Docker for Rails Developers: Notes for Rails 6.1, Ruby 2.7.2

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I thought that there might be interest in using the book with Rails 6.1 and Ruby 2.7.2. I’ll note what I needed to do differently here.

  • p. 11 rails new myapp --skip-test. Do not add the --skip-bundle flag–it causes several steps of the new command to fail. (Notably, webpacker:install doesn’t occur.)
  • p. 19 Update the Dockerfile to get a newer version of Ruby, a recent version of yarn, and set up webpacker:
    FROM ruby:2.7.2 # Ensure latest packages for Yarn RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | APT_KEY_DONT_WARN_ON_DANGEROUS_USAGE=true apt-key add - RUN echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list RUN apt-get update -yqq RUN apt-get install -yqq --no-install-recommends nodejs yarn WORKDIR /usr/src/app COPY . . RUN bundle install RUN yarn install
  • p. 40 Modified Dockerfile after The Gemfile Caching Trick:
    FROM ruby:2.7.2 # Ensure latest packages for Yarn RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | APT_KEY_DONT_WARN_ON_DANGEROUS_USAGE=true apt-key add - && \ echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list && \ apt-get update -yqq && apt-get install -yqq --no-install-recommends \ nodejs \ yarn WORKDIR /usr/src/app COPY Gemfile* ./ RUN bundle install RUN yarn install COPY . . CMD ["bin/rails", "s", "-b", "0.0.0.0"]
  • p. 88 In Rails JavaScript Front End with Webpacker, nothing needs to be done to install webpacker, since we installed it at the beginning. (There is no issue with the version of node, either. In fact, running the curl to get an “up-to-date” version ends up installing a deprecated version.) You do need to install the webpacker React integration, though–docker-compose run web bin/rails webpacker:install:react.
  • p. 96 Setting Up RSpec, grab a newer version of RSpec–gem 'rspec-rails', '~> 4.0.1'–per the rspec-rails installation instructions.
  • p. 96-97 I had to stop, build, and up -d --force-recreate the webpack_dev_server after doing the same for web, after installing RSpec.
  • p. 100 gem 'capybara', '~> 3.34'
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  • p. 146 With Rails 6, there’s a new way to handle secrets. Instead of defining SECRET_KEY_BASE, you’ll need to define RAILS_MASTER_KEY.
    1. Run bin/rails credentials:edit and save the result. This will create the value of an encryption key in config/master.key and an encrypted secrets file in config/credentials.yml.enc.
    2. Copy the value of the encryption key in config/master.key to the RAILS_MASTER_KEY environment variable in .env/production/web. (SECRET_KEY_BASE is obsolete–don’t define it.)
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