Github actions compilation/caching issues

Hey folks!

Been through it all with elixir compilation. We were using Concourse for a bit, which allowed me to run images that had our application pre-compiled. I would rsync the files into the cloned branch, and only the changed files would compile.

For many reasons we moved to github actions, and since then I have been unable to create a setup that doesn’t compile/get dependencies every time. We also have issues with branches that change our structure.sql file, as the test runs depend on seeding a database, and new relations tend to not be applied unless we we “bust the cache” by incrementing a version number in the build cache string.

This all has created the headache of using up our minutes quite rapidly as our team (or a pull request) grows, and dipping deeply into our actions overage budget.

Below is part of a sample action

jobs:
  ingest:
    runs-on: ubuntu-18.04
    services:
      redis:
        image: redis
        options: >-
          --health-cmd "redis-cli ping"
          --health-interval 10s
          --health-timeout 5s
          --health-retries 5
        ports:
          - 6379:6379
      postgres:
        image: postgres:11.5
        env:
          POSTGRES_USER: postgres
          POSTGRES_PASSWORD: postgres
          POSTGRES_DB: postgres
        ports:
          - 5432:5432
        options: --health-cmd pg_isready --health-interval 10s --health-timeout 5s --health-retries 5

    steps:
    - uses: actions/checkout@v2

    - name: Setup elixir
      uses: erlef/setup-elixir@v1
      with:
        elixir-version: ${{ env.ELIXIR_VERSION }}
        otp-version: ${{ env.OTP_VERSION }}

    - name: Retrieve Mix Dependencies Cache
      uses: actions/cache@v2
      id: mix-cache
      with:
        path: backend/deps
        key: ${{ env.OTP_VERSION }}-${{ env.ELIXIR_VERSION }}-test-deps-cache-{{ hashFiles('**/mix.lock') }}
        restore-keys: |
          ${{ env.OTP_VERSION }}-${{ env.ELIXIR_VERSION }}-test-deps-cache-
    - name: Retrieve Build Cache
      uses: actions/cache@v2
      id: build-cache
      with:
        path: backend/_build/**
        key: ${{ env.OTP_VERSION }}-${{ env.ELIXIR_VERSION }}-app-build-cache-v5-${{ hashFiles('**/mix.lock','**/structure.sql') }}
        restore-keys: |
          ${{ env.OTP_VERSION }}-${{ env.ELIXIR_VERSION }}-app-build-cache-v5-
    - name: Install Mix Dependencies
      run: |
        cd backend/
        mix local.rebar --force
        mix local.hex --force
        MIX_ENV=test mix deps.get
    - name: Compile Dependencies
      if: steps.build-cache.outputs.cache-hit != 'true'
      run: |
        cd backend
        MIX_ENV=test mix compile
    - name: Run Tests
      run: |
        cd backend/
        MIX_ENV=test mix ecto.reset
        mix cmd --app app mix test --color

Other examples I’ve found around the forums don’t seem to improve anything.

Does anything stand out here? How can I make these not get deps/compile on every run?

Finally, we also split our tests up so that each have their own actions file. If a PR is open and X app has files changed, the related action runs. If multiple apps have changes, those tests run. Our main package, all of the tests run. Is there possibly a way for a PR to not run all of these tests if a subsequent commit to that PR doesn’t change the apps that have already been tested?

Happy to share more details/clarify, apologies for any longwindedness or confusion.

Just as a note, we have 35 test actions / 24 apps in an umbrella, hence the complicated actions setup. Perhaps a root of some of our problems.

Probably try replacing that with uses: erlef/setup-beam@v1? That’s the only thing that kind of stands out to me because in our projects that’s what we use for our GitHub actions setup.

Thanks for your input, we still end up compiling our applications on every run.

The following combination of steps ensures there is no recompilation happening in my case

 - name: Set up Elixir
        uses: erlef/setup-beam@v1
        with:
          elixir-version: ${{ matrix.elixir }} # Define the elixir version [required]
          otp-version: ${{ matrix.otp }} # Define the OTP version [required]

- name: Restore elixir dependencies cache
        id: mix-cache
        uses: actions/cache@v2
        with:
          path: deps
          key: ${{ runner.os }}-mix-${{ matrix.otp }}-${{ matrix.elixir }}-${{ hashFiles('**/mix.lock') }}

 - name: Restore build cache
        id: build-cache
        uses: actions/cache@v1
        with:
          path: _build
          key: cache-${{ runner.os }}-dialyzer_build-${{ matrix.otp }}-${{ matrix.elixir }}-${{ hashFiles('**/mix.lock') }}

      - name: Install Mix Dependencies
        if: steps.mix-cache.outputs.cache-hit != 'true'
        run: |
          mix local.rebar --force
          mix local.hex --force
          mix deps.get

      - name: Compile
        if: steps.build-cache.outputs.cache-hit != 'true'
        env:
          MIX_ENV: test
        run: mix deps.compile; mix compile --force --warnings-as-errors

I also had the two caches combined into one in the past, which worked just as well.

Note that I also do a --warnings-as-errors here for an additional check.

The differences to your setup that I’m seeing are,

  • no structure.sql in the hash
  • i use matrix, not env for versioning
  • my build path is just _build, not _build/**
  • all the critical steps run in test env using the env option in the config