Actions Cost Optimization

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Scenario 1 — macOS cost problem

1. Gate expensive macOS jobs so they only run when necessary
   • Keep fast, cross-platform checks (lint, unit tests) running on every push to give developers quick feedback.
   • Restrict the macOS job to run only for pull requests targeting main (or only on main itself), using a job-level if: condition.

# .github/workflows/ios-ci.yml
on:
  push:
  pull_request:

jobs:
  linux-tests:
    name: "Linux unit & lint"
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Install dependencies
        run: npm ci
      - name: Run unit tests
        run: npm test

  macos-tests:
    name: "macOS integration & iOS tests"
    runs-on: macos-latest
    # Only run on pull requests targeting the main branch
    if: github.event_name == 'pull_request' && github.event.pull_request.base.ref == 'main'
    steps:
      - uses: actions/checkout@v4
      - name: Install CocoaPods
        run: pod install
      - name: Run iOS integration tests
        run: xcodebuild test -workspace MyApp.xcworkspace -scheme MyApp -destination 'platform=iOS Simulator,name=iPhone 14'

2. Consider self-hosted macOS runners for heavy, repeatable workloads
   • Migrate frequent macOS work to self-hosted machines (on-prem Mac minis or cloud macOS instances) to eliminate per-minute GitHub billing for those jobs.
   • Self-hosted runners can dramatically flatten your Actions bill for macOS-heavy teams, but they introduce operational responsibilities.

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Scenario 2 — Windows runner costs

1. Audit and move cross-platform steps to Linux
   • If the tasks are language/runtime-agnostic (Node.js, Python, standard Docker containers, etc.), run them on ubuntu-latest instead of Windows. Linux runners are the cost baseline and usually faster to provision.

2. Gate Windows-only jobs to main or PRs targeting main
   • For steps that truly require Windows (e.g., .NET Framework-only tests, Windows-specific tooling), restrict their execution using an if: condition so they do not run on every feature-branch push.

jobs:
  windows-build:
    name: "Windows build & tests"
    runs-on: windows-latest
    # Only run on the main branch
    if: github.ref == 'refs/heads/main'
    steps:
      - uses: actions/checkout@v4
      - name: Setup .NET
        uses: actions/setup-dotnet@v4
        with:
          dotnet-version: '8.0.x'
      - name: Build and test
        run: dotnet test

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Quick reference: costs and actions

• Run cheap, cross-platform steps on ubuntu-latest.
• Use on: triggers and job-level if: conditions (github.event_name, github.ref, github.event.pull_request.base.ref) to limit expensive jobs to relevant branches or PRs.
• Prefer fast feedback for developers by keeping lint/unit checks on every push and gating slow/integration tests.
• Evaluate self-hosted runners when usage is predictable and heavy; plan for maintenance and security.

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Links and further reading

• GitHub Actions: https://docs.github.com/actions
• Self-hosted runners: https://docs.github.com/actions/hosting-your-own-runners
• Workflow syntax & if expressions: https://docs.github.com/actions/using-workflows/workflow-syntax-for-github-actions