How GitHub Actions can turn your code into a Docker daemon

# the default task runs rake test standard
bundle exec rake

# the name can be anything you want, but try not to change it once you push it to Github
name: Ruby

on:
  # this runs on each push...
  push:
    # ...to this list of branches, which is just main
    branches:
      - main

  # also runs on each pull request
  pull_request:

jobs:
  # this is the "pipeline" that does the business
  build:
    # this is the name of the kind of runner that Github hosts
    runs-on: ubuntu-latest
    # each job has a name, too. the bits next to "matrix" means "run one job for each combination of things in the strategy.matrix structure"
    name: Ruby ${{ matrix.ruby }}
    strategy:
      matrix:
        ruby:
          # we are only testing Ruby 3.2.2, but it could be easily changed to support more versions
          - '3.2.2'

    steps:
    # you have to check out the code first, this is almost always the first step in a GHA job
    - uses: actions/checkout@v3
    # this installs Ruby, since the base runner does not have Ruby
    - name: Set up Ruby
      uses: ruby/setup-ruby@v1
      with:
        # magic sauce for the matrix jobs to substitute the values in the combinations
        ruby-version: ${{ matrix.ruby }}
        # use a cache. it saves a ton of time.
        bundler-cache: true
    # this runs the tests
    - name: Run the default task
      run: bundle exec rake

# we make an image from the default Ruby version tag for our version of Ruby
FROM ruby:3.2.2

# this directory comes from the base image and is where we will deploy the app
# it is common practice to use a simple and non-FHS directory in the root
WORKDIR /srv

# important! we do this specifically for caching. if these files do not change,
# then later builds will re-use the cache! it can sometimes take minutes to
# install dependencies, so this is an excellent optimization
COPY Gemfile Gemfile.lock feed2gram.gemspec .

# this app requires this file to calculate the version
COPY lib/feed2gram/version.rb lib/feed2gram/

# install dependencies
# so long as the files in the prior COPY statements do not change, then this
# step will be cached on subsequent builds and save potentially _minutes_
RUN bundle install

# just copy everything, even the files we already copied
ADD . .

# this makes every invocation of the container work like a command-line tool
# any arguments to `docker run` will be passed to the application just
# like you would on the command line
ENTRYPOINT ["/srv/exe/feed2gram"]

git clone https://github.com/searls/feed2gram
cd feed2gram
docker build -t feed2gram .
# wait for the build to finish
docker run --rm -it \ # --rm removes and -it allows it to work like a CLI tool
  -v my-config.yml:/srv/config.yml \ # this bind-mounts the config-you-have-made into the container
  feed2gram \ # name of the docker image
  --config /srv/config.yml # arguments passed to the entrypoint

name: Ruby

on:
  push:
    branches:
      - main

  pull_request:

jobs:
  build:
    runs-on: ubuntu-latest
    name: Ruby ${{ matrix.ruby }}
    strategy:
      matrix:
        ruby:
          - '3.2.2'

    steps:
    - uses: actions/checkout@v3
    - name: Set up Ruby
      uses: ruby/setup-ruby@v1
      with:
        ruby-version: ${{ matrix.ruby }}
        bundler-cache: true
    - name: Run the default task
      run: bundle exec rake

  # 👇New job is here!
  docker:
    runs-on: ubuntu-latest
    name: Build Docker Container
    # this job will only run if all of the "needs" are successful
    # hence, tests must pass!
    needs: [build]
    steps:
      - uses: actions/checkout@v4
      # we install qemu to build arm images
      - uses: docker/setup-qemu-action@v3
      # configure buildkit
      - uses: docker/setup-buildx-action@v3
      # log into github container registry if not a pull request
      - uses: docker/login-action@v3
        if: github.event_name != 'pull_request'
        with:
          registry: ghcr.io
          username: searls
          # 👇Github container registry requires a personal access token
          # Don't commit this to code, ever.
          password: ${{ secrets.CH_PAT }}
      # this does all the work for us
      - uses: docker/build-push-action@v5
        with:
          # 👇Important! you want to use a cache to save CI minutes
          cache-from: type=gha
          # mode=max means "also cache intermediate layers and not just the resulting image"
          # which is the part that makes the prior optimizations worth while
          cache-to: type=gha,mode=max
          context: .
          # build for both amd64 and arm64, for the mac/raspberrypi folks!
          platforms: linux/amd64,linux/arm64
          # 👻 we don't push the resulting image if this is a pull request
          push: ${{ github.event_name != 'pull_request' }}

#!/usr/bin/env bash
# ☝️ this is the preferred method of running bash.
# not everyone has /bin/bash
# and not every /bin/bash is the same (macos 🤢)

echo "Starting feed2gram daemon..."

# run the app once
# the "$@" will pass all of the arguments given to the container to the
# original script, so it's 💯 compatible with the old implementation!
exe/feed2gram --verbose "$@"

# sleep by default 60 seconds
# or define env var SLEEP_TIME=XXX to pick a different interval
while sleep ${SLEEP_TIME:-60} ; do

  # run it again, with a timestamp output
  echo "[$(date -R)] Re-running feed2gram..."
  exe/feed2gram --verbose "$@"
done

docker run --rm -it
  -e SLEEP_TIME=600 \ # 🛏️ this is how you change the sleep interval
  -v my-config.yml:/srv/my-config.yml \
  feed2gram \
  --config /srv/my-config.yml

docker run --rm -it \
  --entrypoint /srv/exe/feed2gram \ # 👈 this is all you need
  -v my-config.yml:/srv/my-config.yml \
  feed2gram \
  --config /srv/my-config.yml

andrew@potassium:~/feed2gram$ docker images feed2gram
REPOSITORY   TAG       IMAGE ID       CREATED          SIZE
feed2gram    latest    881fe940ab29   45 seconds ago   1.04GB

andrew@potassium:~/feed2gram$ docker images ruby
REPOSITORY   TAG            IMAGE ID       CREATED       SIZE
ruby         3.2.2          e1ebac6c7119   6 days ago    988MB

FROM ruby:3.2.2-alpine
# 👆The alpine image is much more spartan,
# but it's more than enough for our little application

WORKDIR /srv
COPY Gemfile Gemfile.lock feed2gram.gemspec ./
COPY lib/feed2gram/version.rb lib/feed2gram/

# 👇 the dependencies are different in alpine
RUN apk update && \
    apk add autoconf bash git gcc make musl-dev && \
    bundle install && \
    apk del --purge --rdepends git gcc autoconf make musl-dev
ADD . .

# 👇 this is where persistent data lives
VOLUME /config

# 👇 the volume subtly changes the default arguments
CMD ["--config", "/config/feed2gram.yml"]

ENTRYPOINT ["/srv/bin/daemon"]

andrew@potassium:~/feed2gram$ docker images feed2gram
REPOSITORY   TAG       IMAGE ID       CREATED         SIZE
feed2gram    latest    dc054fbec1a7   5 seconds ago   132MB

name: Ruby

on:
  push:
    branches:
      - main
    # 👇 we run this workflow on tags that start with a "v"
    tags:
      - 'v*'

  pull_request:

jobs:
  build:
    runs-on: ubuntu-latest
    name: Ruby ${{ matrix.ruby }}
    strategy:
      matrix:
        ruby:
          - '3.2.2'

    steps:
    - uses: actions/checkout@v3
    - name: Set up Ruby
      uses: ruby/setup-ruby@v1
      with:
        ruby-version: ${{ matrix.ruby }}
        bundler-cache: true
    - name: Run the default task
      run: bundle exec rake

  docker:
    runs-on: ubuntu-latest
    name: Build Docker Container
    needs: [build]
    steps:
      - uses: actions/checkout@v4
      - uses: docker/setup-qemu-action@v3
      - uses: docker/setup-buildx-action@v3
      # 👇 here is the new action
      - uses: docker/metadata-action@v5
        id: metadata
        with:
          images: |
            ghcr.io/searls/feed2gram            
          tags: |
            type=raw,value=latest,enable={{is_default_branch}}
            type=ref,event=pr
            type=semver,pattern={{version}}
            type=semver,pattern={{major}}.{{minor}}
            type=semver,pattern={{major}},enable=${{ !startsWith(github.ref, 'refs/tags/v0.') }}
            type=sha,prefix=,format=long            
      - uses: docker/login-action@v3
        if: github.event_name != 'pull_request'
        with:
          registry: ghcr.io
          username: searls
          password: ${{ secrets.CH_PAT }}
      - uses: docker/build-push-action@v5
        with:
          cache-from: type=gha
          cache-to: type=gha,mode=max
          context: .
          platforms: linux/amd64,linux/arm64
          push: ${{ github.event_name != 'pull_request' }}
          # 👇 here we use the outputs to magic all of this work away
          tags: ${{ steps.metadata.outputs.tags }}
          labels: ${{ steps.metadata.outputs.labels }}