fa46708c0e
Instead of requiring iteration to be able to list new jobs and existing jobs so that they can be claimed, allow for attaching callbacks to the jobboard where instead of requiring iteration those callbacks will be automatically called by the jobboard internally when events are recieved. Breaking change: renames transition notifier to notifier since it is really not just a notifier for transitions but is a generic notifier of events occuring (and details about those events). This is an internal api so its not expected that this will cause any issues (it's not expected for external users to be creating instances of this class). Implements bp board-notification Change-Id: I2384d5e335ed9d17e29fec9a78699e3156fa225c
138 lines
5.3 KiB
Python
138 lines
5.3 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2013 Rackspace Hosting Inc. All Rights Reserved.
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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 JobBoard(object):
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"""A jobboard is an abstract representation of a place where jobs
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can be posted, reposted, claimed and transferred. There can be multiple
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implementations of this job board, depending on the desired semantics and
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capabilities of the underlying jobboard implementation.
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"""
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def __init__(self, name, conf):
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self._name = name
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self._conf = conf
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@abc.abstractmethod
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def iterjobs(self, only_unclaimed=False, ensure_fresh=False):
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"""Yields back jobs that are currently on this jobboard (claimed
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or not claimed).
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NOTE(harlowja): the ordering of this iteration should be by posting
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order (oldest to newest) if possible, but it is left up to the backing
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implementation to provide the order that best suits it (so don't depend
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on it always being oldest to newest).
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:param only_unclaimed: boolean that indicates whether to only iteration
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over unclaimed jobs.
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:param ensure_fresh: boolean that requests to only iterate over the
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most recent jobs available, where the definition of what is recent
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is backend specific. It is allowable that a backend may ignore this
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value if the backends internal semantics/capabilities can not
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support this argument.
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"""
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@abc.abstractproperty
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def job_count(self):
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"""Returns how many jobs are on this jobboard."""
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@abc.abstractmethod
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def find_owner(self, job):
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"""Gets the owner of the job if one exists."""
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@property
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def name(self):
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"""The non-uniquely identifying name of this jobboard."""
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return self._name
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@abc.abstractmethod
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def consume(self, job, who):
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"""Permanently (and atomically) removes a job from the jobboard,
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signaling that this job has been completed by the entity assigned
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to that job.
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Only the entity that has claimed that job is able to consume a job.
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A job that has been consumed can not be reclaimed or reposted by
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another entity (job postings are immutable). Any entity consuming
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a unclaimed job (or a job they do not own) will cause an exception.
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"""
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@abc.abstractmethod
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def post(self, name, book, details=None):
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"""Atomically creates and posts a job to the jobboard, allowing others
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to attempt to claim that job (and subsequently work on that job). The
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contents of the provided logbook must provide enough information for
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others to reference to construct & work on the desired entries that
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are contained in that logbook.
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Once a job has been posted it can only be removed by consuming that
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job (after that job is claimed). Any entity can post/propose jobs
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to the jobboard (in the future this may be restricted).
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Returns a job object representing the information that was posted.
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"""
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@abc.abstractmethod
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def claim(self, job, who):
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"""Atomically attempts to claim the given job for the entity and either
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succeeds or fails at claiming by throwing corresponding exceptions.
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If a job is claimed it is expected that the entity that claims that job
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will at sometime in the future work on that jobs flows and either fail
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at completing them (resulting in a reposting) or consume that job from
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the jobboard (signaling its completion).
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"""
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@abc.abstractmethod
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def abandon(self, job, who):
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"""Atomically abandons the given job on the jobboard, allowing that job
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to be reclaimed by others. This would typically occur if the entity
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that has claimed the job has failed or is unable to complete the job
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or jobs it has claimed.
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Only the entity that has claimed that job can abandon a job. Any entity
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abandoning a unclaimed job (or a job they do not own) will cause an
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exception.
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"""
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# Jobboard events
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POSTED = 'POSTED' # new job is/has been posted
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REMOVAL = 'REMOVAL' # existing job is/has been removed
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class NotifyingJobBoard(JobBoard):
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"""A jobboard subclass that can notify about jobs being created
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and removed, which can remove the repeated usage of iterjobs() to achieve
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the same operation.
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NOTE(harlowja): notifications that are emitted *may* be emitted on a
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separate dedicated thread when they occur, so ensure that all callbacks
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registered are thread safe.
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"""
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def __init__(self, name, conf):
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super(NotifyingJobBoard, self).__init__(name, conf)
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self.notifier = misc.Notifier()
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