1011df951e
In addition to iteration over its children (atoms or subflows) each pattern now provides iter_links() method that iterates over dependency links. This allows engines to treat all patterns in the same way instead knowing what structure each pattern expresses. Change-Id: I52cb5b0b501eefc8eb56a9ef5303aeb318013e11
104 lines
3.6 KiB
Python
104 lines
3.6 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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@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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execution the subflow & parent flow may be flattened into a new flow. Since
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a flow is just a 'structuring' concept this is typically a behavior that
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should not be worried about (as it is not visible to the user), but it is
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worth mentioning here.
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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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# 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:
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self._retry_provides = self.retry.provides
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self._retry_requires = self.retry.requires
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if not self._retry.name:
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self._retry.set_name(self.name + "_retry")
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else:
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self._retry_provides = set()
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self._retry_requires = set()
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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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"""A retry object that will affect control how (and if) this flow
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retries while execution is underway.
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"""
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return self._retry
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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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@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.abstractproperty
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def requires(self):
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"""Browse argument requirement names this flow requires to run."""
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@abc.abstractproperty
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def provides(self):
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"""Browse argument names provided by the flow."""
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