflow by navigating to the Actions tab, selecting your desired workflow, and clicking on the Run workflow button:

Refresh the page or wait a few seconds to see the results of your workflow run.

Congratulations, you have just run your first GitHub Actions workflow. 🥳

About workflow triggers

Your workflows are only triggered by the events you specify. For more information, see "Configuring a workflow" and "Workflow syntax for GitHub Actions". We will learn more about this shortly.

1.3 - Analyze your workflow

In the list of workflow runs, click on one of the runs for the "Hello World" workflow. You will be shown its single job (greet) under "Jobs" on the left side of the page. Click on that job to view its logs (you can expand the logs for a particular step by clicking on it).

The workflow run view also allows you to re-run jobs in case problems occurred (button on the top right). Additionally, re-running a job allows you to enable debug logging.

2 - Use an action

Using bash commands to automate processes is a fundamental requirement for any CI/CD system. However, writing shell scripts can become very cumbersome as you scale, and you might find yourself rewriting the same functionality across different projects.

Fortunately, GitHub Actions offers a much better way to handle automation: by using actions! An action is a small, composable, and reusable unit of automation code that can be easily integrated into all of your workflows.

2.1 - Add an action to your workflow

Let's start by using one of the most basic yet commonly used actions to gain an understanding: The actions/checkout action:

1. In your editor, navigate to the Code tab, then to .github/workflows/hello.yml, and then click the little pencil icon in the top right corner to reopen the actions editor.

2. Add the following steps to the existing job:

   steps:
     - name: Greet the User
       run: echo "Hello World!"
     # List all files in the current directory for comparison before and after actions/checkout@v2.
     - run: ls -l
     - uses: actions/checkout@v2
     - run: ls -l

   Note that, unlike running shell commands, running an action requires the use of the uses keyword.

3. Commit the changes and trigger a new workflow run.

2.2 - Understand the power of Actions

If you examine the workflow logs and compare the output of the two ls -l commands, you will notice that the actions/checkout Action has checked out the main branch of our repository onto the runner. And it accomplished this without requiring you to specify any git clone shell command or any references or configurations.

This is just the tip of the iceberg. There are thousands of even more sophisticated actions available for you to use, which can turn complex automations into a matter of a few lines of configuration. We will explore many of these throughout this workshop.

Next:

• Chapter 2