Rails on Nix

This is an exploration of setting up vanilla Rails apps using the Nix package manager.

I'm using an Ubuntu VM via Vagrant to ensure the environment is as isolated as possible from my own local environment (MacOS).

Step-by-step instructions

Install Vagrant & VirtualBox

In the local (MacOS) environment:

brew cask install vagrant
brew cask install virtualbox

Clone the repo

In the local (MacOS) environment:

git clone git@github.com:floehopper/rails-on-nix.git

Start & provision the VM

In the local (MacOS) environment:

cd rails-on-nix
vagrant up

• Provisioning the VM takes quite a while!

• Installs the Nix package manager.

• For each Rails app (rails-postgres-app & rails-mysql-app):

  • Uses a generated Gemfile and ephemeral Nix shells to generate the Gemfile.lock, gemset.nix & shell.nix files to make the appropriate version of the Rails gem, its dependent gems, and its dependent OS packages available.
  • From within the Nix shell specified by the gemset.nix & shell.nix files generated in the previous step, generates a new Rails app.
  • Within the Rails app sub-directory, uses ephemeral Nix shells to generate the Gemfile.lock, gemset.nix & shell.nix files to make the gems bundled in the Rails app, their dependent gems, and their dependent OS packages available.
  • Within the Rails app sub-directory, from within the Nix shell specified by the gemset.nix & shell.nix files generated in the previous step:
    • installs OS packages which are runtime dependencies for the Rails app: node.js, yarn & ruby_x_y
    • also installs appropriate database OS package
    • runs rails yarn:install or rails webpacker:install depending on the major version of Rails
    • sets up and starts database server
    • generates simple "blog" using scaffold
    • creates & migrates the databases
    • runs the tests
    • runs the Rails server in the background

View websites

rails-postgres-app

• View http://localhost:3000/ in your browser.
• View http://localhost:3000/posts to see generated "blog" pages.

rails-mysql-app

• View http://localhost:3001/ in your browser.
• View http://localhost:3001/posts to see generated "blog" pages.

Notes

Accessing the Rails app environment on the VM

On your local machine, run:

vagrant ssh

On the VM, run:

cd $RAILS_APP_NAME
nix-shell

Provisioning the VM multiple times

Most of the provisioning operations are fairly idempotent, but I haven't tested this thoroughly.

Further work

• Multiple Rails apps requiring different versions of Bundler.

• Investigate using direnv/lorri in conjunction with nix to seamlessly move between different Rails app directories. See: https://github.com/direnv/direnv/wiki/Nix.

• Investigate using Nix home-manager to provide a more generic environment on the VM to create the Rails app, i.e. run rails new.

• Investigate using Nix to make node.js packages available instead of yarn.