Sinatra on Nix

Example Sinatra project using Nix to configure it.

Prerequisites

• Nix 1.11+

Getting Started

$ cd path/to/this/clone
$ ./devenv
$ bundle install --path=.bundle

To start the Puma server running the App Sinatra web application and redis-server:

$ env RACK_ENV=bench0 bundle exec foreman start

In another terminal you can run benchmark via wrk:

$ ./bench
...

Note that all the following are installed:

• Ruby v2.3.1p112
• Redis v3.0.7
• Bundler v1.12.5
• wrk (mystery meat 2012 version because Go projects just are this way?)

Plus all of their transitive dependencies. Every time you run ./devenv with the pinned channel (peek inside the script devenv) you will get the exact same binaries on your OS/Arch pair, every time.

This is the power of Nix.

Package Definition

See Ruby Nix package definition (default.nix) for an example of how we would specify a Nix expression for the distributable dependencies for the application. We build the Puma Rubygems dependency with native Ruby/C setup.

Shell/Development Environment Definition

See Development environment definition (shell.nix) to see how we can write a Nix expression to specify a fully bootstrappable (only requirement is Nix tooling available in currently environment, nothing else) development environment.

We could have started off this project with the command line approximation of a dev environment for this project like so:

nix-shell -p ruby bundler bundix

This would have brought into scope the ruby tooling to get us started without a Nix expression initially.

Then we would have proceeded as Ruby developers with common startup steps for initializing a Ruby project like so:

$ echo "source 'https://rubygems.org'" > Gemfile
$ echo  >> Gemfile
$ echo "gem 'sinatra'"  >> Gemfile
# More dependencies
$ bundle package --path .bundle
# Generate gemsets.nix expression with dependencies included
$ bundix -d

Bundix is just a Nix expression encapsulating the dependencies defined in the Gemfile* files maintained/generated in accordance with the bundler tooling.

More information on managing Ruby projects can be found here: http://nixos.org/nixpkgs/manual/#sec-language-ruby

What's Next?

So what else can we do? Oh, I am so glad you asked...

• Define Docker images using the same deterministic build/dependency management tooling Nix provides. See README.md here.

TODO:

• AMI image example
• Virtualbox image example