Optimistic Builds™ with Kamal

deploy.yml

# Optimistic Builds for Kamal
#
# This workflow speeds up deploys by building the Docker image in parallel with CI.
# Instead of: CI → Build → Deploy (sequential)
# We do: CI ↘
#              → Deploy
#        Build ↗
#
# The "optimistic" part: we start building before knowing if tests pass.
# Since CI usually passes, this saves ~2 minutes per deploy.

name: Deploy

on:
  push:
    branches: [main]

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

jobs:
  test:
    runs-on: ubuntu-latest
    # Your normal CI setup here
    steps:
      - uses: actions/checkout@v4
      # ... your test steps

  # Build Docker image in parallel with tests (optimistic build)
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      - name: Set up SSH for Kamal
        uses: webfactory/[email protected]
        with:
          ssh-private-key: ${{ secrets.SSH_PRIVATE_KEY }}

      - name: Set up Ruby
        uses: ruby/setup-ruby@v1
        with:
          bundler-cache: true

      # Build and push image to your registry
      - name: Build and push image
        env:
          KAMAL_REGISTRY_PASSWORD: ${{ secrets.KAMAL_REGISTRY_PASSWORD }}
          VERSION: ${{ github.sha }}
        run: bundle exec kamal build push --version=$VERSION

      # Pre-pull image on the server so deploy is instant
      - name: Pre-pull image on server
        env:
          KAMAL_REGISTRY_PASSWORD: ${{ secrets.KAMAL_REGISTRY_PASSWORD }}
          VERSION: ${{ github.sha }}
        run: bundle exec kamal build pull --version=$VERSION

  # Deploy only runs after BOTH test and build succeed
  deploy:
    needs: [test, build]
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Set up SSH for Kamal
        uses: webfactory/[email protected]
        with:
          ssh-private-key: ${{ secrets.SSH_PRIVATE_KEY }}

      - name: Set up Ruby
        uses: ruby/setup-ruby@v1
        with:
          bundler-cache: true

      # Deploy the pre-built, pre-pulled image
      # --skip-push: Don't build/push, image already exists
      # --version: Use the specific image we built earlier
      - name: Deploy
        env:
          KAMAL_REGISTRY_PASSWORD: ${{ secrets.KAMAL_REGISTRY_PASSWORD }}
          VERSION: ${{ github.sha }}
        run: bundle exec kamal deploy --skip-push --version=$VERSION