"""Module that provides a cron-like task scheduler. This task scheduler is designed to be used from inside your own program. You can schedule Python functions to be called at specific intervals or days. It uses the standard 'sched' module for the actual task scheduling, but provides much more: * repeated tasks (at intervals, or on specific days) * error handling (exceptions in tasks don't kill the scheduler) * optional to run scheduler in its own thread or separate process * optional to run a task in its own thread or separate process If the threading module is available, you can use the various Threaded variants of the scheduler and associated tasks. If threading is not available, you could still use the forked variants. If fork is also not available, all processing is done in a single process, sequentially. There are three Scheduler classes: Scheduler ThreadedScheduler ForkedScheduler You usually add new tasks to a scheduler using the add_interval_task or add_daytime_task methods, with the appropriate processmethod argument to select sequential, threaded or forked processing. NOTE: it is impossible to add new tasks to a ForkedScheduler, after the scheduler has been started! For more control you can use one of the following Task classes and use schedule_task or schedule_task_abs: IntervalTask ThreadedIntervalTask ForkedIntervalTask SingleTask ThreadedSingleTask ForkedSingleTask WeekdayTask ThreadedWeekdayTask ForkedWeekdayTask MonthdayTask ThreadedMonthdayTask ForkedMonthdayTask Kronos is the Greek God of Time. Kronos scheduler (c) Irmen de Jong. This version has been extracted from the Turbogears source repository and slightly changed to be completely stand-alone again. Also some fixes have been made to make it work on Python 2.6 (sched module changes). The version in Turbogears is based on the original stand-alone Kronos. This is open-source software, released under the MIT Software License: http://www.opensource.org/licenses/mit-license.php """ __version__="2.0" __all__ = [ "DayTaskRescheduler", "ForkedIntervalTask", "ForkedMonthdayTask", "ForkedScheduler", "ForkedSingleTask", "ForkedTaskMixin", "ForkedWeekdayTask", "IntervalTask", "MonthdayTask", "Scheduler", "SingleTask", "Task", "ThreadedIntervalTask", "ThreadedMonthdayTask", "ThreadedScheduler", "ThreadedSingleTask", "ThreadedTaskMixin", "ThreadedWeekdayTask", "WeekdayTask", "add_interval_task", "add_monthday_task", "add_single_task", "add_weekday_task", "cancel", "method", ] import os import sys import sched import time import traceback import weakref class method: sequential="sequential" forked="forked" threaded="threaded" class Scheduler: """The Scheduler itself.""" def __init__(self): self.running=True self.sched = sched.scheduler(time.time, self.__delayfunc) def __delayfunc(self, delay): # This delay function is basically a time.sleep() that is # divided up, so that we can check the self.running flag while delaying. # there is an additional check in here to ensure that the top item of # the queue hasn't changed if delay<10: time.sleep(delay) else: toptime = self._getqueuetoptime() endtime = time.time() + delay period = 5 stoptime = endtime - period while self.running and stoptime > time.time() and \ self._getqueuetoptime() == toptime: time.sleep(period) if not self.running or self._getqueuetoptime() != toptime: return now = time.time() if endtime > now: time.sleep(endtime - now) def _acquire_lock(self): pass def _release_lock(self): pass def add_interval_task(self, action, taskname, initialdelay, interval, processmethod, args, kw): """Add a new Interval Task to the schedule. A very short initialdelay or one of zero cannot be honored, you will see a slight delay before the task is first executed. This is because the scheduler needs to pick it up in its loop. """ if initialdelay < 0 or interval < 1: raise ValueError("Delay or interval must be >0") # Select the correct IntervalTask class. Not all types may be available! if processmethod == method.sequential: TaskClass = IntervalTask elif processmethod == method.threaded: TaskClass = ThreadedIntervalTask elif processmethod == method.forked: TaskClass = ForkedIntervalTask else: raise ValueError("Invalid processmethod") if not args: args = [] if not kw: kw = {} task = TaskClass(taskname, interval, action, args, kw) self.schedule_task(task, initialdelay) return task def add_single_task(self, action, taskname, initialdelay, processmethod, args, kw): """Add a new task to the scheduler that will only be executed once.""" if initialdelay < 0: raise ValueError("Delay must be >0") # Select the correct SingleTask class. Not all types may be available! if processmethod == method.sequential: TaskClass = SingleTask elif processmethod == method.threaded: TaskClass = ThreadedSingleTask elif processmethod == method.forked: TaskClass = ForkedSingleTask else: raise ValueError("Invalid processmethod") if not args: args = [] if not kw: kw = {} task = TaskClass(taskname, action, args, kw) self.schedule_task(task, initialdelay) return task def add_daytime_task(self, action, taskname, weekdays, monthdays, timeonday, processmethod, args, kw): """Add a new Day Task (Weekday or Monthday) to the schedule.""" if weekdays and monthdays: raise ValueError("You can only specify weekdays or monthdays, " "not both") if not args: args = [] if not kw: kw = {} if weekdays: # Select the correct WeekdayTask class. # Not all types may be available! if processmethod == method.sequential: TaskClass = WeekdayTask elif processmethod == method.threaded: TaskClass = ThreadedWeekdayTask elif processmethod == method.forked: TaskClass = ForkedWeekdayTask else: raise ValueError("Invalid processmethod") task=TaskClass(taskname, weekdays, timeonday, action, args, kw) if monthdays: # Select the correct MonthdayTask class. # Not all types may be available! if processmethod == method.sequential: TaskClass = MonthdayTask elif processmethod == method.threaded: TaskClass = ThreadedMonthdayTask elif processmethod == method.forked: TaskClass = ForkedMonthdayTask else: raise ValueError("Invalid processmethod") task=TaskClass(taskname, monthdays, timeonday, action, args, kw) firsttime=task.get_schedule_time(True) self.schedule_task_abs(task, firsttime) return task def schedule_task(self, task, delay): """Add a new task to the scheduler with the given delay (seconds). Low-level method for internal use. """ if self.running: # lock the sched queue, if needed self._acquire_lock() try: task.event = self.sched.enter(delay, 0, task, (weakref.ref(self),) ) finally: self._release_lock() else: task.event = self.sched.enter(delay, 0, task, (weakref.ref(self),) ) def schedule_task_abs(self, task, abstime): """Add a new task to the scheduler for the given absolute time value. Low-level method for internal use. """ if self.running: # lock the sched queue, if needed self._acquire_lock() try: task.event = self.sched.enterabs(abstime, 0, task, (weakref.ref(self),) ) finally: self._release_lock() else: task.event = self.sched.enterabs(abstime, 0, task, (weakref.ref(self),) ) def start(self): """Start the scheduler.""" self._run() def stop(self): """Remove all pending tasks and stop the Scheduler.""" self.running = False self._clearschedqueue() def cancel(self, task): """Cancel given scheduled task.""" self.sched.cancel(task.event) if sys.version_info>=(2,6): # code for sched module of python 2.6+ def _getqueuetoptime(self): return self.sched._queue[0].time def _clearschedqueue(self): self.sched._queue[:] = [] else: # code for sched module of python 2.5 and older def _getqueuetoptime(self): return self.sched.queue[0][0] def _clearschedqueue(self): self.sched.queue[:] = [] def _run(self): # Low-level run method to do the actual scheduling loop. while self.running: try: self.sched.run() except Exception,x: print >>sys.stderr, "ERROR DURING SCHEDULER EXECUTION",x print >>sys.stderr, "".join( traceback.format_exception(*sys.exc_info())) print >>sys.stderr, "-" * 20 # queue is empty; sleep a short while before checking again if self.running: time.sleep(5) class Task: """Abstract base class of all scheduler tasks""" def __init__(self, name, action, args, kw): """This is an abstract class!""" self.name=name self.action=action self.args=args self.kw=kw def __call__(self, schedulerref): """Execute the task action in the scheduler's thread.""" try: self.execute() except Exception,x: self.handle_exception(x) self.reschedule(schedulerref()) def reschedule(self, scheduler): """This method should be defined in one of the sub classes!""" raise NotImplementedError("You're using the abstract base class 'Task'," " use a concrete class instead") def execute(self): """Execute the actual task.""" self.action(*self.args, **self.kw) def handle_exception(self, exc): """Handle any exception that occured during task execution.""" print >>sys.stderr, "ERROR DURING TASK EXECUTION", exc print >>sys.stderr, "".join(traceback.format_exception(*sys.exc_info())) print >>sys.stderr, "-" * 20 class SingleTask(Task): """A task that only runs once.""" def reschedule(self, scheduler): pass class IntervalTask(Task): """A repeated task that occurs at certain intervals (in seconds).""" def __init__(self, name, interval, action, args=None, kw=None): Task.__init__(self, name, action, args, kw) self.interval = interval def reschedule(self, scheduler): """Reschedule this task according to its interval (in seconds).""" scheduler.schedule_task(self, self.interval) class DayTaskRescheduler: """A mixin class that contains the reschedule logic for the DayTasks.""" def __init__(self, timeonday): self.timeonday = timeonday def get_schedule_time(self, today): """Calculate the time value at which this task is to be scheduled.""" now = list(time.localtime()) if today: # schedule for today. let's see if that is still possible if (now[3], now[4]) >= self.timeonday: # too bad, it will be tomorrow now[2] += 1 else: # tomorrow now[2] += 1 # set new time on day (hour,minute) now[3], now[4] = self.timeonday # seconds now[5] = 0 return time.mktime(now) def reschedule(self, scheduler): """Reschedule this task according to the daytime for the task. The task is scheduled for tomorrow, for the given daytime. """ # (The execute method in the concrete Task classes will check # if the current day is a day on which the task must run). abstime = self.get_schedule_time(False) scheduler.schedule_task_abs(self, abstime) class WeekdayTask(DayTaskRescheduler, Task): """A task that is called at specific days in a week (1-7), at a fixed time on the day. """ def __init__(self, name, weekdays, timeonday, action, args=None, kw=None): if type(timeonday) not in (list, tuple) or len(timeonday) != 2: raise TypeError("timeonday must be a 2-tuple (hour,minute)") if type(weekdays) not in (list, tuple): raise TypeError("weekdays must be a sequence of weekday numbers " "1-7 (1 is Monday)") DayTaskRescheduler.__init__(self, timeonday) Task.__init__(self, name, action, args, kw) self.days = weekdays def execute(self): # This is called every day, at the correct time. We only need to # check if we should run this task today (this day of the week). weekday = time.localtime().tm_wday + 1 if weekday in self.days: self.action(*self.args, **self.kw) class MonthdayTask(DayTaskRescheduler, Task): """A task that is called at specific days in a month (1-31), at a fixed time on the day. """ def __init__(self, name, monthdays, timeonday, action, args=None, kw=None): if type(timeonday) not in (list, tuple) or len(timeonday) != 2: raise TypeError("timeonday must be a 2-tuple (hour,minute)") if type(monthdays) not in (list, tuple): raise TypeError("monthdays must be a sequence of monthdays numbers " "1-31") DayTaskRescheduler.__init__(self, timeonday) Task.__init__(self, name, action, args, kw) self.days = monthdays def execute(self): # This is called every day, at the correct time. We only need to # check if we should run this task today (this day of the month). if time.localtime().tm_mday in self.days: self.action(*self.args, **self.kw) try: import threading class ThreadedScheduler(Scheduler): """A Scheduler that runs in its own thread.""" def __init__(self): Scheduler.__init__(self) # we require a lock around the task queue self._lock = threading.Lock() def start(self): """Splice off a thread in which the scheduler will run.""" self.thread = threading.Thread(target=self._run) self.thread.setDaemon(True) self.thread.start() def stop(self): """Stop the scheduler and wait for the thread to finish.""" Scheduler.stop(self) try: self.thread.join() except AttributeError: pass def _acquire_lock(self): """Lock the thread's task queue.""" self._lock.acquire() def _release_lock(self): """Release the lock on th ethread's task queue.""" self._lock.release() class ThreadedTaskMixin: """A mixin class to make a Task execute in a separate thread.""" def __call__(self, schedulerref): """Execute the task action in its own thread.""" threading.Thread(target=self.threadedcall).start() self.reschedule(schedulerref()) def threadedcall(self): # This method is run within its own thread, so we have to # do the execute() call and exception handling here. try: self.execute() except Exception,x: self.handle_exception(x) class ThreadedIntervalTask(ThreadedTaskMixin, IntervalTask): """Interval Task that executes in its own thread.""" pass class ThreadedSingleTask(ThreadedTaskMixin, SingleTask): """Single Task that executes in its own thread.""" pass class ThreadedWeekdayTask(ThreadedTaskMixin, WeekdayTask): """Weekday Task that executes in its own thread.""" pass class ThreadedMonthdayTask(ThreadedTaskMixin, MonthdayTask): """Monthday Task that executes in its own thread.""" pass except ImportError: # threading is not available pass if hasattr(os, "fork"): import signal class ForkedScheduler(Scheduler): """A Scheduler that runs in its own forked process.""" def __del__(self): if hasattr(self, "childpid"): os.kill(self.childpid, signal.SIGKILL) def start(self): """Fork off a new process in which the scheduler will run.""" pid = os.fork() if pid == 0: # we are the child signal.signal(signal.SIGUSR1, self.signalhandler) self._run() os._exit(0) else: # we are the parent self.childpid = pid # can no longer insert in the scheduler queue del self.sched def stop(self): """Stop the scheduler and wait for the process to finish.""" os.kill(self.childpid, signal.SIGUSR1) os.waitpid(self.childpid, 0) def signalhandler(self, sig, stack): Scheduler.stop(self) class ForkedTaskMixin: """A mixin class to make a Task execute in a separate process.""" def __call__(self, schedulerref): """Execute the task action in its own process.""" pid = os.fork() if pid == 0: # we are the child try: self.execute() except Exception,x: self.handle_exception(x) os._exit(0) else: # we are the parent self.reschedule(schedulerref()) class ForkedIntervalTask(ForkedTaskMixin, IntervalTask): """Interval Task that executes in its own process.""" pass class ForkedSingleTask(ForkedTaskMixin, SingleTask): """Single Task that executes in its own process.""" pass class ForkedWeekdayTask(ForkedTaskMixin, WeekdayTask): """Weekday Task that executes in its own process.""" pass class ForkedMonthdayTask(ForkedTaskMixin, MonthdayTask): """Monthday Task that executes in its own process.""" pass if __name__=="__main__": def testaction(arg): print ">>>TASK",arg,"sleeping 3 seconds" time.sleep(3) print "<<