134 lines
4.7 KiB
Python
134 lines
4.7 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.types import notifier
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from taskflow.utils import misc
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@six.add_metaclass(abc.ABCMeta)
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class Engine(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 atom_notifier: A notification object that will dispatch events that
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occur related to the atoms the engine contains.
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"""
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def __init__(self, flow, flow_detail, backend, options):
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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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self._options = misc.safe_copy_dict(options)
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self._notifier = notifier.Notifier()
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self._atom_notifier = notifier.Notifier()
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@property
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def notifier(self):
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"""The flow notifier."""
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return self._notifier
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@property
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def atom_notifier(self):
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"""The atom notifier."""
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return self._atom_notifier
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@property
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def options(self):
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"""The options that were passed to this engine on construction."""
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return self._options
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@abc.abstractproperty
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def storage(self):
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"""The storage unit for this engine."""
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@abc.abstractproperty
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def statistics(self):
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"""A dictionary of runtime statistics this engine has gathered.
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This dictionary will be empty when the engine has never been
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ran. When it is running or has ran previously it should have (but
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may not) have useful and/or informational keys and values when
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running is underway and/or completed.
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.. warning:: The keys in this dictionary **should** be some what
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stable (not changing), but there existence **may**
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change between major releases as new statistics are
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gathered or removed so before accessing keys ensure that
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they actually exist and handle when they do not.
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"""
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@abc.abstractmethod
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def compile(self):
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"""Compiles the contained flow into a internal representation.
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This internal representation is what the engine will *actually* use to
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run. If this compilation can not be accomplished then an exception
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is expected to be thrown with a message indicating why the compilation
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could not be achieved.
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"""
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@abc.abstractmethod
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def reset(self):
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"""Reset back to the ``PENDING`` state.
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If a flow had previously ended up (from a prior engine
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:py:func:`.run`) in the ``FAILURE``, ``SUCCESS`` or ``REVERTED``
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states (or for some reason it ended up in an intermediary state) it
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can be desirable to make it possible to run it again. Calling this
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method enables that to occur (without causing a state transition
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failure, which would typically occur if :py:meth:`.run` is called
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directly without doing a reset).
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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, the atoms will be reset and
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the engine will enter the ``PENDING`` state.
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"""
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@abc.abstractmethod
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def validate(self):
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"""Performs any pre-run, post-prepare validation actions.
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NOTE(harlowja): During validation all final dependencies
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will be verified and ensured. This will by default check that all
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atoms have satisfiable requirements (satisfied by some other
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provider).
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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 atoms then this will attempt to
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suspend future work from being started (currently active atoms 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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