3a8a78ee64
Instead of using strings (which can be easy to mistype and get wrong), provide a set of constants that can be used to attach and use these keys in flows and at compilation. This also helps make it more clear what the keys do and where they are used. Change-Id: I5283b27617961136a4582bbcfce4617f05e8dd1d
117 lines
4.1 KiB
Python
117 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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import six
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from taskflow.utils import reflection
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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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@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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lines = ["%s: %s" % (reflection.get_class_name(self), self.name)]
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lines.append("%s" % (len(self)))
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return "; ".join(lines)
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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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