GitHub Actions uses events to automatically start workflows in your repository. These events can be tied to everything from code changes to direct manual actions. Here’s a step-by-step look at how events initiate workflows:

1. Define Workflow Triggers:
   In your workflow YAML, use the on declaration to specify which events should activate your workflow.

   on:
     push:
       branches:
         - main
     pull_request:
       types: [opened, synchronize]
     schedule:
       - cron: '0 2 * * 1'
     workflow_dispatch:
   
       

2. Single Event Activation:
   Workflows can run when a single trigger occurs, such as a code push or a pull request.
3. Multiple Events Handling:
   List more than one event to allow your workflow to respond to different triggers.

   on: [push, pull_request]
       

4. Use Filters for Specificity:
   Apply branch, path, tag, or activity type filters to fine-tune workflow activation. For example, you can trigger jobs only when files in the src/ directory change.

   on:
     push:
       branches:
         - 'main'
       paths:
         - 'src/**'
   
       

5. Manual and External Triggers:
   - workflow_dispatch: Start workflows on-demand from the GitHub UI.
   - repository_dispatch: Allow external systems to trigger workflows via the GitHub API.

By leveraging these event types and filters, you can orchestrate CI/CD processes that fit your project’s needs, ensuring workflows run exactly when required.

GitHub Actions offers a variety of events that can start workflows automatically. Understanding these common triggers helps you choose the right events to automate your CI/CD processes effectively. Here’s a breakdown of frequently used events and their typical use cases:

1. Push:
   Triggers when commits or tags are pushed to a repository.
   Use case: Running CI builds, code linting, or triggering deployments after code changes.
2. Pull Request:
   Triggers on PR lifecycle events like opened, synchronized (updated), or closed.
   Use case: Running tests and validation to ensure PR quality before merging.
3. Schedule:
   Triggers on a cron-based schedule defined by time and frequency.
   Use case: Performing routine maintenance tasks or generating reports regularly.
4. workflow_dispatch:
   Enables manual triggering of workflows via the GitHub UI.
   Use case: On-demand deployments or tasks that require human initiation.
5. repository_dispatch:
   Allows external systems to trigger workflows through the GitHub API.
   Use case: Integrations with external tools or automation triggered outside GitHub.
6. Issue and Label Events:
   Triggers on activities related to issues or labels, like opened, closed, or labeled.
   Use case: Automating issue triage or managing labels for better project tracking.
7. workflow_run:
   Triggers when another workflow completes.
   Use case: Chaining workflows such as starting deployment after successful tests.

By selecting the appropriate trigger events, you can tailor your workflows to respond promptly and accurately to the activities relevant to your project.

GitHub Actions lets you customize when workflows run using filters. These options help your automation run only for the changes or branches you care about. Here’s how to use filters with a step-by-step approach:

1. Branch Filtering:
   Restrict workflow runs to specific branches. This is helpful when you want actions only for production or development.

   on:
     push:
       branches:
         - main
         - 'releases/**'
     pull_request:
       branches:
         - develop
   
       

   This example triggers jobs only on pushes to main or any branch under releases/, and for pull requests targeting develop.
2. Excluding Branches:
   Prevent workflows from running on certain branches.

   on:
     push:
       branches-ignore:
         - 'feature/**'
   
       

   Here, the workflow is skipped for branches with names starting with feature/.
3. Tag Filtering:
   Limit workflow triggers to tags for actions like versioned releases.

   on:
     push:
       tags:
         - 'v1.*'
   
       

   This runs the workflow only when pushing tags starting with v1..
4. Path Filtering:
   Start workflows only when certain files or directories are changed.

   on:
     push:
       paths:
         - 'src/**'
         - '!src/tests/**'
   
       

   This triggers on changes inside the src/ folder, except for files under src/tests/.
5. Excluding Paths:
   Ignore specific file or folder changes so that workflows aren’t triggered.

   on:
     push:
       paths-ignore:
         - 'docs/**'
   
       

   The workflow will not run when changes are made only to files in the docs/ directory.
6. Activity Type Filtering:
   Narrow down triggers based on specific actions, like a PR being opened or labeled.

   on:
     pull_request:
       types: [opened, labeled]
   
       

   This only triggers the workflow when a pull request is opened or labeled.

Combining these filters gives you control over when CI/CD processes start, making your workflows faster and focused on the most relevant changes.

GitHub Actions gives you the power to run workflows in more advanced ways, allowing you to create custom automations beyond the standard push or pull request events. This flexibility is perfect for integrating external tools or building sophisticated CI/CD pipelines. Follow these steps to use advanced and custom events in your workflows:

1. Manual Workflow Runs:
   Trigger workflows directly from the GitHub interface using workflow_dispatch. You can also define input fields for user customization.

   on:
     workflow_dispatch:
       inputs:
         environment:
           description: 'Environment to deploy to'
           required: true
           default: 'production'
   
       

   With this setup, you can select the workflow, provide input, and start it by hand.
2. Custom External Triggers:
   Start workflows from outside GitHub using repository_dispatch. This is useful when you want external systems, scripts, or webhooks to kick off automation.

   on:
     repository_dispatch:
       types: [external_update]
   
       

   You can trigger this using an API call. This lets you pass custom data to the workflow for detailed or dynamic automation.
3. Custom Payload Handling:
   When triggering with repository_dispatch, include a payload for use in your workflow, such as flags or messages.

   {
     "event_type": "external_update",
     "client_payload": {
       "service": "monitoring",
       "status": "alert"
     }
   }
   
       

   Access this data within your workflow using the expression github.event.client_payload.service.
4. Chaining Workflows:
   Use the workflow_run event to link workflows so one runs after another completes. This is helpful for deployment steps that should only happen after tests finish.

   on:
     workflow_run:
       workflows: ["CI Tests"]
       types:
         - completed
   
       

   This ensures stages in your pipeline execute in sequence.
5. Building Custom Actions:
   For the most flexibility, create your own actions that run scripts, call APIs, or perform automation tailored to your infrastructure.
   • Write actions in YAML, JavaScript, or Docker.
   • Define inputs, outputs, and conditions for when the custom action runs.
   • Use your custom actions in any workflow just like built-in actions.

Leveraging advanced and custom events lets you build automation workflows that fit precisely with your development and deployment lifecycle, ensuring your CI/CD system is both powerful and adaptable.

Maximize the benefits of GitHub Actions by applying proven practices that streamline your workflows, increase security, and keep your automation maintainable. Follow these step-by-step tips to build an efficient CI/CD pipeline:

1. Limit Workflow Scope with Filters:
   Use branch, path, and event type filters to run workflows only when necessary. This avoids wasted runs and keeps pipelines responsive.

   on:
     push:
       branches: [main]
       paths: ['infra/**']
   
       

2. Cancel Redundant Runs:
   Apply the concurrency setting to automatically cancel in-progress jobs when a new run is triggered for the same branch or tag.

   concurrency:
     group: ${{ github.ref }}
     cancel-in-progress: true
   
       

3. Use Caching for Faster Builds:
   Take advantage of caching (like dependencies or build outputs) to speed up repeated jobs and reduce runtime in your workflows.

   - uses: actions/cache@v4
     with:
       path: ~/.npm
       key: ${{ runner.os }}-npm-${{ hashFiles('**/package-lock.json') }}
       restore-keys: |
         ${{ runner.os }}-npm-
   
       

4. Set Up Secrets and Environments:
   Store sensitive data in GitHub Secrets and organize jobs using environments to safely partition access and approval.
   • Restrict who or what can approve deployments to production.
   • Control access to API tokens, service credentials, and other secrets.
5. Use Conditional Logic for Flexible Runs:
   Write if expressions within jobs or steps to run actions only in specific cases, such as deploying from certain branches or acting on labeled pull requests.

   if: github.ref == 'refs/heads/main' && github.event_name == 'push'
   
       

6. Reuse Workflows and Steps:
   Employ reusable workflows and action templates to standardize processes and promote maintainability across repositories.

   jobs:
     call-standard:
       uses: org/.github/.github/workflows/test-template.yml@main
   
       

7. Monitor, Test, and Improve:
   Regularly review workflow logs, add status badges, and iterate on your automation for reliability and speed.
   • Visualize workflow status with badges in your README.
   • Make tweaks based on failure patterns or bottlenecks.

Applying these techniques leads to secure, reliable, and efficient CI/CD processes that scale smoothly as your infrastructure and development requirements evolve.