Rails development environment powered by Nix + Direnv

.envrc

use flake

# Use binstubs directly
PATH_add bin

# Web server port
export PORT=3000

# MySQL config directory
export MYSQL_HOME=./config

dev

### Location: bin/dev

#!/usr/bin/env sh

exec foreman start -f Procfile.dev "$@"

flake.nix

{
  description = "dev environment";
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
  inputs.flake-utils.url = "github:numtide/flake-utils";

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let pkgs = nixpkgs.legacyPackages.${system};
      in with pkgs; {
        devShells.default = mkShell {
          packages = [
            # Runtimes
            ruby_2_7
            nodejs-16_x

            # Databases
            mysql80
            redis

            # Tools
            chromedriver
            imagemagick
            yarn

            # Dependencies
            cmake
            icu
            libffi
            libiconv
            openssl
            pkg-config
            zlib
            zstd
          ];

          shellHook = ''
            MYSQL_DATA_DIR=$PWD/mysql_data
            MYSQL_SOCKET_FILE=mysql.sock

            # Initialize MySQL data directory
            if [ ! -d "$MYSQL_DATA_DIR" ]; then
              mkdir -p $MYSQL_DATA_DIR

              mysqld --initialize-insecure \
                --datadir=$MYSQL_DATA_DIR \
                --socket=$MYSQL_SOCKET_FILE
            fi

            # Create database.yml if not present
            DATABASE_FILE=$PWD/config/database.yml
            if [ ! -f "$DATABASE_FILE" ]; then
              cp -v config/database.yml.example $DATABASE_FILE
            fi

            # Create my.cnf if not present
            MYSQL_CONFIG_FILE=$PWD/config/my.cnf
            if [ ! -f "$MYSQL_CONFIG_FILE" ]; then
              cp -v config/my.cnf.example $MYSQL_CONFIG_FILE
            fi

            # Create Procfile.dev if not present
            PROCFILE=$PWD/Procfile.dev
            if [ ! -f "$PROCFILE" ]; then
              cp -v Procfile.example $PROCFILE
            fi
          '';
        };
      });
}

my.cnf

### This file is located in ./config/my.cnf

[client]
port=3306
socket=./mysql_data/mysql.sock

[mysqld]
port=3306
bind-address=127.0.0.1
datadir=./mysql_data
socket=mysql.sock
character-set-server=utf8mb4
collation-server=utf8mb4_unicode_ci

Procfile.dev

web: bundle exec puma -C ./config/puma.rb
mysql: mysqld
redis: redis-server
js: ./bin/webpacker -w
dj: bundle exec rake jobs:work
sidekiq: bundle exec sidekiq -C config/sidekiq.yml

Requirement

• Nix (Package management in a different way)
• Direnv (Setup development env according to shell.nix when entering the project's root directory)

Steps

1. Enable direnv

direnv allow

All necessary packages for development are installed and the MySQL data directory is created in ./mysql_data.

2. Install gems

bundle install

3. Start to dev with Procfile.dev

dev

That's all. Open http://localhost:3000 to visit.

You may need to setup database in another shell:

bundle exec rails db:setup

Enjoy the power of functional programming and plain old shell script!

mysqld is already in the Procfile?

@alper Yes, it is contained in the mysql80 package. All packages are installed once direnv is enabled via direnv allow.

I mean:

In one shell, start MySQL server

I don't think you have to start it separately if it's in the procfile?

@alper You're right, one can start MySQL with Procfile and then create database. Thank you.