Class: Volt::Dispatcher

Inherits:
Object show all
Defined in:
lib/volt/tasks/dispatcher.rb

Overview

The task dispatcher is responsible for taking incoming messages from the socket channel and dispatching them to the proper handler.

Instance Method Summary collapse

Instance Method Details

#dispatch(channel, message) ⇒ Object

Dispatch takes an incoming Task from the client and runs it on the server, returning the result to the client. Tasks returning a promise will wait to return.



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# File 'lib/volt/tasks/dispatcher.rb', line 9

def dispatch(channel, message)
  callback_id, class_name, method_name, meta_data, *args = message
  method_name = method_name.to_sym

  # Get the class
  klass = Object.send(:const_get, class_name)

  promise = Promise.new

  # Check that we are calling on a TaskHandler class and a method provide at
  # TaskHandler or above in the ancestor chain.
  if safe_method?(klass, method_name)
    promise.resolve(nil)

    # Init and send the method
    promise = promise.then do
      Thread.current['meta'] = meta_data

      result = klass.new(channel, self).send(method_name, *args)

      Thread.current['meta'] = nil

      result
    end

  else
    # Unsafe method
    promise.reject(RuntimeError.new("unsafe method: #{method_name}"))
  end

  if callback_id
    # Run the promise and pass the return value/error back to the client
    promise.then do |result|
      channel.send_message('response', callback_id, result, nil)
    end.fail do |error|
      channel.send_message('response', callback_id, nil, error)
      Volt.logger.error(error)
    end
  end
end

#safe_method?(klass, method_name) ⇒ Boolean

Check if it is safe to use this method

Returns:



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# File 'lib/volt/tasks/dispatcher.rb', line 51

def safe_method?(klass, method_name)
  # Make sure the class being called is a TaskHandler.
  return false unless klass.ancestors.include?(TaskHandler)

  # Make sure the method is defined on the klass we're using and not up the hiearchy.
  #   ^ This check prevents methods like #send, #eval, #instance_eval, #class_eval, etc...
  klass.ancestors.each do |ancestor_klass|
    if ancestor_klass.instance_methods(false).include?(method_name)
      return true
    elsif ancestor_klass == TaskHandler
      # We made it to TaskHandler and didn't find the method, that means it
      # was defined above TaskHandler, so we reject the call.
      return false
    end
  end

  return false
end