Turbo::Train

Real-time page updates for your Rails app over SSE with Mercure or Fanout Cloud and Hotwire Turbo.

• Uses SSE. No more websockets, client libraries, JS code and handling reconnects. Just an HTTP connection. Let the browser do the work.
• Seamless Hotwire integration. Use it exactly like ActionCable. Drop-in replacement for broadcast_action_to and usual helpers.
• Simple. Get running in minutes, scale easily in production 🚀

Before your proceed

Using this gem requires some knowledge of ActionCable and broadcasting turbo streams. Turbo::Train is designed to mimic those, so it is highly recommended to first try the original to understand the concept.

You can start here and proceed with the Turbo Handbook. One of its chapters will be covering Turbo Streams. Specifically this section would be the main prerequisite to understanding what this gem is about: it covers Broadcastable and the overall idea of working with Mercure or Fanout Cloud.

Prerequisites

1. Rails 7+
2. Mercure server (setup instructions below)

This should also work for Rails 6, but you will also need to install turbo-rails manually before this gem.

Installation

Step 1. Turbo::Train

Instructions for Rails 7+

1. Add the turbo-train gem to your Gemfile: gem 'turbo-train'
2. Run bundle install
3. Run rails turbo_train:install

Instructions for Rails 6

1. Install turbo-rails
2. Repeat steps for Rails 7 above

Step 2. Server

Mercure

Mercure is installed as a plugin to Caddy server. For mac users everything is pretty easy:

brew install caddy

caddy add-package github.com/dunglas/mercure/caddy

Now you are ready to run 🚀

caddy run

Fanout Cloud

We only support the cloud version today. To use Fanout you must purchase a paid account with a contract for Fastly's services.

Fanout self-hosted (Pushpin)

Coming soon.

Usage

If you are familiar with broadcasting from ActionCable, usage would be extremely familiar:

<%# app/views/chat_messages/index.html.erb %>
<%= turbo_train_from "chat_messages" %>

<div id="append_new_messages_here"></div>

And then you can send portions of HTML from your Rails backend to deliver live to all currently open browsers:

Turbo::Train.broadcast_action_to(
  'chat_messages',
  action: :append,
  target:'append_new_messages_here',
  html: '<span>Test!</span>'
)

or in real world you'd probably have something like

# app/models/chat_message.rb
after_create_commit do
  Turbo::Train.broadcast_action_to(
    'chat_messages',
    action: :append,
    target: 'append_new_messages_here',
    partial: 'somepath/message'
  )
end

You have the same options as original Rails Turbo helpers: rendering partials, pure html, same actions.

Configuration

To specify different Mercure or Fanout server settings, please adjust the generated config/initializers/turbo_train.rb file:

Turbo::Train.configure do |config|
  config.skip_ssl_verification = true # Development only; don't do this in production
  config.default_server = :fanout # Default value is :mercure

  config.server :mercure do |mercure|
    mercure.mercure_domain = ...
    mercure.publisher_key = ...
    mercure.subscriber_key = ...
  end

  config.server :fanout do |fanout|
    fanout.service_url = ...
    fanout.service_id = ...
    fanout.fastly_key = ...
  end
end

Mercure

• Your SSE will connect to https://#{configuration.mercure_domain}/.well-known.
• The publisher/subscriber key correspond to the configuration or your Mercure server.

By default, these are set to localhost/test/testing to match the configuration of the local development server from the installation instructions above.

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License

The gem is available as open source under the terms of the MIT License.