After using Azure DevOps Yaml Pipelines for some time now I wanted to learn more about Github’s Actions.

Introduction

According to the Github documentation, GitHub Actions makes it easy to automate all your software workflows, with world-class CI/CD.

Sounds interesting, let’s explore more about Github Actions in this blog post.

Github Action terminology

Before we dive into the Github Actions we first need to know more about the terminology used when working with Github Actions.

Workflows

Workflows are custom automated processes that you can set up in your repository to build, test, package, release, or deploy any project on GitHub.

Workflow jobs

A workflow job is a defined task made up of steps.

Workflow runs

A workflow run is an instance of your workflow that runs when the pre-configured event occurs.

Runners

The runner is the application that runs a job from a GitHub Actions workflow. The runner can run on the hosted machine pools or run on self-hosted environments.

Actions

Actions are individual tasks that you can combine to create jobs and customize your workflow. You can create your own actions, and use and customize actions shared by the GitHub community.

Marketplace

GitHub Marketplace is a central location for you to find actions created by the GitHub community.

You can discover new actions from the workflow editor on GitHub, and from the GitHub Marketplace page.

Get started

To get started with Github actions go to your Github Account open or create a new Repository and click on Actions tab.

If you select the simple workflow you get below Hello World workflow.

name: CI

on: [push]

jobs:
  build:

    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v1
    - name: Run a one-line script
      run: echo Hello, world!
    - name: Run a multi-line script
      run: |
        echo Add other actions to build,
        echo test, and deploy your project.

Let’s change this to a Hello World PowerShell version which can be triggered via a external webhook:

name: Hello World

on: [repository_dispatch]

jobs:
  hello-world:

    runs-on: windows-latest

    steps:
    - uses: actions/checkout@v1
    - name: Run PowerShell Hello World script
      if: github.event.action == 'inline'
      run: Write-Output 'Hello World!'
    - name: Run a multi-line PowerShell script
      if: github.event.action == 'inline'
      run: |
        $psversiontable;
        Get-Process;

Result when above Github Action workflow is run:

Explanation of Workflow

Trigger Github Action from webhook

By using the repository_dispatch type of trigger we can trigger the Github Actions via a Webhook.

To be able to trigger a Github Action from a webhook you need to create a Personal Access Token under Developer Settings.

After storing the Github Personal Access Token as environment variable you can use this token in the web request.

<#
    Triggering Github Actions from a webhook call
#>

#region variables
$GithubToken = $env:githubtoken # Personal Access Token stored as environment variable
$GithubUserName = 'stefanstranger'
$GithubRepo = 'githubactions'
#endregion

$uri = ('https://api.github.com/repos/{0}/{1}/dispatches' -f $GithubUserName, $GithubRepo)

#region web request call
$Body = @{
    'event_type' = 'inline' #used in the if condition of the Github Action
} | ConvertTo-Json


$params = @{
    ContentType = 'application/json'
    Headers     = @{
        'authorization' = "token $($GithubToken)"
        'accept'        = 'application/vnd.github.everest-preview+json'
    }
    Method      = 'Post'
    URI         = $Uri
    Body        = $Body
}
  
Invoke-RestMethod @params -verbose
#endregion

If you run above PowerShell script it should trigger the earlier configured Github Action.

Run a PowerShell script stored in your Repository

Instead of an inline PowerShell script we can also use a PowerShell script from our Repository.

Check the following Hello-World.ps1 example script.

If we want to run this script from our Github Action we can create the following Github Action.

name: Hello World script

on: [repository_dispatch]

jobs:
  hello-world-script:

    runs-on: windows-latest

    steps:
    - uses: actions/checkout@v1
    - name: Run PowerShell Hello World script
      if: github.event.action == 'script'
      run: pwsh -command ".\$GITHUB_WORKSPACE\Hello-World.ps1"

Result:

In my next blog post I want to investigate the Github Marketplace and explain how to develop and publish Github Actions.

References:

• Github Actions documentation
• Help documentation Github Action
• A curated list of awesome things related to GitHub Actions
• Workflow syntax for GitHub Actions
• Github repo used for blog post