Source code for distlock2.imp_0.checker

"""
Module **distlock2.imp_0.checker** has class Checker, a skeleton checker
for a distlock2 implementation, to be fleshed out by you.
"""

class Checker():
  """
  Maintain global state of a distributed system of two distlock2.imp_0 nodes.
  Receive updates from the nodes and check that the updated global state
  satisfies desired global assertions.
  Instantiated by distlock2.servicetester when testing the distributed system.
  """

  def __init__(self, tester, argv):
    """Example global state:
    - tester: the tester that started this instance;
      allows access to tester.service variables.
    - status[j]: current value of node j's status variable;
      'T' (thinking), 'H' (hungry), or 'E' (eating)
    """
    self.tester = tester
    self.status = ['T', 'T']


  def handle_event(self, event):
    """
    RPC-called by a node to convey event e. Update global state according
    to e and check whether it still statisfies desired assertions.

    - Example event: (j, new_value_of_status[j]).
    - Example assertion: Inv(status[0] == 'E' and status[1] == 'E')
    """
    # print("handle_event called:", event, flush=True)
    j, st = event
    self.status[j] = st
    # check assertion
    if self.status[0] == 'E' and self.status[1] == 'E':
      print("distlock2.imp_0.node", j, "event invalid", flush=True)
    else:
      print("distlock2.imp_0.node", j, "event valid", flush=True)

###### end class Checker ######################