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Working With Docker

This repository offers experimental support support for developing using Docker, if you're interested. Docker is not required to work on this gem.

The docker compose approach should link to enough of your networking configuration that you can release the gem. However, you have to do some of the configuration yourself, because it's dependent on your host operating system.

Set-Up

Put your personal and OS-specific configuration in a compose.override.yml file.

The following instructions work for an Ubuntu host, and will probably work for other common Linux distributions. Add a compose.override.yml in the local directory, that looks like this:

version: '3.3'

# https://blog.giovannidemizio.eu/2021/05/24/how-to-set-user-and-group-in-docker compose/

services:
  shell:
    # You have to set the user and group for this process, because you're going to be
    # creating all kinds of files from inside the container, that need to persist
    # outside the container.
    # Change `1000:1000` to the user and default group of your laptop user.
    user: 1000:1000
    volumes:
      - /etc/passwd:/etc/passwd:ro
      - ~/.gem/credentials:/app/.gem/credentials:ro
      # $HOME here is your host computer's `~`, e.g. `/home/reid`.
      # `ssh` explicitly looks for its config in the home directory from `/etc/passwd`,
      # so the target for this has to look like your home directory on the host.
      - ~/.ssh:${HOME}/.ssh:ro
      - ${SSH_AUTH_SOCK}:/ssh-agent
    environment:
      - SSH_AUTH_SOCK=/ssh-agent

You may have to change the 1000:1000 to the user and group IDs of your laptop. You may also have to change the version parameter to match the version of the docker compose.yml file.

Adapting the above compose.override.yml for MacOS should be relatively straight-forward. Windows users, I'm afraid you're on your own. If you figure this out, a PR documenting how to do it would be most welcome.

Running

Start the containers:

docker compose up -d

You may need to install or update the gems:

docker compose exec -it shell bundle install

To get a shell in the container:

docker compose exec -it shell /bin/bash

Once in the shell:

cd demo
bundle exec rails test:system

Note that this system test approach is highly experimental and has some rough edges. The docker compose file and/or steps to run system tests may change. The tests currently fail, because the files with which they're being compared were generated on a Mac, but the Docker containers are running Linux.

Troubleshooting Docker

  • With the above configuration, the gems are kept in vendor/bundle on your hosts, which is $GEM_HOME or /app/vendor/bundle in the running Docker container. If you're having permission problems when switching versions of Ruby or Rails, you can try sudo rm -rf vendor/bundle on the host, then run BUNDLE_GEMFILES=gemfiles/7.0.gemfile bundle update in the Docker container to re-install all the gems with the right permissions.
  • Sometimes, on shutdown, the Rails server PID file isn't removed, and so the above will fail. rm demo/tmp/pids/server.pid will fix it.