#! /usr/bin/env python
"""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 addIntervalTask or
addDaytimeTask 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 could use one of the following Task classes
and use scheduleTask or scheduleTaskAbs:
IntervalTask ThreadedIntervalTask ForkedIntervalTask
WeekdayTask ThreadedWeekdayTask ForkedWeekdayTask
MonthdayTask ThreadedMonthdayTask ForkedMonthdayTask
Kronos is the Greek God of Time.
This module requires Python 2.2 or newer.
"""
#
# $Id: kronos.py,v 1.3 2004/10/06 22:44:47 irmen Exp $
#
# (c) Irmen de Jong.
# This is open-source software, released under the MIT Software License:
# http://www.opensource.org/licenses/mit-license.php
#
import os, sys
import sched, time
import traceback
import weakref
class Scheduler:
"""The Scheduler itself."""
# processmethod argument values
PM_SEQUENTIAL = 1
PM_FORKED = 2
PM_THREADED = 3
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.
if delay<10:
time.sleep(delay)
else:
period=5
while self.running and delay>period:
time.sleep(period)
delay-=period
if not self.running:
return
time.sleep(delay)
def _acquireLock(self): pass
def _releaseLock(self): pass
def addIntervalTask(self, action, taskname, initialdelay, interval, processmethod, actionargs):
"""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==self.PM_SEQUENTIAL:
TaskClass=IntervalTask
elif processmethod==self.PM_THREADED:
TaskClass = ThreadedIntervalTask
elif processmethod==self.PM_FORKED:
TaskClass = ForkedIntervalTask
else:
raise ValueError("invalid processmethod")
if not actionargs:
actionargs=[]
task = TaskClass(taskname, interval, action, actionargs)
self.scheduleTask(task, initialdelay)
def addDaytimeTask(self, action, taskname, weekdays, monthdays, timeonday, processmethod, actionargs):
"""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 weekdays:
# Select the correct WeekdayTask class. Not all types may be available!
if processmethod==self.PM_SEQUENTIAL:
TaskClass=WeekdayTask
elif processmethod==self.PM_THREADED:
TaskClass = ThreadedWeekdayTask
elif processmethod==self.PM_FORKED:
TaskClass = ForkedWeekdayTask
else:
raise ValueError("invalid processmethod")
task=TaskClass(taskname, weekdays, timeonday, action, actionargs)
if monthdays:
# Select the correct MonthdayTask class. Not all types may be available!
if processmethod==self.PM_SEQUENTIAL:
TaskClass=MonthdayTask
elif processmethod==self.PM_THREADED:
TaskClass = ThreadedMonthdayTask
elif processmethod==self.PM_FORKED:
TaskClass = ForkedMonthdayTask
else:
raise ValueError("invalid processmethod")
task=TaskClass(taskname, monthdays, timeonday, action, actionargs)
firsttime=task.getScheduleTime(True)
self.scheduleTaskAbs(task, firsttime)
def scheduleTask(self, task, delay):
"""Low-level method to add a new task to the scheduler with the given delay (seconds)."""
if self.running:
self._acquireLock() # lock the sched queue, if needed
try:
self.sched.enter(delay, 0, task, (weakref.ref(self),) )
finally:
self._releaseLock()
def scheduleTaskAbs(self, task, abstime):
"""Low-level method to add a new task to the scheduler for the given absolute time value."""
if self.running:
self._acquireLock() # lock the sched queue, if needed
try:
self.sched.enterabs(abstime, 0, task, (weakref.ref(self),) )
finally:
self._releaseLock()
def start(self):
"""Start the scheduler."""
self._run()
def stop(self):
"""Remove all pending tasks and stop the Scheduler."""
self.running=False
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, actionargs):
"""This is an abstract class!"""
self.name=name
self.action=action
self.actionargs=actionargs
def __call__(self, schedulerref):
"""Execute the task action in the scheduler's thread."""
try:
self.execute()
except Exception,x:
self.handleException(x)
self.reschedule(schedulerref())
def reschedule(self, scheduler):
"""This is an abstract class, this method is 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.actionargs)
def handleException(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 IntervalTask(Task):
"""A repeated task that occurs at certain intervals (in seconds)."""
def __init__(self, name, interval, action, actionargs=None):
Task.__init__(self, name, action, actionargs)
self.interval=interval
def reschedule(self, scheduler):
# reschedule this task according to its interval (in seconds).
scheduler.scheduleTask(self, self.interval)
class DayTaskRescheduler:
"""A mixin class that contains the reschedule logic for the DayTasks."""
def __init__(self, timeonday):
self.timeonday=timeonday
def getScheduleTime(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:
now[2]+=1 # too bad, it will be tomorrow
else:
now[2]+=1 # tomorrow
now[3], now[4] = self.timeonday # set new time on day (hour,minute)
now[5]=0 # seconds
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.getScheduleTime(False)
scheduler.scheduleTaskAbs(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, actionargs=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")
DayTaskRescheduler.__init__(self, timeonday)
Task.__init__(self, name, action, actionargs)
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.actionargs)
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, actionargs=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, actionargs)
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.actionargs)
try:
import threading
class ThreadedScheduler(Scheduler):
"""A Scheduler that runs in its own thread."""
def __init__(self):
Scheduler.__init__(self)
self._lock=threading.Lock() # we require a lock around the task queue
def start(self):
# Start method that splices of 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 method that stops the scheduler and waits for the thread to finish.
Scheduler.stop(self)
self.thread.join()
def _acquireLock(self):
self._lock.acquire() # lock the thread's task queue
def _releaseLock(self):
self._lock.release() # release the thread's task queue
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.handleException(x)
class ThreadedIntervalTask(ThreadedTaskMixin, IntervalTask):
"""Interval 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):
# Start method that forks of 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
del self.sched # can no longer insert in the scheduler queue
def stop(self):
# Stop method that stops the scheduler and waits 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.handleException(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 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
def testaction(arg):
print ">>>TASK",arg,"sleeping 3 seconds"
time.sleep(3)
print "<<<END_TASK",arg
def test():
s=ThreadedScheduler()
s.addIntervalTask( testaction, "test action 1", 0, 4, s.PM_THREADED, ["task 1"] )
s.addDaytimeTask( testaction, "test action daytask", None,[1], (18,22), s.PM_THREADED, ["task 2"])
s.start()
print "Scheduler started, waiting 15 sec...."
time.sleep(15)
print "STOP SCHEDULER"
s.stop()
print "EXITING"
if __name__=="__main__":
test()
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