How to integrate your application with nodehandler

This tutorial is for users who want to use nodeHandler to launch their applications on the nodes. For example, we assume that you want to launch

   tcpdump -i eth1

on all the nodes in the experiment.

Three steps are needed

Step 1: Create application definition file

This definition tells the nodehandler about your new application that you want to launch. It mainly includes details such as what are the command line options it takes and what are the statistics it returns. Here is a sample application definition for our above application

Think about this as a class definition for your application

• Put this file in your home directory as test_app_tcpdump.rb

#
# Create an application representation from scratch
#
require 'handler/appDefinition'

a = AppDefinition.create('test:app:tcpdump')
a.name = "tcpdump"
a.version(0, 0, 1)
a.shortDescription = "Tcpdump application"
a.description = <<TEXT
TCPDump application
TEXT

# addProperty(name, description, mnemonic, type, isDynamic = false, constraints = nil)

#Here ?i means tcpdump will be launched with -i <interface> option
a.addProperty('interface', 'Interface to run on', ?i, String, false)

# Path of your application on the node/image.
a.path = "/usr/sbin/tcpdump"

if $0 == __FILE__
  require 'stringio'
  require 'rexml/document'
  include REXML

  sio = StringIO.new()
  a.to_xml.write(sio, 2)
  sio.rewind
  puts sio.read

  sio.rewind
  doc = Document.new(sio)
  t = AppDefinition.from_xml(doc.root)

  puts
  puts "-------------------------"
  puts
  t.to_xml.write($stdout, 2)

end

Step 2: Prototype definition

After informing nodeHandler about our new application, we then need to create a prototype using our application definition.

Think about this as an instance of your above class

• Put this file in your home directory as test_proto_tcpdumper.rb

  #
  # Define a prototype
  #
  
  require 'handler/prototype'
  require 'handler/filter'
  require 'handler/appDefinition'
  
  p = Prototype.create("test:proto:tcpdumper")
  p.name = "TCPdump proto"
  p.description = "TCPdump"
  p.defProperty('interface', 'Interface to listen on')
  
  
  tcpd = p.addApplication('tcpd', "test:app:tcpdump")
  tcpd.bindProperty('interface')
  
  
  
  if $0 == __FILE__
    p.to_xml.write($stdout, 2)
    puts
  end
  
  

Step 3: Using this prototype in an actual script

The following example script uses our newly defined application definition.

##################################################
# TCPDump using nodeHandler
##################################################

Experiment.name = "tutorial-tcpdump"
Experiment.project = "orbit:tutorial"

#
# Define nodes used in experiment
#
defNodes('nodes', [[1,1],[1,2]]) {|node|
  node.image = nil  # assume the right image to be on disk

  node.prototype("test:proto:tcpdumper", {
    'interface' => 'eth1' #This is where we assign the interface for this specific instance
   })
  node.net.w0.mode = "master"
}


allNodes.net.w0 { |w|
  w.type = 'b'
  w.essid = "helloworld"
  w.ip = "%192.168.%x.%y"
}

#
# Now, start the application
#
whenAllInstalled() {|node|
 # Launch TCPdump on all nodes

  #startApplications will launch all the applications defined for the group "nodes"
  NodeSet['nodes'].startApplications

 

  wait 180

  Experiment.done
}