instance method pubsub_adapter

# File actioncable/lib/action_cable/configuration.rb, line 42
    def pubsub_adapter
      # Provided explicitly in the configuration
      return @pubsub_adapter.constantize if @pubsub_adapter

      adapter = (cable.fetch("adapter") { "redis" })

      # Require the adapter itself and give useful feedback about
      #     1. Missing adapter gems and
      #     2. Adapter gems' missing dependencies.
      path_to_adapter = "action_cable/subscription_adapter/#{adapter}"
      begin
        require path_to_adapter
      rescue LoadError => e
        # We couldn't require the adapter itself. Raise an exception that points out
        # config typos and missing gems.
        if e.path == path_to_adapter
          # We can assume that a non-builtin adapter was specified, so it's either
          # misspelled or missing from Gemfile.
          raise e.class, "Could not load the '#{adapter}' Action Cable pubsub adapter. Ensure that the adapter is spelled correctly in config/cable.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace

        # Bubbled up from the adapter require. Prefix the exception message with some
        # guidance about how to address it and reraise.
        else
          raise e.class, "Error loading the '#{adapter}' Action Cable pubsub adapter. Missing a gem it depends on? #{e.message}", e.backtrace
        end
      end

      adapter = adapter.camelize
      adapter = "PostgreSQL" if adapter == "Postgresql"
      "ActionCable::SubscriptionAdapter::#{adapter}".constantize
    end