Added django_cron

django_cron/base.py

@@ -0,0 +1,127 @@
+"""
+Copyright (c) 2007-2008, Dj Gilcrease
+All rights reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+"""
+import cPickle
+from threading import Timer
+from datetime import datetime
+
+from django.dispatch import dispatcher
+from django.conf import settings
+
+from signals import cron_done
+import models
+
+# how often to check if jobs are ready to be run (in seconds)
+# in reality if you have a multithreaded server, it may get checked
+# more often that this number suggests, so keep an eye on it...
+# default value: 300 seconds == 5 min
+polling_frequency = getattr(settings, "CRON_POLLING_FREQUENCY", 300)
+
+class Job(object):
+	# 86400 seconds == 24 hours
+	run_every = 86400
+
+	def run(self, *args, **kwargs):  
+		self.job()
+		cron_done.send(sender=self, *args, **kwargs)
+		
+	def job(self):
+		"""
+		Should be overridden (this way is cleaner, but the old way - overriding run() - will still work)
+		"""
+		pass
+
+class CronScheduler(object):
+	def register(self, job_class, *args, **kwargs):
+		"""
+		Register the given Job with the scheduler class
+		"""
+		
+		job_instance = job_class()
+		
+		if not isinstance(job_instance, Job):
+			raise TypeError("You can only register a Job not a %r" % job_class)
+
+		job, created = models.Job.objects.get_or_create(name=str(job_instance.__class__))
+		if created:
+			job.instance = cPickle.dumps(job_instance)
+		job.args = cPickle.dumps(args)
+		job.kwargs = cPickle.dumps(kwargs)
+		job.run_frequency = job_instance.run_every
+		job.save()
+
+	def execute(self):
+		"""
+		Queue all Jobs for execution
+		"""
+		status, created = models.Cron.objects.get_or_create(pk=1)
+		
+		# This is important for 2 reasons:
+		#     1. It keeps us for running more than one instance of the
+		#        same job at a time
+		#     2. It reduces the number of polling threads because they
+		#        get killed off if they happen to check while another
+		#        one is already executing a job (only occurs with
+		#		 multi-threaded servers)
+		if status.executing:
+			return
+
+		status.executing = True
+		try:
+			status.save()
+		except:
+			# this will fail if you're debugging, so we want it
+			# to fail silently and start the timer again so we 
+			# can pick up where we left off once debugging is done
+			Timer(polling_frequency, self.execute).start()
+			return
+			
+		jobs = models.Job.objects.all()
+		for job in jobs:
+			if job.queued:
+				time_delta = datetime.now() - job.last_run
+				if (time_delta.seconds + 86400*time_delta.days) > job.run_frequency:
+					inst = cPickle.loads(str(job.instance))
+					args = cPickle.loads(str(job.args))
+					kwargs = cPickle.loads(str(job.kwargs))
+					
+					try:
+						inst.run(*args, **kwargs)
+						job.last_run = datetime.now()
+						job.save()
+						
+					except Exception:
+						# if the job throws an error, just remove it from
+						# the queue. That way we can find/fix the error and
+						# requeue the job manually
+						job.queued = False
+						job.save()
+
+		status.executing = False
+		status.save()
+		
+		# Set up for this function to run again
+		Timer(polling_frequency, self.execute).start()
+
+
+cronScheduler = CronScheduler()
+