class ActionCable::Server::Configuration

in a Rails config initializer.
An instance of this configuration object is available via ActionCable.server.config, which allows you to tweak Action Cable configuration

def initialize 

def initialize
  @log_tags = []
  @connection_class = -> { ActionCable::Connection::Base }
  @worker_pool_size = 4
  @disable_request_forgery_protection = false
  @allow_same_origin_as_host = true
end

def pubsub_adapter

Also makes sure proper dependencies are required.
If the adapter cannot be found, this will default to the Redis adapter.
Returns constant of subscription adapter specified in config/cable.yml. 
def pubsub_adapter
  adapter = (cable.fetch("adapter") { "redis" })
  path_to_adapter = "action_cable/subscription_adapter/#{adapter}"
  begin
    require path_to_adapter
  rescue Gem::LoadError => e
    raise Gem::LoadError, "Specified '#{adapter}' for Action Cable pubsub adapter, but the gem is not loaded. Add `gem '#{e.name}'` to your Gemfile (and ensure its version is at the minimum required by Action Cable)."
  rescue LoadError => e
    raise LoadError, "Could not load '#{path_to_adapter}'. Make sure that the adapter in config/cable.yml is valid. If you use an adapter other than 'postgresql' or 'redis' add the necessary adapter gem to the Gemfile.", e.backtrace
  end
  adapter = adapter.camelize
  adapter = "PostgreSQL" if adapter == "Postgresql"
  "ActionCable::SubscriptionAdapter::#{adapter}".constantize
end