new_contents: # -*- coding: utf-8 -*-
  
  # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  #    Copyright (C) 2012-2013 Yahoo! Inc. All Rights Reserved.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  import logging
  import os
  import random
  import sys
  
  logging.basicConfig(level=logging.ERROR)
  
  top_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
                                         os.pardir,
                                         os.pardir))
  sys.path.insert(0, top_dir)
  
  from taskflow.patterns import graph_flow as gf
  from taskflow.patterns import linear_flow as lf
  
  from taskflow import engines
  from taskflow import task
  
  
  class PrintText(task.Task):
      def __init__(self, print_what):
          super(PrintText, self).__init__(name="Print: %s" % print_what)
          self._text = print_what
  
      def execute(self):
          print("-" * (len(self._text)))
          print(self._text)
          print("-" * (len(self._text)))
  
  
  class AllocateIP(task.Task):
      def execute(self):
          return "192.168.0.%s" % (random.randint(1, 254))
  
  
  class AllocateVolumes(task.Task):
      def execute(self):
          volumes = []
          for i in range(0, random.randint(0, 10)):
              volumes.append("/dev/vda%s" % (i + 1))
          return volumes
  
  
  class CreateVM(task.Task):
      def execute(self, net_ip, volumes):
          print("Making vm %s using ip %s" % (self.name, net_ip))
          if volumes:
              print("With volumes:")
              for v in volumes:
                  print(" - %s" % (v))
  
  
  flow = lf.Flow("root").add(
      PrintText("Starting"),
      gf.Flow('maker').add(
          # First vm creation
          AllocateVolumes("volumes-1", provides='volumes_1'),
          AllocateIP("ip-1", provides='net_ip1'),
          CreateVM("vm-1", rebind=['net_ip1', 'volumes_1']),
          # Second vm creation
          AllocateVolumes("volumes-2", provides='volumes_2'),
          AllocateIP("ip-2", provides='net_ip2'),
          CreateVM("vm-2", rebind=['net_ip2', 'volumes_2'])
      ),
      PrintText("Finished"))
  
  
  # The above vms will be created in parallel, dependencies will be ran in order
  # so that means the ip and volume creation for each vm will run before the
  # final vm creation is done, but both vm creates will run at the same time.
  #
  # Pretty cool!
  engines.run(flow, engine_conf='parallel')
  
subject: Add a secondary booting vm example