Scaling Runners in GitHub Actions

Introduction

Scaling runners in GitHub Actions is essential for optimizing CI/CD workflows. Runners are the servers that execute your workflows. Understanding how to scale them effectively can lead to faster builds, reduced wait times, and better resource management.

Key Concepts

Self-hosted Runners: These are runners that you manage, allowing for customization and resource optimization.
GitHub-hosted Runners: These are provided by GitHub, offering a simplified setup but with limited control.
Concurrency: This refers to the ability to run multiple jobs at the same time, which can be scaled based on the number of available runners.
Scaling Options: You can scale by increasing the number of runners or by enhancing the resources (CPU, memory) of the existing runners.

Note: Self-hosted runners can be scaled horizontally (adding more machines) or vertically (upgrading existing machines).

Configuring Runners

To scale runners effectively, you need to configure them correctly. Below are the steps to set up self-hosted runners:

Navigate to your repository on GitHub.
Go to Settings > Actions > Runners.
Click on Add runner.
Select the operating system of your runner.
Follow the instructions to download and configure the runner application.
Start the runner application on your server.

Important: Make sure your server meets the necessary requirements and has network access to GitHub.

Example Configuration

./config.sh --url https://github.com/[owner]/[repo] --token [token] --name [runner_name]

Best Practices

Monitor your runner usage and performance using GitHub Insights.
Automate the scaling process based on job queue times.
Use labels to manage which jobs run on specific runners.
Regularly update your runner software for security and performance improvements.

FAQ

What is the difference between self-hosted and GitHub-hosted runners?

Self-hosted runners are managed by you, offering more control and customization, while GitHub-hosted runners are managed by GitHub with less setup effort required.

How can I increase the concurrency of my jobs?

You can increase concurrency by adding more runners or by configuring your workflows to run jobs in parallel.

Scaling Runners Flowchart


                graph TD;
                    A[Start] --> B{Is the job queue length > threshold?};
                    B -- Yes --> C[Increase runner count];
                    B -- No --> D{Is performance satisfactory?};
                    D -- No --> E[Review resource allocation];
                    D -- Yes --> F[End];