CI/CD for an Elixir + Phoenix LiveView App on Fly.io with GitHub Actions

Compile cleanly, test LiveView against Postgres, and deploy your Phoenix app to Fly.io on every push.

This recipe ships a Phoenix LiveView app to Fly.io. CI compiles with warnings as errors, runs the test suite against a Postgres service container, then deploys with flyctl using a release-stage migration.

What the pipeline does

set up Elixir and OTP
install deps and compile with --warnings-as-errors
run mix test against Postgres
check formatting
deploy to Fly.io with flyctl

The workflow

A Postgres service backs Ecto. MIX_ENV=test compiles strictly. flyctl deploy builds the release image and runs the configured release command for migrations.

.github/workflows/ci.yml

name: CI
on:
  push:
    branches: [main]
  pull_request:
jobs:
  test:
    runs-on: ubuntu-latest
    services:
      postgres:
        image: postgres:16
        env:
          POSTGRES_PASSWORD: postgres
          POSTGRES_DB: app_test
        ports: ["5432:5432"]
        options: >-
          --health-cmd "pg_isready" --health-interval 10s
          --health-timeout 5s --health-retries 5
    env:
      MIX_ENV: test
      DATABASE_URL: ecto://postgres:postgres@localhost:5432/app_test
    steps:
      - uses: actions/checkout@v4
      - uses: erlef/setup-beam@v1
        with:
          elixir-version: "1.17"
          otp-version: "27"
      - run: mix deps.get
      - run: mix compile --warnings-as-errors
      - run: mix format --check-formatted
      - run: mix test
  deploy:
    needs: test
    if: github.ref == 'refs/heads/main'
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: superfly/flyctl-actions/setup-flyctl@master
      - run: flyctl deploy --remote-only
        env:
          FLY_API_TOKEN: ${{ secrets.FLY_API_TOKEN }}

Caching and speed

Cache deps and _build with actions/cache keyed on mix.lock and the OTP/Elixir versions. Clean compiles plus LiveView tests take time; cheaper managed runners such as Latchkey (around 69% cheaper than GitHub-hosted) keep the suite fast and auto-retry a flaky hex.pm fetch.

Deploying

Generate a scoped deploy token with flyctl tokens create deploy and store it as FLY_API_TOKEN. Add a [deploy] release_command = "/app/bin/migrate" to fly.toml so Ecto migrations run before the new release takes traffic.

Key takeaways

Compile with --warnings-as-errors so warnings fail CI.
Run Ecto and LiveView tests against a Postgres service container.
Run migrations via a Fly release_command before traffic shifts.