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Docker for Rubyists Miami Ruby Brigade Oct. 16, 2017

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Rails in 2005 • Compile Ruby from source • Install Rubygems separately • Choose your own adventure: • CGI (slow) • FastCGI (quite miserable to set up) • App server (fast, low-grade miserable to set up) • Configure database • Figure out gem dependencies

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Rails in 2017 • Choose your own install Ruby adventure • rbenv • chruby • rvm • PPA • source • Configure database • Install dependencies

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Better, Not Great • lotta configuration • need to script it • ideally dev and prod are same

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Configuration Management • Makes setting stuff up repeatable • Good for production • Less-good for development

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Vagrant • Makes setting up a VM repeatable • Good but slow for development • Less common in production

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Docker • Good for development • Good and common in production • Plenty fast • Lots of work is done

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Let's Dockerize Greatjobify

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Greatjobify • Sinatra • ImageMagick

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Greatjobify 1. Pick base image 2. Add OS packages 3. Create and change to app directory 4. Add Gemfile and Gemfile.lock 5. Bundle 6. Add rest of app 7. Run it

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"]

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"] Base image

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"] OS packages

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"] Create and change to app directory

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"] Add Gemfile and Gemfile.lock

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"] Bundle

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"] Add rest of the app

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"] Declare a listening port

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"] Command to run

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Dockerfile FROM ruby:2.4.1 
 RUN apt-get update -qq && \ 
 apt-get install -y build-essential imagemagick 
 RUN mkdir /greatjobify 
 WORKDIR /greatjobify 
 ADD Gemfile* /greatjobify/ 
 RUN bundle install 
 ADD . /greatjobify 
 EXPOSE 9292 
 CMD ["unicorn", "-p", "9292"]

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Building the Image docker build -t greatjobify . Name it "greatjobify"

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And there it is

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Running it docker run --rm -p 9292:9292 -it greatjobify Remove the instance afterwards Forward instance port 9292 to host port 9292 Keep stdio open and hook it up here The image to run

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tfw you don't update your apps more than a couple times per decade

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External Services greatjobify has an optional dependency on memcache

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External Services • Instances can run multiple processes • Instances should be single-purpose • Horizontal scalability • Orchestrate several instances to work together

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Docker Compose "Orchestration"

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docker-compose.yml • Describe each instance that you need • base image or build directory • mounted volumes • dependencies • open ports • commands • environment variables

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web.rb (snippet) memcache_address = ENV['MEMCACHIER_SERVERS'] || 'localhost:11211' 
 memcache = [ 
 memcache_address, 
 { 
 username: ENV['MEMCACHIER_USERNAME'] || nil, 
 password: ENV['MEMCACHIER_PASSWORD'] || nil 
 } 
 ] 
 dalli = Dalli::Client.new *memcache 
 
 use Rack::Cache, 
 :metastore => dalli, 
 :entitystore => dalli

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docker-compose.yml • Web service • Build the current directory • Expose 9292 • Depend on memcached service • Set MEMCACHIER_SERVERS environment variable • Memcached service • Use the "memcached" image

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docker-compose.yml version: '3' 
 services: 
 web: 
 build: . 
 ports: 
 - "9292:9292" 
 depends_on: 
 - memcached 
 environment: 
 - MEMCACHIER_SERVERS=memcached 
 memcached: 
 image: memcached

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Running It docker-compose up

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Rails App • Similar to Sinatra • Web process • Db processes • Support processes • Database console • App console

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Docker in Production • Google Container Engine • AWS Elastic beanstalk • Heroku Container Registry

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Docker in Production • Docker Swarm • Kubernetes