1d983f5c31
Move the final logic of the compilation stage (and pre-run) code into a new engine stage that is devoted to performing post-compile but pre-run actions. Do the final validation that was being done in compile() and run() in this stage instead of being split across those two stages. Breaking change: any user expecting storage to be ensured after compilation will have to adjust their code to call prepare (after which they can continue to expect storage to be ready). Change-Id: Ie97bc4a795266dda9d7ae8b395bcaadcd1ada737
82 lines
2.6 KiB
Python
82 lines
2.6 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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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._storage = None
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self.notifier = misc.TransitionNotifier()
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self.task_notifier = misc.TransitionNotifier()
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@property
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def storage(self):
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"""The storage unit for this flow."""
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if self._storage is None:
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self._storage = self._storage_cls(self._flow_detail, self._backend)
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return self._storage
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@abc.abstractproperty
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def _storage_cls(self):
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"""Storage class 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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