"""This is the TaskManager Python package.
It provides a system for running any number of predefined tasks in separate
threads in an organized and controlled manner.
A task in this package is a class derived from the Task class. The task
should have a run method that, when called, performs some task.
The Scheduler class is the organizing object. It manages the addition,
execution, deletion, and well being of a number of tasks. Once you have
created your task class, you call the Scheduler to get it added to the
tasks to be run.
"""
from threading import Thread,Event
from TaskHandler import TaskHandler
from time import time
from exceptions import IOError
try: # for Python < 2.3
True, False
except NameError:
True, False = 1, 0
class Scheduler(Thread):
"""The top level class of the TaskManager system.
The Scheduler is a thread that handles organizing and running tasks.
The Scheduler class should be instantiated to start a TaskManager sessions.
Its start method should be called to start the TaskManager.
Its stop method should be called to end the TaskManager session.
"""
## Init ##
def __init__(self, daemon=True, exceptionHandler=None):
Thread.__init__(self)
self._notifyEvent = Event()
self._nextTime = None
self._scheduled = {}
self._running = {}
self._onDemand = {}
self._isRunning = False
self._exceptionHandler = exceptionHandler
if daemon:
self.setDaemon(True)
## Event Methods ##
def wait(self, seconds=None):
"""Our own version of wait().
When called, it waits for the specified number of seconds, or until
it is notified that it needs to wake up, through the notify event.
"""
try:
self._notifyEvent.wait(seconds)
except IOError:
pass
self._notifyEvent.clear()
## Attributes ##
def runningTasks(self):
return self._running
def running(self, name, default=None):
"""Return running task with given name.
Returns a task with the given name from the "running" list,
if it is present there.
"""
return self._running.get(name, default)
def hasRunning(self, name):
"""Check to see if a task with the given name is currently running."""
return self._running.has_key(name)
def setRunning(self, handle):
"""Add a task to the running dictionary.
Used internally only.
"""
self._running[handle.name()] = handle
def delRunning(self, name):
"""Delete a task from the running list.
Used Internally.
"""
try:
handle = self._running[name]
del self._running[name]
return handle
except Exception:
return None
def scheduledTasks(self):
return self._scheduled
def scheduled(self, name, default=None):
"""Return a task from the scheduled list."""
return self._scheduled.get(name, default)
def hasScheduled(self, name):
"""Checks whether task with given name is in the scheduled list."""
return self._scheduled.has_key(name)
def setScheduled(self, handle):
"""Add the given task to the scheduled list."""
self._scheduled[handle.name()] = handle
def delScheduled(self, name):
"""Delete a task with the given name from the scheduled list."""
try:
handle = self._scheduled[name]
del self._scheduled[name]
return handle
except Exception:
return None
def onDemandTasks(self):
return self._onDemand
def onDemand(self, name, default=None):
"""Return a task from the onDemand list."""
return self._onDemand.get(name, default)
def hasOnDemand(self, name):
"""Checks whether task with given name is in the onDemand list."""
return self._onDemand.has_key(name)
def setOnDemand(self, handle):
"""Add the given task to the onDemand list."""
self._onDemand[handle.name()] = handle
def delOnDemand(self, name):
"""Delete a task with the given name from the onDemand list."""
try:
handle = self._onDemand[name]
del self._onDemand[name]
return handle
except Exception:
return None
def nextTime(self):
return self._nextTime
def setNextTime(self, time):
self._nextTime = time
def isRunning(self):
return self._isRunning
## Adding Tasks ##
def addTimedAction(self, time, task, name):
"""Add a task to be run once, at a specific time."""
handle = self.unregisterTask(name)
if handle:
handle.reset(time, 0, task, True)
else:
handle = TaskHandler(self, time, 0, task, name)
self.scheduleTask(handle)
def addActionOnDemand(self, task, name):
"""Add a task to be run only on demand.
Adds a task to the scheduler that will not be scheduled
until specifically requested.
"""
handle = self.unregisterTask(name)
if handle:
handle.reset(time(), 0, task, True)
else:
handle = TaskHandler(self, time(), 0, task, name)
self.setOnDemand(handle)
def addDailyAction(self, hour, minute, task, name):
"""Add an action to be run every day at a specific time.
If a task with the given name is already registered with the
scheduler, that task will be removed from the scheduling queue
and registered anew as a periodic task.
Can we make this addCalendarAction? What if we want to run
something once a week? We probably don't need that for Webware,
but this is a more generally useful module. This could be a
difficult function, though. Particularly without mxDateTime.
"""
import time
current = time.localtime(time.time())
currHour = current[3]
currMin = current[4]
if hour > currHour:
hourDifference = hour - currHour
if minute > currMin:
minuteDifference = minute - currMin
elif minute < currMin:
minuteDifference = 60 - currMin + minute
hourDifference -= 1
else:
minuteDifference = 0
elif hour < currHour:
hourDifference = 24 - currHour + hour
if minute > currMin:
minuteDifference = minute - currMin
elif minute < currMin:
minuteDifference = 60 - currMin + minute
hourDifference -= 1
else:
minuteDifference = 0
else:
if minute > currMin:
hourDifference = 0
minuteDifference = minute - currMin
elif minute < currMin:
minuteDifference = 60 - currMin + minute
hourDifference = 23
else:
hourDifference = 0
minuteDifference = 0
delay = (minuteDifference + (hourDifference * 60)) * 60
self.addPeriodicAction(time.time()+delay, 24*60*60, task, name)
def addPeriodicAction(self, start, period, task, name):
"""Add a task to be run periodically.
Adds an action to be run at a specific initial time,
and every period thereafter.
The scheduler will not reschedule a task until the last
scheduled instance of the task has completed.
If a task with the given name is already registered with
the scheduler, that task will be removed from the scheduling
queue and registered anew as a periodic task.
"""
handle = self.unregisterTask(name)
if handle:
handle.reset(start, period, task, True)
else:
handle = TaskHandler(self, start, period, task, name)
self.scheduleTask(handle)
## Task methods ##
def unregisterTask(self, name):
"""Unregisters the named task.
After that it can be rescheduled with different parameters,
or simply removed.
"""
handle = (self.delRunning(name)
or self.delScheduled(name) or self.delOnDemand(name))
if handle:
handle.unregister()
return handle
def runTaskNow(self, name):
"""Allow a registered task to be immediately executed.
Returns True if the task is either currently running or was started,
or False if the task could not be found in the list of currently
registered tasks.
"""
if self.hasRunning(name):
return True
handle = self.scheduled(name)
if not handle:
handle = self.onDemand(name)
if not handle:
return False
self.runTask(handle)
return True
def demandTask(self, name):
"""Demand execution of a task.
Allow the server to request that a task listed as being registered
on-demand be run as soon as possible.
If the task is currently running, it will be flagged to run again
as soon as the current run completes.
Returns False if the task name could not be found on the on-demand
or currently running lists.
"""
if self.hasRunning(name) or self.hasOnDemand(name):
handle = self.running(name)
if handle:
handle.runOnCompletion()
return True
handle = self.onDemand(name)
if not handle:
return False
self.runTask(handle)
return True
else:
return False
def stopTask(self, name):
"""Put an immediate halt to a running background task.
Returns True if the task was either not running, or was
running and was told to stop.
"""
handle = self.running(name)
if not handle:
return False
handle.stop()
return True
def stopAllTasks(self):
"""Terminate all running tasks."""
for i in self._running.keys():
self.stopTask(i)
def disableTask(self, name):
"""Specify that a task be suspended.
Suspended tasks will not be scheduled until later enabled.
If the task is currently running, it will not be interfered
with, but the task will not be scheduled for execution in
future until re-enabled.
Returns True if the task was found and disabled.
"""
handle = self.running(name)
if not handle:
handle = self.scheduled(name)
if not handle:
return False
handle.disable()
return True
def enableTask(self, name):
"""Enable a task again.
This method is provided to specify that a task be re-enabled
after a suspension. A re-enabled task will be scheduled for
execution according to its original schedule, with any runtimes
that would have been issued during the time the task was suspended
simply skipped.
Returns True if the task was found and enabled.
"""
handle = self.running(name)
if not handle:
handle = self.scheduled(name)
if not handle:
return False
handle.enable()
return True
def runTask(self, handle):
"""Run a task.
Used by the Scheduler thread's main loop to put a task in
the scheduled hash onto the run hash.
"""
name = handle.name()
if self.delScheduled(name) or self.delOnDemand(name):
self.setRunning(handle)
handle.runTask()
def scheduleTask(self, handle):
"""Schedule a task.
This method takes a task that needs to be scheduled and adds it
to the scheduler. All scheduling additions or changes are handled
by this method. This is the only Scheduler method that can notify
the run() method that it may need to wake up early to handle a
newly registered task.
"""
self.setScheduled(handle)
if not self.nextTime() or handle.startTime() < self.nextTime():
self.setNextTime(handle.startTime())
self.notify()
## Misc Methods ##
def notifyCompletion(self, handle):
"""Notify completion of a task.
Used by instances of TaskHandler to let the Scheduler thread know
when their tasks have run to completion. This method is responsible
for rescheduling the task if it is a periodic task.
"""
name = handle.name()
if self.hasRunning(name):
self.delRunning(name)
if handle.startTime() and handle.startTime() > time():
self.scheduleTask(handle)
else:
if handle.reschedule():
self.scheduleTask(handle)
elif handle.isOnDemand():
self.setOnDemand(handle)
if handle.runAgain():
self.runTask(handle)
def notifyFailure(self, handle):
"""Notify failure of a task.
Used by instances of TaskHandler to let the Scheduler thread know
if an exception has occurred within the task thread.
"""
self.notifyCompletion(handle)
if self._exceptionHandler is not None:
self._exceptionHandler()
def notify(self):
self._notifyEvent.set()
def start(self):
"""Start the scheduler's activity."""
self._isRunning = True
Thread.start(self)
def stop(self):
"""Terminate the scheduler and its associated tasks."""
self._isRunning = False
self.notify()
self.stopAllTasks()
# jdh: wait until the scheduler thread exits; otherwise
# it's possible for the interpreter to exit before this thread
# has a chance to shut down completely, which causes a traceback
# cz: but use a timeout of 3 seconds, this should suffice
self.join(3)
## Main Method ##
def run(self):
"""The main method of the scheduler running as a background thread.
This method is responsible for carrying out the scheduling work of
this class on a background thread. The basic logic is to wait until
the next action is due to run, move the task from our scheduled
list to our running list, and run it. Other synchronized methods
such as runTask(), scheduleTask(), and notifyCompletion(), may
be called while this method is waiting for something to happen.
These methods modify the data structures that run() uses to
determine its scheduling needs.
"""
while self._isRunning:
if self.nextTime():
nextTime = self.nextTime()
currentTime = time()
if currentTime < nextTime:
sleepTime = nextTime - currentTime
self.wait(sleepTime)
if not self._isRunning:
return
currentTime = time()
if currentTime >= nextTime:
toRun = []
nextRun = None
for handle in self._scheduled.values():
startTime = handle.startTime()
if startTime <= currentTime:
toRun.append(handle)
else:
if not nextRun:
nextRun = startTime
elif startTime < nextRun:
nextRun = startTime
self.setNextTime(nextRun)
for handle in toRun:
self.runTask(handle)
else:
self.wait()
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