Docker: What It Is and Why You Should Care

A brief explanation of what Docker actually is and instructions for setting up a Rails dev environment in Docker.

Transcript

1. Docker
   What It Is and Why You Should Care
   

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2. My Story
   

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3. What is Docker?
   Virtualization
   

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6. =
   Virtual Machines
   Guest
   Host
   

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7. =
   Docker Containers
   

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8. That’s all great.
   Why should I care?
   

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9. • Install Homebrew
   • brew install several packages - SQL, Imagemagick
   • Install RVM or Rbenv
   • Install one or more versions of Ruby
   • Clone one or more Git repos
   • Run bundle/npm/bower/etc install for each repo
   

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10. • Start the db server (unless it’s always running)
    • Start the rails app
    • Background workers? Sidekiq and Redis
    • SoA? Need to start those up too on the right port
    • iTerm or Tmux setup to run all this? Foreman?
    • Foreman requires same directory. Subcontractor.
    

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12. • Install Docker
    • Clone your Git repos
    • Place your docker-compose.yml file
    

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13. • docker-compose up
    

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14. =
    Dev Dev
    

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15. =
    Dev CI
    

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16. ≈
    Dev Prod
    

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17. Where do I start?
    

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18. Background:
    Building Blocks
    

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19. Background
    Tools
    

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20. • Dockerfile
    • docker-compose.yml
    

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21. Docker Engine - Dockerfile
    

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22. FROM ruby:2.3.1-slim
    RUN apt-get update -qq && apt-get install -y \
    build-essential libpq-dev postgresql-client
    ENV RAILS_ROOT /var/www/myapp
    RUN mkdir -p $RAILS_ROOT/tmp/pids
    WORKDIR $RAILS_ROOT
    COPY Gemfile Gemfile
    COPY Gemfile.lock Gemfile.lock
    RUN gem install bundler
    RUN bundle install
    

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23. Docker Compose YAML
    

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24. app:
    build: .
    command: rails server --port 3000 --binding 0.0.0.0
    environment:
    RAILS_ENV: development
    DATABASE_HOST: db
    links:
    - db
    ports:
    - 3000:3000
    volumes:
    - .:/var/www/myapp
    db:
    image: postgres:9.5.3
    environment:
    POSTGRES_USER: username
    POSTGRES_PASSWORD: password
    volumes:
    - myapp-db:/var/lib/postgresql/data
    

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25. sidekiq:
    build: .
    command: bundle exec sidekiq
    environment:
    REDIS_URL: redis://redis:6379
    links:
    - db
    - redis
    volumes:
    - .:/var/www/myapp
    redis:
    image: redis
    

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26. Dockerfile
    docker-compose.yml
    

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27. Other Ways To Get Started
    

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29. Takeaways
    • Docker reduces dev dependencies
    • It adds parity where it is used (Dev-CI-Production)
    • Easy to get started
    

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30. Questions?
    

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31. • Alexander Clark
    • Twitter @atheclark
    • Blog http://alexander-clark.com/blog
    • Github alexander-clark
    • Slack alexander-clark
    

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32. Thanks for listening.
    

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