Class: RMB::ListenerMain

Inherits:
Object
  • Object
show all
Defined in:
lib/listener_main.rb

Overview

This is the class that gets instantiated from the listener daemon It contains the worker code of the daemon

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(root, key) ⇒ ListenerMain

initialize Given root (the working directory or RAILS_ROOT) and key (the unique identifier that denotes a particular Listener instance), the initialize method sets up the entire daemon.

  • The daemon name is created from the key

  • A logger object is instantiated for the use of the daemon components

  • A hash of properties is read from a properties file, whose name is also derived from the root and key.

  • An instance of a subclass of Subscriber is created to act as the front end of the daemon, listening on a topic or queue for the arrival of a message

  • An instance of a subclass of Submitter is created to send messages on to a parent rails app, using RESTful techniques to send the message to a rails controller.



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# File 'lib/listener_main.rb', line 17

def initialize(root, key)
  @key = key
  @logger = Logger.new("#{root}/log/#{app_name}.log")
  @logger.info "\nStarting #{File.basename(__FILE__)} --> #{app_name}..."
  @hash = nil
  # load the marshalled hash of properties
  f = File.join("#{root}", "tmp", "properties", "#{app_name}.properties")
  File.open(f) do |props|
    @hash = Marshal.load(props)
  end
  @hash[:logger] = @logger
  # instantiate the two objects that comprise the front-end and the back-end of 
  # this listener daemon
  front = @hash[:subscriber]
  @subscriber = Kernel.eval "#{front[:class_name]}.new"
  @subscriber.properties=@hash
  back = @hash[:submitter]
  @submitter = Kernel.eval "#{back[:class_name]}.new"
  @submitter.properties=@hash
end

Instance Attribute Details

#hash ⇒ Object

Returns the value of attribute hash.



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# File 'lib/listener_main.rb', line 7

def hash
  @hash
end

#logger ⇒ Object

Returns the value of attribute logger.



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# File 'lib/listener_main.rb', line 7

def logger
  @logger
end

#submitter ⇒ Object

Returns the value of attribute submitter.



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# File 'lib/listener_main.rb', line 7

def submitter
  @submitter
end

#subscriber ⇒ Object

Returns the value of attribute subscriber.



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# File 'lib/listener_main.rb', line 7

def subscriber
  @subscriber
end

Instance Method Details

#app_name ⇒ Object 



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# File 'lib/listener_main.rb', line 78

def app_name
  "#{RMB::Properties.daemon_prefix}#{@key}"
end

#run ⇒ Object

run

  • The subscriber is connected to a message broker,

  • the submitter is connected to the rails controller,

  • then an infinite loop is entered

  • subscriber waits to receive a message

  • when a message arrives, it is sent to the rails controller via the submitter

  • …and loop forever



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# File 'lib/listener_main.rb', line 46

def run
  begin
    subscriber.connect
    logger.info "subscriber connected."
  rescue Exception
    logger.fatal "#{__FILE__}:#{__LINE__} Exception #{$!}"
    raise
  end
  begin
    submitter.connect
    logger.info "submitter logged in."
  rescue Exception
    logger.fatal "#{__FILE__}:#{__LINE__} Exception #{$!}"
    raise
  end
  logger.info "Waiting for messages in #{subscriber.url}."
  loop do
    begin
      message = subscriber.receive
    rescue
      logger.fatal "#{__FILE__}:#{__LINE__} Exception #{$!}"
      raise
    end
    begin
      submitter.send(message)
    rescue Exception
      logger.fatal "#{__FILE__}:#{__LINE__} Exception #{$!}"
      raise
    end
  end
end