[TransWarp] PROPOSAL: refactoring of peak.running.daemons

[Ulrich Eck]

[snip proposal]

i've worked with Jim Fulton on a Task Schedule for Zope3
(meant to be a low-resolution Schedule e.g. once per sec/min/..)

we designed a similar system as you're implementing and i wanted
to give you a chance to look at the interfaces we defined:

In our concept there play to parts:

Schedule and Tasks

A Schedule manages tasks (Stored in a OO-BTree with
datetime as Key -> [Tasks,] as Value)

calling the process method below with a datetime causes all
Tasks that need to be processed get __call__(ed).
If a Task has an internal error, it returns another Task-object
otherwise None. When the processing is finished, the schedule
method on a Task is called to give the Task a chanche to reschedule
itself.



Interface (pre namegeddon):

class ISchedule(Interface):
    """A Task Queue with Scheduling Policy
    """

    def schedule(task):
        """add a task to the Queue
        """

    def unschedule(task):
        """remove a task from the Queue
        """


class IScheduleControl(Interface):
    """A Task Queue Control Interface
    """

    def process(time):
        """Process due tasks
        """

    def getTaskTimes():
        """Return all datetimes for scheduled Tasks
        """

class ITask(Interface):

    time = Datetime(description=u"The time at which the 
                                  task should execute",
                    readonly=1,
                    required=1)

    principalId = Line(description=u"The principalId that 
                                     the task should be executed as.",
                     readonly=1,
                     required=1)

    description = Text(description=u"The description of the 
                                     task for task ")


    def __call__():
        """Execute the task

        Exceptions raised by execute will be logged.

        If execution is sucessful, return None.

        A task may be returned to retry work after an error.
        """

    def schedule():
        """Schedule a new task

        If the execution of the task is sucessful 
        (execute returns None),

        then schedule is called to optionally (re)schedule a task.

        None may be returned if no task needs to be scheduled.

        This method is used to implement repeating tasks.
        """


i don't know if this scheme is suitable for what you want as well.


cheers

Ulrich Eck