7477c243ca
Clean up the introduction where the notification mechanism is defined so that it becomes more clear what its usage is and what the attributes of an engine are that provide these capabilities. Change-Id: I4eeb9029b17d562111371c6f5155570b7a31859c
85 lines
2.8 KiB
Python
85 lines
2.8 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2013 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 misc
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@six.add_metaclass(abc.ABCMeta)
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class EngineBase(object):
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"""Base for all engines implementations.
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:ivar notifier: A notification object that will dispatch events that
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occur related to the flow the engine contains.
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:ivar task_notifier: A notification object that will dispatch events that
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occur related to the tasks the engine contains.
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"""
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def __init__(self, flow, flow_detail, backend, conf):
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self._flow = flow
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self._flow_detail = flow_detail
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self._backend = backend
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if not conf:
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self._conf = {}
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else:
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self._conf = dict(conf)
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self.notifier = misc.Notifier()
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self.task_notifier = misc.Notifier()
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@misc.cachedproperty
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def storage(self):
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"""The storage unit for this flow."""
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return self._storage_factory(self._flow_detail, self._backend)
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@abc.abstractproperty
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def _storage_factory(self):
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"""Storage factory that will be used to generate storage objects."""
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@abc.abstractmethod
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def compile(self):
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"""Compiles the contained flow into a structure which the engine can
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use to run or if this can not be done then an exception is thrown
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indicating why this compilation could not be achieved.
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"""
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@abc.abstractmethod
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def prepare(self):
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"""Performs any pre-run, but post-compilation actions.
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NOTE(harlowja): During preparation it is currently assumed that the
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underlying storage will be initialized, all final dependencies
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will be verified, the tasks will be reset and the engine will enter
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the PENDING state.
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"""
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@abc.abstractmethod
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def run(self):
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"""Runs the flow in the engine to completion (or die trying)."""
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@abc.abstractmethod
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def suspend(self):
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"""Attempts to suspend the engine.
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If the engine is currently running tasks then this will attempt to
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suspend future work from being started (currently active tasks can
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not currently be preempted) and move the engine into a suspend state
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which can then later be resumed from.
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"""
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