heat/heat/engine/timestamp.py
Jason Dunsmore af464c9afc Make the first line of every file consistent.
Change-Id: I2e1a809cfca8e88693551d58d33e747f54ee5eb1
2014-03-04 09:03:04 -06:00

47 lines
1.6 KiB
Python

#
# 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.
from heat.common import exception
class Timestamp(object):
'''
A descriptor for writing a timestamp to the database.
'''
def __init__(self, db_fetch, attribute):
'''
Initialise with a function to fetch the database representation of an
object (given a context and ID) and the name of the attribute to
retrieve.
'''
self.db_fetch = db_fetch
self.attribute = attribute
def __get__(self, obj, obj_class):
'''
Get timestamp for the given object and class.
'''
if obj is None or obj.id is None:
return None
o = self.db_fetch(obj.context, obj.id)
return getattr(o, self.attribute)
def __set__(self, obj, timestamp):
'''Update the timestamp for the given object.'''
if obj.id is None:
raise exception.ResourceNotAvailable(resource_name=obj.name)
o = self.db_fetch(obj.context, obj.id)
o.update_and_save({self.attribute: timestamp})