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# -*- coding: utf-8 -*-
# Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
#
# 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 taskflow import flow
_LINK_METADATA = {flow.LINK_INVARIANT: True}
class Flow(flow.Flow):
"""Linear flow pattern.
A linear (potentially nested) flow of *tasks/flows* that can be
applied in order as one unit and rolled back as one unit using
the reverse order that the *tasks/flows* have been applied in.
"""
def __init__(self, name, retry=None):
super(Flow, self).__init__(name, retry)
self._children = []
def add(self, *items):
"""Adds a given task/tasks/flow/flows to this flow."""
items = [i for i in items if i not in self._children]
self._children.extend(items)
return self
def __len__(self):
return len(self._children)
def __iter__(self):
for child in self._children:
yield child
@property
def requires(self):
requires = set()
prior_provides = set()
if self._retry is not None:
requires.update(self._retry.requires)
prior_provides.update(self._retry.provides)
for item in self:
requires.update(item.requires - prior_provides)
prior_provides.update(item.provides)
return frozenset(requires)
def iter_links(self):
for src, dst in zip(self._children[:-1], self._children[1:]):
yield (src, dst, _LINK_METADATA.copy())
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