b07ee63f78
When flow is being constructed we ensure that it is actually valid by checking its invariants: - for linear flow, no item should depend on items that are executed after it; - for unordered flow, items should be independent. We also add check that all necessary provides were injected to storage before actually running flow. Implements: blueprint flow-verification Change-Id: I499898f543505b7dd6f82716ae8f4011cb08f601
80 lines
2.6 KiB
Python
80 lines
2.6 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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from taskflow import exceptions
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from taskflow import flow
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class Flow(flow.Flow):
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""""Linear Flow pattern.
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A linear (potentially nested) flow of *tasks/flows* that can be
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applied in order as one unit and rolled back as one unit using
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the reverse order that the *tasks/flows* have been applied in.
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NOTE(imelnikov): Tasks in should not depend on outputs
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of tasks that follow it in the flow.
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"""
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def __init__(self, name, uuid=None):
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super(Flow, self).__init__(name, uuid)
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self._children = []
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def add(self, *items):
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"""Adds a given task/tasks/flow/flows to this flow."""
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items = [self._extract_item(item) for item in items]
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# NOTE(imelnikov): we add item to the end of flow, so it should
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# not provide anything previous items of the flow require
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requires = self.requires
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for item in items:
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requires |= item.requires
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out_of_order = requires & item.provides
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if out_of_order:
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raise exceptions.InvariantViolationException(
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"%(item)s provides %(oo)s that are required "
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"by previous item(s) of linear flow %(flow)s"
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% dict(item=item.name, flow=self.name,
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oo=sorted(out_of_order)))
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self._children.extend(items)
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return self
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def __len__(self):
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return len(self._children)
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def __iter__(self):
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for child in self._children:
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yield child
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@property
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def provides(self):
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provides = set()
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for subflow in self._children:
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provides.update(subflow.provides)
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return provides
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@property
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def requires(self):
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requires = set()
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provides = set()
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for subflow in self._children:
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requires.update(subflow.requires - provides)
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provides.update(subflow.provides)
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return requires
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