Codespace on Rails

Why?

I've been trying to get some Ruby on Rails projects I have set up on Codespaces. After many tries, I've finally got it working (at least the way I wanted it to), so now I'm creating this repository to keep these changes and copy them to other projects whenever needed.

I mostly copied what was done here and fixed some things that were not working for me or that I didn't need.

How?

1. Copy the .devcontainer folder to your project
2. Copy .env.example to .env and customize environment variables
3. Customize the files to your needs
4. Open the project in Codespaces

What's in the box?

• Ruby 3.4.4
• PostgreSQL 17 (exposed locally on port 5433)
• Valkey 8 (Redis-compatible, exposed locally on port 6379)
• Node LTS
• ZSH and Oh My Zsh
• Mise version manager
• Non root user

Security & Performance Features

This configuration includes several security and performance improvements:

Security

• Environment-based credentials: Database and Redis passwords use environment variables
• Valkey authentication: Password protection enabled by default
• Pinned versions: All Docker images and features use specific versions
• Non-root user: Runs as vscode user for better security

Performance & Reliability

• Service dependencies: App waits for database and Redis to be healthy before starting
• Health checks: Robust health monitoring with proper startup periods
• Resource limits: Memory limits prevent resource exhaustion (PostgreSQL: 512M, Valkey: 128M)
• Optimized volumes: Named volumes with explicit drivers for better persistence

Customizations

There are a couple of things you can customize and a couple of things you should customize.

Could

You can choose different Ruby and Node versions by updating the devcontainer.json file. Currently, it will install Ruby 3.4.x and Node LTS You can also change the PostgreSQL username and password, although I don't think it matters too much.

You can also change the project's name under devcontainer.json and docker-compose.yml if you want to. I've left it as Your Project Name for now.

If you change the service name (defaults to app right now), remember to update the app section in docker-compose.yml. They have to match.

Should

You should, however, update your database.yml file if you use one. Here is what mine looks like:

default: &default
  adapter: postgresql
  encoding: unicode
  host: postgres # This is the name of the container in the docker-compose.yml file
  username: postgres # This is the default username for the postgres image
  password: postgres # This is the default password for the postgres image
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

development:
  <<: *default
  database: app_development

test:
  <<: *default
  database: app_test

production:
  <<: *default
  url: <%= ENV["DATABASE_URL"] %>

Notice the host: postgres? That's the name of the container in the docker-compose.yml file. If you change it to db, you must update the database.yml file too.

Environment Variables

This devcontainer configuration supports customization through environment variables. Copy .env.example to .env and adjust the values as needed:

Database Configuration

• POSTGRES_USER: PostgreSQL username (default: postgres)
• POSTGRES_DB: PostgreSQL database name (default: postgres)
• POSTGRES_PASSWORD: PostgreSQL password (default: postgres)

Valkey/Redis Configuration

• VALKEY_PASSWORD: Valkey password (default: devpassword)
• VALKEY_PORT: Host port for Valkey (default: 6379)

Rails Configuration

• RAILS_ENV: Rails environment (default: development)
• SECRET_KEY_BASE: Rails secret key base
• RAILS_MASTER_KEY: Rails master key for credentials

Service Connection Examples

Connecting to Valkey (Redis) from Rails

Configure in config/application.rb or an initializer:

# config/initializers/redis.rb
Redis.current = Redis.new(
  host: 'valkey',  # Service name from docker-compose.yml
  port: 6379,
  password: ENV['VALKEY_PASSWORD'] || 'devpassword'
)

Using with Rails cache:

# config/environments/development.rb
config.cache_store = :redis_cache_store, {
  url: "redis://:#{ENV['VALKEY_PASSWORD'] || 'devpassword'}@valkey:6379/0"
}

Using with Sidekiq:

# config/initializers/sidekiq.rb
Sidekiq.configure_server do |config|
  config.redis = {
    url: "redis://:#{ENV['VALKEY_PASSWORD'] || 'devpassword'}@valkey:6379/0"
  }
end

Sidekiq.configure_client do |config|
  config.redis = {
    url: "redis://:#{ENV['VALKEY_PASSWORD'] || 'devpassword'}@valkey:6379/0"
  }
end

Connecting to PostgreSQL from Rails

Your database.yml should use the service name and environment variables:

default: &default
  adapter: postgresql
  encoding: unicode
  host: postgres
  username: <%= ENV['POSTGRES_USER'] || 'postgres' %>
  password: <%= ENV['POSTGRES_PASSWORD'] || 'postgres' %>
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

How do I SSH into the Codespace instance?

This configuration includes an SSH server. To access your codespace instance, you should install the gh CLI and run gh codespace ssh and select your codespace.

How do I attach to my container if I'm not using Codespaces?

docker exec -it --user vscode app /bin/zsh

or

devcontainer exec --workspace-folder . zsh

(or use DevContainer VSCode extension)

Using devcontainer CLI

Install with npm install -g @devcontainers/cli

Setting it up

devcontainer up --workspace-folder .

Checking for outdated dependencies

devcontainer --workspace-folder . outdated

Upgrading your dependencies

devcontainer upgrade --workspace-folder .

Removing everything

docker stop $(docker ps -q)
docker system prune -a --volumes --force