--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/soc/cron/job.py	Sat Apr 18 14:04:11 2009 +0000
@@ -0,0 +1,143 @@
+#!/usr/bin/python2.5
+#
+# Copyright 2009 the Melange authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Cron jobs.
+"""
+
+__authors__ = [
+    '"Sverre Rabbelier" <sverre@rabbelier.nl>',
+  ]
+
+
+import logging
+
+from google.appengine.ext import db
+from google.appengine.runtime import DeadlineExceededError
+
+from soc.models.job import Job
+
+
+class Handler(object):
+  """A handler that dispatches a cron job.
+
+  The tasks that are mapped into tasks will be called when a worker
+  has claimed the job. However, there is no guarantee as to how long
+  the task will be allowed to run. If an Exception is raised the task
+  is automatically rescheduled for execution.
+  """
+
+  def __init__(self):
+    """Constructs a new Handler with all known jobs set.
+    """
+
+    self.tasks = {}
+    self.tasks['sendAcceptanceEmail'] = logging.info
+
+  def claimJob(self, job_key):
+    """A transaction to claim a job.
+    """
+
+    job = Job.get_by_id(job_key)
+
+    if job.status != 'waiting':
+      raise db.Rollback()
+
+    job.status = 'started'
+
+    if job.put():
+      return job
+    else:
+      return None
+
+  def freeJob(self, job_key):
+    """A transaction to free a job.
+    """
+
+    job = Job.get_by_id(job_key)
+
+    job.status = 'waiting'
+
+    return job.put()
+
+  def failJob(self, job_key):
+    """A transaction to fail a job.
+    """
+
+    job = Job.get_by_id(job_key)
+
+    job.errors += 1
+
+    if job.errors > 5:
+      job.status = 'aborted'
+    else:
+      job.status = 'waiting'
+
+    job_id = job.key().id()
+    logging.warning("job %d now failed %d time(s)" % (job_id, job.errors))
+
+    return job.put()
+
+  def finishJob(self, job_key):
+    """A transaction to finish a job.
+    """
+
+    job = Job.get_by_id(job_key)
+    job.status = 'finished'
+
+    return job.put()
+
+  def abortJob(self, job_key):
+    """A transaction to abort a job.
+    """
+
+    job = Job.get_by_id(job_key)
+    job.status = 'aborted'
+
+    return job.put()
+
+  def handle(self, job_key):
+    """Handle one job.
+    """
+
+    try:
+      job = db.run_in_transaction(self.claimJob, job_key)
+
+      if not job:
+        # someone already claimed the job
+        return True
+
+      if job.task_name not in self.tasks:
+        logging.error("Unknown job %s" % job.task_name)
+        db.run_in_transaction(self.abortJob, job_key)
+        return True
+
+      task = self.tasks[job.task_name]
+
+      # excecute the actual job
+      task(job)
+
+      db.run_in_transaction(self.finishJob, job_key)
+      return True
+    except DeadlineExceededError, exception:
+      db.run_in_transaction(self.freeJob, job_key)
+      return False
+    except Exception, exception:
+      logging.exception(exception)
+      db.run_in_transaction(self.failJob, job_key)
+      return True
+
+
+handler = Handler()