def start(self):
        """ Begins the job by kicking off all tasks with no dependencies. """

        logger.info('Job {0} starting job run'.format(self.name))
        if not self.state.allow_start:
            raise DagobahError('job cannot be started in its current state; ' +
                               'it is probably already running')

        self.initialize_snapshot()

        # don't increment if the job was run manually
        if self.cron_iter and datetime.utcnow() > self.next_run:
            self.next_run = self.cron_iter.get_next(datetime)

        self.run_log = {'job_id': self.job_id,
                        'name': self.name,
                        'parent_id': self.parent.dagobah_id,
                        'log_id': self.backend.get_new_log_id(),
                        'start_time': datetime.utcnow(),
                        'tasks': {}}
        self._set_status('running')

        logger.debug('Job {0} resetting all tasks prior to start'.format(self.name))
        for task in self.tasks.itervalues():
            task.reset()

        logger.debug('Job {0} seeding run logs'.format(self.name))
        for task_name in self.ind_nodes(self.snapshot):
            self._put_task_in_run_log(task_name)
            self.tasks[task_name].start()

        self._commit_run_log()
Begins the job by kicking off all tasks with no dependencies.