Files
deb-python-taskflow/taskflow/engines/base.py
Joshua Harlow d433a5323f Deprecate engine_conf and prefer engine instead
To avoid having one set of options coming from `engine_conf`
and another set of options coming from `kwargs` and another set
coming from `engine_conf` if it is a URI just start to shift
toward `engine_conf` being deprecated and `engine` being a string
type only (or a URI with additional query parameters) and having
any additional **kwargs that are provided just get merged into the
final engine options.

This adds a new helper function that handles all these various
options and adds in a keyword argument `engine` that will be shifted
to in a future version (in that future version we can also then
remove the `engine_conf` and just stick to a smaller set of option
mechanisms).

It also adjusts all examples to use this new and more easier to
understand format and adjusts tests, conductor interface to use
this new more easily understandable style of getting an engine.

Change-Id: Ic7617057338e0c63775cf38a24643cff6e454950
2014-10-18 13:28:27 -07:00

93 lines
3.1 KiB
Python

# -*- coding: utf-8 -*-
# Copyright (C) 2013 Yahoo! Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import abc
import six
from taskflow.utils import misc
@six.add_metaclass(abc.ABCMeta)
class EngineBase(object):
"""Base for all engines implementations.
:ivar notifier: A notification object that will dispatch events that
occur related to the flow the engine contains.
:ivar task_notifier: A notification object that will dispatch events that
occur related to the tasks the engine contains.
"""
def __init__(self, flow, flow_detail, backend, options):
self._flow = flow
self._flow_detail = flow_detail
self._backend = backend
if not options:
self._options = {}
else:
self._options = dict(options)
self.notifier = misc.Notifier()
self.task_notifier = misc.Notifier()
@property
def options(self):
"""The options that were passed to this engine on construction."""
return self._options
@misc.cachedproperty
def storage(self):
"""The storage unit for this flow."""
return self._storage_factory(self._flow_detail, self._backend)
@abc.abstractproperty
def _storage_factory(self):
"""Storage factory that will be used to generate storage objects."""
@abc.abstractmethod
def compile(self):
"""Compiles the contained flow into a internal representation.
This internal representation is what the engine will *actually* use to
run. If this compilation can not be accomplished then an exception
is expected to be thrown with a message indicating why the compilation
could not be achieved.
"""
@abc.abstractmethod
def prepare(self):
"""Performs any pre-run, but post-compilation actions.
NOTE(harlowja): During preparation it is currently assumed that the
underlying storage will be initialized, all final dependencies
will be verified, the tasks will be reset and the engine will enter
the PENDING state.
"""
@abc.abstractmethod
def run(self):
"""Runs the flow in the engine to completion (or die trying)."""
@abc.abstractmethod
def suspend(self):
"""Attempts to suspend the engine.
If the engine is currently running tasks then this will attempt to
suspend future work from being started (currently active tasks can
not currently be preempted) and move the engine into a suspend state
which can then later be resumed from.
"""