Interrupt Problems

[ccf...@gmail.com]

A worker must perform two different tasks in sequence. Work breaks can happen, which I think of as an interrupt. If a break happens, the specific task she is working on should be stopped, the time spent on the task pre-break should be captured, then the specific task resumes using the remaining task duration.

I implemented the following toy example (borrowing heavily from the Machine Shop example in the docs) but unsure how to propagate the break interrupt to the specific task. You'll see that I have commented out code related to the interrupt and provide, hopefully helpful additional comments. Thanks in advance for any help!

Chris

import simpy

class Worker:

  def __init__(self, env):

    self.env = env

    self.work_proc = env.process(self.work())

#   self.break_proc = env.process(self.break_time())

  def work(self):

    while True:

      # two different tasks, w/ different durations

      # 'Task 20' finishes before 'Task 40' starts

      # if you put try/except here, 'Task 20' will

      # resume after interrupt, even though may be

      # on 'Task 40'

      yield self.env.process(self.task(20))

      yield self.env.process(self.task(40))

  def task(self, duration):

    while duration:

      # I put try/except at 'task level'

      # following Machine Shop example

      try:

        start = self.env.now

        yield self.env.timeout(duration)

        print(f'Task {duration} finished at {env.now}')

        duration = 0 # Exits while loop

      except simpy.Interrupt:

        duration -= self.env.now - start

# def break_time(self):

#   yield self.env.timeout(10) # just picked 10, can be anything

    # I would like to interrupt the work process

    # and somehow this gets propagated to the 'in progress' task

#   self.work_proc.interrupt()

env = simpy.Environment()

w = Worker(env)

env.run(until=100)

Task 20 finished at 20

Task 40 finished at 60

Task 20 finished at 80

[Michael Gibbs]

Try this

When a task starts, I save a reference to the process.  This will be the "in process" task.

When my break_time process timeout expires, I simply interrupt the last saved task

A more robust version would check that the task being interrupted is active.

import simpy

class Worker:

  def __init__(self, env):

    self.env = env

    env.process(self.work())

    self.runningTask = None # the in process task

    env.process(self.break_time())

  def work(self):

    while True:

      # two different tasks, w/ different durations

      # 'Task 20' finishes before 'Task 40' starts

      # if you put try/except here, 'Task 20' will

      # resume after interrupt, even though may be

      # on 'Task 40'

      # remember what task in in process

      self.runningTask = self.env.process(self.task(20))

      yield self.runningTask

      self.runningTask = self.env.process(self.task(40))

      yield self.runningTask

  def task(self, duration):

    while duration:

      # I put try/except at 'task level'

      # following Machine Shop example

      try:

        start = self.env.now

        yield self.env.timeout(duration)

        print(f'Task {duration} finished at {env.now}')

        duration = 0 # Exits while loop

      except simpy.Interrupt:

        duration -= self.env.now - start

        print(f'break at {env.now}, has remaining duration of {duration}')

  def break_time(self):

    yield self.env.timeout(30) # just picked 30, can be anything

    #I would like to interrupt the work process

    #and somehow this gets propagated to the 'in progress' task

    # saved the inprocess task, may want to test if process is still live

    self.runningTask.interrupt()

env = simpy.Environment()

w = Worker(env)

env.run(until=100)

[ccf...@gmail.com]

Hi Michael,

Thanks for working through the example in your post. Much appreciated.

Chris