For every WebSocket connection the Action Cable server accepts, a Connection object will be instantiated. This instance becomes the parent of all of the channel subscriptions that are created from there on. Incoming messages are then routed to these channel subscriptions based on an identifier sent by the Action Cable consumer. The Connection itself does not deal with any specific application logic beyond authentication and authorization.

Here's a basic example:

module ApplicationCable
  class Connection < ActionCable::Connection::Base
    identified_by :current_user

    def connect
      self.current_user = find_verified_user
      logger.add_tags current_user.name
    end

    def disconnect
      # Any cleanup work needed when the cable connection is cut.
    end

    private
      def find_verified_user
        User.find_by_identity(cookies.encrypted[:identity_id]) ||
          reject_unauthorized_connection
      end
  end
end

First, we declare that this connection can be identified by its current_user. This allows us to later be able to find all connections established for that current_user (and potentially disconnect them). You can declare as many identification indexes as you like. Declaring an identification means that an attr_accessor is automatically set for that key.

Second, we rely on the fact that the WebSocket connection is established with the cookies from the domain being sent along. This makes it easy to use signed cookies that were set when logging in via a web interface to authorize the WebSocket connection.

Finally, we add a tag to the connection-specific logger with the name of the current user to easily distinguish their messages in the log.

Pretty simple, eh?

Methods

Included Modules

Attributes

[R] env
[R] logger
[R] message_buffer
[R] protocol
[R] server
[R] subscriptions
[R] websocket

TODO Change this to private once we've dropped Ruby 2.2 support. Workaround for Ruby 2.2 “private attribute?” warning.
[R] worker_pool

Class Public methods

new(server, env, coder: ActiveSupport::JSON)

📝 Source code 
# File actioncable/lib/action_cable/connection/base.rb, line 53
      def initialize(server, env, coder: ActiveSupport::JSON)
        @server, @env, @coder = server, env, coder

        @worker_pool = server.worker_pool
        @logger = new_tagged_logger

        @websocket      = ActionCable::Connection::WebSocket.new(env, self, event_loop)
        @subscriptions  = ActionCable::Connection::Subscriptions.new(self)
        @message_buffer = ActionCable::Connection::MessageBuffer.new(self)

        @_internal_subscriptions = nil
        @started_at = Time.now
      end
🔎 See on GitHub

Instance Public methods

beat()

📝 Source code 
# File actioncable/lib/action_cable/connection/base.rb, line 118
      def beat
        transmit type: ActionCable::INTERNAL[:message_types][:ping], message: Time.now.to_i
      end
🔎 See on GitHub

close()

Close the WebSocket connection.

📝 Source code 
# File actioncable/lib/action_cable/connection/base.rb, line 98
      def close
        websocket.close
      end
🔎 See on GitHub

send_async(method, *arguments)

Invoke a method on the connection asynchronously through the pool of thread workers.

📝 Source code 
# File actioncable/lib/action_cable/connection/base.rb, line 103
      def send_async(method, *arguments)
        worker_pool.async_invoke(self, method, *arguments)
      end
🔎 See on GitHub

statistics()

Return a basic hash of statistics for the connection keyed with identifier, started_at, subscriptions, and request_id. This can be returned by a health check against the connection.

📝 Source code 
# File actioncable/lib/action_cable/connection/base.rb, line 109
      def statistics
        {
          identifier: connection_identifier,
          started_at: @started_at,
          subscriptions: subscriptions.identifiers,
          request_id: @env["action_dispatch.request_id"]
        }
      end
🔎 See on GitHub

Instance Private methods

cookies()

The cookies of the request that initiated the WebSocket connection. Useful for performing authorization checks.

📝 Source code 
# File actioncable/lib/action_cable/connection/base.rb, line 155
        def cookies # :doc:
          request.cookie_jar
        end
🔎 See on GitHub

request()

The request that initiated the WebSocket connection is available here. This gives access to the environment, cookies, etc.

📝 Source code 
# File actioncable/lib/action_cable/connection/base.rb, line 147
        def request # :doc:
          @request ||= begin
            environment = Rails.application.env_config.merge(env) if defined?(Rails.application) && Rails.application
            ActionDispatch::Request.new(environment || env)
          end
        end
🔎 See on GitHub