# -*- coding: utf-8 -*- # Copyright (C) 2013 Rackspace Hosting Inc. All Rights Reserved. # 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 from oslo_utils import uuidutils import six from taskflow.types import notifier @six.add_metaclass(abc.ABCMeta) class Job(object): """A abstraction that represents a named and trackable unit of work. A job connects a logbook, a owner, last modified and created on dates and any associated state that the job has. Since it is a connector to a logbook, which are each associated with a set of factories that can create set of flows, it is the current top-level container for a piece of work that can be owned by an entity (typically that entity will read those logbooks and run any contained flows). Only one entity will be allowed to own and operate on the flows contained in a job at a given time (for the foreseeable future). NOTE(harlowja): It is the object that will be transferred to another entity on failure so that the contained flows ownership can be transferred to the secondary entity/owner for resumption, continuation, reverting... """ def __init__(self, name, uuid=None, details=None): if uuid: self._uuid = uuid else: self._uuid = uuidutils.generate_uuid() self._name = name if not details: details = {} self._details = details @abc.abstractproperty def last_modified(self): """The datetime the job was last modified.""" pass @abc.abstractproperty def created_on(self): """The datetime the job was created on.""" pass @abc.abstractproperty def board(self): """The board this job was posted on or was created from.""" @abc.abstractproperty def state(self): """The current state of this job.""" @abc.abstractproperty def book(self): """Logbook associated with this job. If no logbook is associated with this job, this property is None. """ @abc.abstractproperty def book_uuid(self): """UUID of logbook associated with this job. If no logbook is associated with this job, this property is None. """ @abc.abstractproperty def book_name(self): """Name of logbook associated with this job. If no logbook is associated with this job, this property is None. """ @property def uuid(self): """The uuid of this job.""" return self._uuid @property def details(self): """A dictionary of any details associated with this job.""" return self._details @property def name(self): """The non-uniquely identifying name of this job.""" return self._name def __str__(self): """Pretty formats the job into something *more* meaningful.""" return "%s %s (%s): %s" % (type(self).__name__, self.name, self.uuid, self.details) @six.add_metaclass(abc.ABCMeta) class JobBoard(object): """A place where jobs can be posted, reposted, claimed and transferred. There can be multiple implementations of this job board, depending on the desired semantics and capabilities of the underlying jobboard implementation. NOTE(harlowja): the name is meant to be an analogous to a board/posting system that is used in newspapers, or elsewhere to solicit jobs that people can interview and apply for (and then work on & complete). """ def __init__(self, name, conf): self._name = name self._conf = conf @abc.abstractmethod def iterjobs(self, only_unclaimed=False, ensure_fresh=False): """Returns an iterator of jobs that are currently on this board. NOTE(harlowja): the ordering of this iteration should be by posting order (oldest to newest) if possible, but it is left up to the backing implementation to provide the order that best suits it (so don't depend on it always being oldest to newest). NOTE(harlowja): the iterator that is returned may support other attributes which can be used to further customize how iteration can be accomplished; check with the backends iterator object to determine what other attributes are supported. :param only_unclaimed: boolean that indicates whether to only iteration over unclaimed jobs. :param ensure_fresh: boolean that requests to only iterate over the most recent jobs available, where the definition of what is recent is backend specific. It is allowable that a backend may ignore this value if the backends internal semantics/capabilities can not support this argument. """ @abc.abstractmethod def wait(self, timeout=None): """Waits a given amount of time for jobs to be posted. When jobs are found then an iterator will be returned that can be used to iterate over those jobs. NOTE(harlowja): since a jobboard can be mutated on by multiple external entities at the *same* time the iterator that can be returned *may* still be empty due to other entities removing those jobs after the iterator has been created (be aware of this when using it). :param timeout: float that indicates how long to wait for a job to appear (if None then waits forever). """ @abc.abstractproperty def job_count(self): """Returns how many jobs are on this jobboard. NOTE(harlowja): this count may change as jobs appear or are removed so the accuracy of this count should not be used in a way that requires it to be exact & absolute. """ @abc.abstractmethod def find_owner(self, job): """Gets the owner of the job if one exists.""" @property def name(self): """The non-uniquely identifying name of this jobboard.""" return self._name @abc.abstractmethod def consume(self, job, who): """Permanently (and atomically) removes a job from the jobboard. Consumption signals to the board (and any others examining the board) that this job has been completed by the entity that previously claimed that job. Only the entity that has claimed that job is able to consume the job. A job that has been consumed can not be reclaimed or reposted by another entity (job postings are immutable). Any entity consuming a unclaimed job (or a job they do not have a claim on) will cause an exception. :param job: a job on this jobboard that can be consumed (if it does not exist then a NotFound exception will be raised). :param who: string that names the entity performing the consumption, this must be the same name that was used for claiming this job. """ @abc.abstractmethod def post(self, name, book=None, details=None): """Atomically creates and posts a job to the jobboard. This posting allowing others to attempt to claim that job (and subsequently work on that job). The contents of the provided logbook, details dictionary, or name (or a mix of these) must provide *enough* information for consumers to reference to construct and perform that jobs contained work (whatever it may be). Once a job has been posted it can only be removed by consuming that job (after that job is claimed). Any entity can post/propose jobs to the jobboard (in the future this may be restricted). Returns a job object representing the information that was posted. """ @abc.abstractmethod def claim(self, job, who): """Atomically attempts to claim the provided job. If a job is claimed it is expected that the entity that claims that job will at sometime in the future work on that jobs contents and either fail at completing them (resulting in a reposting) or consume that job from the jobboard (signaling its completion). If claiming fails then a corresponding exception will be raised to signal this to the claim attempter. :param job: a job on this jobboard that can be claimed (if it does not exist then a NotFound exception will be raised). :param who: string that names the claiming entity. """ @abc.abstractmethod def abandon(self, job, who): """Atomically attempts to abandon the provided job. This abandonment signals to others that the job may now be reclaimed. This would typically occur if the entity that has claimed the job has failed or is unable to complete the job or jobs it had previously claimed. Only the entity that has claimed that job can abandon a job. Any entity abandoning a unclaimed job (or a job they do not own) will cause an exception. :param job: a job on this jobboard that can be abandoned (if it does not exist then a NotFound exception will be raised). :param who: string that names the entity performing the abandoning, this must be the same name that was used for claiming this job. """ @abc.abstractproperty def connected(self): """Returns if this jobboard is connected.""" @abc.abstractmethod def connect(self): """Opens the connection to any backend system.""" @abc.abstractmethod def close(self): """Close the connection to any backend system. Once closed the jobboard can no longer be used (unless reconnection occurs). """ # Jobboard events POSTED = 'POSTED' # new job is/has been posted REMOVAL = 'REMOVAL' # existing job is/has been removed class NotifyingJobBoard(JobBoard): """A jobboard subclass that can notify others about board events. Implementers are expected to notify *at least* about jobs being posted and removed. NOTE(harlowja): notifications that are emitted *may* be emitted on a separate dedicated thread when they occur, so ensure that all callbacks registered are thread safe (and block for as little time as possible). """ def __init__(self, name, conf): super(NotifyingJobBoard, self).__init__(name, conf) self.notifier = notifier.Notifier()