gistfile1.py

    def setup_trustmap_computations(self, params):
        
        service = 'trustmap.compute'
        userkey = params['userkey'] # db.Key
        context = params['context'] # str
        timestamp = params['timestamp'] # db.DateTimeProperty
        
        # due to appengine's whims, or if we exceed the request deadline
        # this method may be called multiple times with the same params
        # if so, we resume where we last left off
        # otherwise, we start by querying to get a list of users who we need
        # to create helper tasks for
        
        dukey = u'%s-%s-%s' % (str(userkey), context, timestamp)
        du = DirtyUsers.get_or_insert(keyname=dukey)
        if not du.is_saved():
            users = get_affected_users(userkey, context)
            du.users = users
        
        def save(helper_tasks, du):
            if du.users:
                db.put(helper_tasks + [du])
            else:
                if helper_tasks:
                    db.put(helper_tasks)
                if du.is_saved():
                    db.delete(du)
            helper_tasks[:] = []
        
        
        # we iterate through the list of users, creating helper tasks along the way
        
        try:
            helper_tasks = []
            for item in users:
                hash_ = trustmap_compute_hasher(item, context)
                ht = HelperTask.get_or_insert(hash_, service=service, task=task, parent=du)
                helper_tasks.append(ht)
                processed_users.append(item)
                try:
                    du.users.remove(item)
                except ValueError:
                    pass
                # when we get a signifiant batch, we store it along the way
                if len(helper_tasks) > 19:
                    db.run_in_transaction(save, helper_tasks, du)
        except DeadlineExceededError, e:
            logging.info(e)
        
        # then when either done, or killed due to DeadlineExceededError we
        # either save where we're up to or clean up
        
        finally:
            db.run_in_transaction(save, helper_tasks, du)