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Use More Performant Runners

This guide describes how to use higher-performance runners for your build and build-all GitHub Actions. OpenCraft uses Blacksmith, a drop-in replacement for GitHub-hosted runners.

Prerequisites

  • The Blacksmith GitHub App must be installed for your GitHub organization. Blacksmith is available for organizations only, not personal repositories.
  • Your cluster must have been created from the Launchpad cluster template with the build workflows.

Changing the Runner Label

The build and build-all workflows use a RUNNER_WORKFLOW_LABEL input that controls which runner executes the jobs. By default, clusters use ubuntu-latest (GitHub-hosted runners). To use Blacksmith, set the label to a Blacksmith runner tag such as blacksmith-8vcpu-ubuntu-2404. We use blacksmith-8vcpu-ubuntu-2404 as it provides a reasonably fast build for the MFE and platform as well.

Option 1: Set Default When Creating a New Cluster

When generating a new cluster with cookiecutter, choose a Blacksmith runner for runner_workflow_label instead of ubuntu-latest, use the runner label you wish to use.

Option 2: Edit Workflow Defaults in Your Cluster Repository

For existing clusters, edit the workflow files in your cluster repository to change the default value of RUNNER_WORKFLOW_LABEL:

  1. In your cluster repo (e.g. open-craft/launchpad-my-cluster), open .github/workflows/build.yml and .github/workflows/build-all.yml.

  2. Change the default for the RUNNER_WORKFLOW_LABEL input from ubuntu-latest (or self-hosted) to a Blacksmith runner tag, for example:

RUNNER_WORKFLOW_LABEL:
  description: 'The label of the runner workflow to run'
  required: false
  default: "blacksmith-8vcpu-ubuntu-2404"  # Blacksmith: 8 vCPU, 32 GB, Ubuntu 24.04
  type: string
  1. Commit and push. All future build and build-all runs will use Blacksmith unless overridden when manually triggering a workflow.

Option 3: Override When Manually Triggering

When you run the Build or Build All Images workflow from the GitHub Actions UI (workflow_dispatch), you can override the runner label by changing the RUNNER_WORKFLOW_LABEL input to blacksmith-8vcpu-ubuntu-2404 (or another Blacksmith tag) before starting the run. This does not require editing any files.

Blacksmith Runner Tags (OpenCraft Example)

OpenCraft typically uses the following Blacksmith runners for Docker builds:

Runner Tag vCPU Memory Use Case
blacksmith-2vcpu-ubuntu-2404 2 8 GB Quick, light builds
blacksmith-8vcpu-ubuntu-2404 4 16 GB Standard Open edX image builds
blacksmith-8vcpu-ubuntu-2404 8 32 GB Faster builds, heavier images
blacksmith-16vcpu-ubuntu-2404 16 64 GB Large or parallelized builds

For Ubuntu 22.04, use the ubuntu-2204 variants (e.g. blacksmith-4vcpu-ubuntu-2204). See the Blacksmith Instance Types documentation for the full list.

Other Workflows Using Runners

The create-instance, update-instance, and delete-instance workflows also accept RUNNER_WORKFLOW_LABEL. If you want those to use Blacksmith as well, edit their defaults in your cluster repo in the same way as for build and build-all.

See Also