63 lines
2.3 KiB
Python
63 lines
2.3 KiB
Python
# -*- coding: utf-8 -*-
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# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import abc
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class Task(object):
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"""An abstraction that defines a potential piece of work that can be
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applied and can be reverted to undo the work as a single unit.
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"""
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__metaclass__ = abc.ABCMeta
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def __init__(self, name):
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self.name = name
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# Identifying items that this task requires to apply.
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self._requires = set()
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# Identifying items that this task provides from its apply.
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self._provides = set()
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def __str__(self):
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return "Task: %s" % (self.name)
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def requires(self):
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"""Returns an *immutable* input 'resource' name set this task depends
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on existing before this task can be applied."""
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return self._requires
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def provides(self):
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"""Returns an *immutable* output 'resource' name set this task
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produces that other tasks may depend on this task providing."""
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return self._provides
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@abc.abstractmethod
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def apply(self, context, *args, **kwargs):
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"""Activate a given task which will perform some operation and return.
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This method can be used to apply some given context and given set
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of args and kwargs to accomplish some goal. Note that the result
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that is returned needs to be serializable so that it can be passed
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back into this task if reverting is triggered."""
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raise NotImplementedError()
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def revert(self, context, result, cause):
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"""Revert this task using the given context, result that the apply
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provided as well as any information which may have caused
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said reversion."""
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pass
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