2b827e1e36
To make it possible to alter the runtime flow via a simple conditional like structure make it possible to have the graph flow link function take a decider that is expected to be some callable that will decide (via a boolean return) whether the edge should actually be traversed when running. When a decider returns false; the affected + successors will be set into the IGNORE state and they will be exempt from future runtime and scheduling decisions. Part of blueprint taskflow-conditional-execution Change-Id: Iab0ee46f86d6b8e747911174d54a7295b3fa404d
118 lines
4.1 KiB
Python
118 lines
4.1 KiB
Python
# -*- coding: utf-8 -*-
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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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from oslo_utils import reflection
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import six
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# Link metadata keys that have inherent/special meaning.
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#
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# This key denotes the link is an invariant that ensures the order is
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# correctly preserved.
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LINK_INVARIANT = 'invariant'
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# This key denotes the link is a manually/user-specified.
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LINK_MANUAL = 'manual'
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# This key denotes the link was created when resolving/compiling retries.
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LINK_RETRY = 'retry'
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# This key denotes the link was created due to symbol constraints and the
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# value will be a set of names that the constraint ensures are satisfied.
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LINK_REASONS = 'reasons'
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#
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# This key denotes a callable that will determine if the target is visited.
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LINK_DECIDER = 'decider'
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@six.add_metaclass(abc.ABCMeta)
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class Flow(object):
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"""The base abstract class of all flow implementations.
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A flow is a structure that defines relationships between tasks. You can
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add tasks and other flows (as subflows) to the flow, and the flow provides
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a way to implicitly or explicitly define how they are interdependent.
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Exact structure of the relationships is defined by concrete
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implementation, while this class defines common interface and adds
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human-readable (not necessary unique) name.
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NOTE(harlowja): if a flow is placed in another flow as a subflow, a desired
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way to compose flows together, then it is valid and permissible that during
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compilation the subflow & parent flow *may* be flattened into a new flow.
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"""
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def __init__(self, name, retry=None):
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self._name = six.text_type(name)
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self._retry = retry
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# NOTE(akarpinska): if retry doesn't have a name,
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# the name of its owner will be assigned
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if self._retry is not None and self._retry.name is None:
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self._retry.name = self.name + "_retry"
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@property
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def name(self):
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"""A non-unique name for this flow (human readable)."""
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return self._name
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@property
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def retry(self):
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"""The associated flow retry controller.
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This retry controller object will affect & control how (and if) this
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flow and its contained components retry when execution is underway and
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a failure occurs.
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"""
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return self._retry
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@abc.abstractmethod
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def add(self, *items):
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"""Adds a given item/items to this flow."""
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@abc.abstractmethod
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def __len__(self):
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"""Returns how many items are in this flow."""
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@abc.abstractmethod
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def __iter__(self):
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"""Iterates over the children of the flow."""
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@abc.abstractmethod
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def iter_links(self):
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"""Iterates over dependency links between children of the flow.
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Iterates over 3-tuples ``(A, B, meta)``, where
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* ``A`` is a child (atom or subflow) link starts from;
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* ``B`` is a child (atom or subflow) link points to; it is
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said that ``B`` depends on ``A`` or ``B`` requires ``A``;
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* ``meta`` is link metadata, a dictionary.
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"""
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def __str__(self):
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return "%s: %s(len=%d)" % (reflection.get_class_name(self),
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self.name, len(self))
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@property
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def provides(self):
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"""Set of symbol names provided by the flow."""
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provides = set()
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if self._retry is not None:
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provides.update(self._retry.provides)
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for item in self:
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provides.update(item.provides)
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return frozenset(provides)
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@abc.abstractproperty
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def requires(self):
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"""Set of *unsatisfied* symbol names required by the flow."""
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