Rails 8 does not include redis by default in the dev container.

A development container (or dev container for short) allows us to use a container as a full-featured development environment.

It can be used to run an application, to separate tools, libraries, or runtimes needed for working with a codebase, and to aid in continuous integration and testing.

The dev containers can be run locally or remotely, in a private or public cloud, in a variety of supporting tools and editors.

Before

Rails 7.2 ships with dev containers as an opt-in feature.

Adding dev container on a new rails app

rails new <app_name> --devcontainer

Adding dev container to an existing rails app

bin/rails devcontainer

The .devcontainer folder includes everything needed to boot the app and do development in a remote container.

The container setup includes:

A redis container for Kredis, ActionCable etc.
A database (SQLite, Postgres, MySQL or MariaDB)
A Headless chrome container for system tests
Active Storage configured to use the local disk and with preview features working

Here is the default .devcontainer/compose.yaml

name: "app_name"

services:
  rails-app:
    build:
      context: ..
      dockerfile: .devcontainer/Dockerfile

    volumes:
    - ../..:/workspaces:cached

    # Overrides default command so things don't shut down after the process ends.
    command: sleep infinity

    networks:
    - default

    # Uncomment the next line to use a non-root user for all processes.
    # user: vscode

    # Use "forwardPorts" in **devcontainer.json** to forward an app port locally.
    # (Adding the "ports" property to this file will not forward from a Codespace.)
    ports:
    - 45678:45678
    depends_on:
    - selenium
    - redis

  selenium:
    image: seleniarm/standalone-chromium
    restart: unless-stopped
    networks:
    - default

  redis:
    image: redis:7.2
    restart: unless-stopped
    networks:
    - default
    volumes:
    - redis-data:/data

  
volumes:
  redis-data:

Here is the default .devcontainer/devcontainer.json

// For format details, see https://aka.ms/devcontainer.json. For config options, see the
// README at: https://github.com/devcontainers/templates/tree/main/src/ruby
{
  "name": "app_name",
  "dockerComposeFile": "compose.yaml",
  "service": "rails-app",
  "workspaceFolder": "/workspaces/${localWorkspaceFolderBasename}",

  // Features to add to the dev container. More info: https://containers.dev/features.
  "features": {
    "ghcr.io/devcontainers/features/github-cli:1": {},
    "ghcr.io/rails/devcontainer/features/activestorage": {},
    "ghcr.io/rails/devcontainer/features/sqlite3": {}
  },

  "containerEnv": {
    "CAPYBARA_SERVER_PORT": "45678",
    "SELENIUM_HOST": "selenium",
    "REDIS_URL": "redis://redis:6379/1"
  },

  // Use 'forwardPorts' to make a list of ports inside the container available locally.
  "forwardPorts": [3000, 6379],

  // Configure tool-specific properties.
  // "customizations": {},

  // Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
  // "remoteUser": "root",

  "mounts": [
    {
      "type": "bind",
      "source": "/Users/prasanthchaduvula/Documents/rails",
      "target": "/Users/prasanthchaduvula/Documents/rails"
    }
  ],

  // Use 'postCreateCommand' to run commands after the container is created.
  "postCreateCommand": "bin/setup"
}

Read about the new dev container support introduced in Rails 7.2 in our previous blog Rails 7.2 Adds Support For Devcontainer.

After

Rails 8 does not include redis by default in generated dev containers.

In Rails 8, newly generated apps will use the Solid Queue and Solid Cache gems by default, which do not depend on Redis.

When generating a dev container for an existing app, Rails will not include redis if either of the solid gems are in use.

In the newly generated dev container files, Redis won’t be present.

Here is the default .devcontainer/compose.yaml

name: "rails8_alpha_app"

services:
  rails-app:
    build:
      context: ..
      dockerfile: .devcontainer/Dockerfile

    volumes:
    - ../..:/workspaces:cached

    # Overrides default command so things don't shut down after the process ends.
    command: sleep infinity

    # Uncomment the next line to use a non-root user for all processes.
    # user: vscode

    # Use "forwardPorts" in **devcontainer.json** to forward an app port locally.
    # (Adding the "ports" property to this file will not forward from a Codespace.)
    depends_on:
    - selenium

  selenium:
    image: selenium/standalone-chromium
    restart: unless-stopped

Here is the default .devcontainer/devcontainer.json

// For format details, see https://aka.ms/devcontainer.json. For config options, see the
// README at: https://github.com/devcontainers/templates/tree/main/src/ruby
{
  "name": "rails8_alpha_app",
  "dockerComposeFile": "compose.yaml",
  "service": "rails-app",
  "workspaceFolder": "/workspaces/${localWorkspaceFolderBasename}",

  // Features to add to the dev container. More info: https://containers.dev/features.
  "features": {
    "ghcr.io/devcontainers/features/github-cli:1": {},
    "ghcr.io/rails/devcontainer/features/activestorage": {},
    "ghcr.io/rails/devcontainer/features/sqlite3": {}
  },

  "containerEnv": {
    "CAPYBARA_SERVER_PORT": "45678",
    "SELENIUM_HOST": "selenium"
  },

  // Use 'forwardPorts' to make a list of ports inside the container available locally.
  "forwardPorts": [3000],

  // Configure tool-specific properties.
  // "customizations": {},

  // Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
  // "remoteUser": "root",


  // Use 'postCreateCommand' to run commands after the container is created.
  "postCreateCommand": "bin/setup --skip-server"
}

Rails include Redis if --skip-solid is used when generating an app that use ActiveJob or ActionCable.

Rails 8 does not include redis by default in the dev container.

Before

After

Rails 7.2 Adds Support For Devcontainer.

The Ultimate Guide to Gemfile and Gemfile.lock

Puma-dev And Using It With Rails Applications.