CodeBuild Meets GitHub Actions: A Serverless CI Workflow with Lambda

GitHub Actions provides a powerful CI/CD pipeline, but sometimes you need more control over the environment where your workflows run. AWS CodeBuild now supports Lambda-based self-hosted runners, allowing you to execute GitHub Actions workflows in a cost-efficient, on-demand AWS environment. This guide will walk you through setting up a self-hosted GitHub Actions runner using AWS CodeBuild's Lambda Runner environment.

Prerequisites

Before getting started, ensure you have:

An AWS account with permissions to create CodeBuild projects and Lambda functions
A GitHub repository where you want to run the actions
AWS CLI and GitHub CLI installed on your local machine
An IAM role with necessary permissions for CodeBuild and Lambda execution

Step 1: Create an AWS CodeBuild Project

AWS CodeBuild will serve as our self-hosted GitHub Actions runner. Follow these steps:

1.1 Navigate to AWS CodeBuild

Open the AWS CodeBuild Console
Click Create build project

1.2 Configure Project Settings

Project Name: github-actions-runner
Description: Self-hosted GitHub Actions runner using AWS CodeBuild Lambda Runner

Source: Select GitHub and connect to your repository

1.3 Select Environment

Environment Image: Choose Managed Image
Operating System: Amazon Linux 2
Runtime: AWS Lambda
Compute Type: Lambda Execution Environment
Operating System System: Amazon Linux
Runtime: Python
Image & Version: Select the latest

1.4 Configure IAM Role

Choose New Service Role or select an existing role with permissions to execute CodeBuild, interact with GitHub, and access AWS Lambda.

Attach the following policies if needed:

Click Create Build Project to finalize.

Step 2: Setup the GitHub action workflow.

Navigate to your GitHub repository
Go to Actions tab and create a simple workflow.
To point the lambda self-hosted runner in place, update your .github/workflows/main.yml to use it: Please note the runs-on: section here that you need to at to the workflow file.

Here is a full example of the workflow file.

Push changes to your repository, and the self-hosted runner in AWS CodeBuild will pick up the job and the lambda function will run your job.

2.1 Limitations

Lambda compute is designed for speed, optimizing startup times for builds. However, it does have some limitations and does not support the following use cases:

Reserved Capacity
Caching Across Builds
Restricting Runtime with Timeouts
Tools Requiring Root-User Permissions
Long-Running Builds (Lambda has a maximum timeout of 15 minutes)

Using AWS CodeBuild's Lambda Runner for GitHub Actions provides a scalable, cost-efficient alternative to traditional self-hosted runners. You only pay for execution time, and the Lambda-based environment ensures seamless scaling. Try this setup for your CI/CD workflows and enjoy the flexibility of AWS CodeBuild in your GitHub Actions pipelines!

Happy coding! 🚀

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