9443506b93
"_with" is kind of obvious, and also less typing for users of this library Change-Id: I99f597dae5612cc44cc7f19ae144776f63d32bac
141 lines
5.2 KiB
Python
141 lines
5.2 KiB
Python
# -*- coding: utf-8 -*-
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# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright (C) 2013 Rackspace Hosting Inc. All Rights Reserved.
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# Copyright (C) 2013 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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from taskflow import utils
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class BaseTask(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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# 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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self.requires = set()
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# An *immutable* input 'resource' name set this task would like to
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# depends on existing before this task can be applied (but does not
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# strongly depend on existing).
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self.optional = set()
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# 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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self.provides = set()
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# This identifies the version of the task to be ran which
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# can be useful in resuming older versions of tasks. Standard
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# major, minor version semantics apply.
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self.version = (1, 0)
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@property
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def name(self):
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return self._name
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def __str__(self):
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return "%s==%s" % (self.name, utils.get_task_version(self))
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@abc.abstractmethod
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def __call__(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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"""
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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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"""
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class Task(BaseTask):
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"""Base class for user-defined tasks
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Adds following features to Task:
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- auto-generates name from type of self
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- adds all __call__ argument names to task requiremets
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"""
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def __init__(self, name=None, requires_from_args=True):
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"""Initialize task instance
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:param name: task name, if None (the default) name will
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be autogenerated
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:param requires_from_args: if True (the default) __call__
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arguments names will be added to task requirements
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"""
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if name is None:
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name = utils.get_callable_name(self)
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super(Task, self).__init__(name)
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if requires_from_args:
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f_args = utils.get_required_callable_args(self)
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self.requires.update(a for a in f_args if a != 'context')
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class FunctorTask(BaseTask):
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"""Adaptor to make task from a callable
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Take any callable and make a task from it.
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"""
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def __init__(self, execute, **kwargs):
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"""Initialize FunctorTask instance with given callable and kwargs
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:param execute: the callable
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:param kwargs: reserved keywords (all optional) are
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name: name of the task, default None (auto generate)
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revert: the callable to revert, default None
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version: version of the task, default Task's version 1.0
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optionals: optionals of the task, default ()
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provides: provides of the task, default ()
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requires: requires of the task, default ()
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auto_extract: auto extract execute's args and put it into
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requires, default True
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"""
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name = kwargs.pop('name', None)
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if name is None:
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name = utils.get_callable_name(execute)
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super(FunctorTask, self).__init__(name)
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self._execute = execute
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self._revert = kwargs.pop('revert', None)
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self.version = kwargs.pop('version', self.version)
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self.optional.update(kwargs.pop('optional', ()))
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self.provides.update(kwargs.pop('provides', ()))
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self.requires.update(kwargs.pop('requires', ()))
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if kwargs.pop('auto_extract', True):
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f_args = utils.get_required_callable_args(execute)
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self.requires.update(a for a in f_args if a != 'context')
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if kwargs:
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raise TypeError('__init__() got an unexpected keyword argument %r'
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% kwargs.keys[0])
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def __call__(self, *args, **kwargs):
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return self._execute(*args, **kwargs)
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def revert(self, *args, **kwargs):
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if self._revert:
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return self._revert(*args, **kwargs)
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else:
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return None
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