Source code for

# -*- 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
#    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 collections
import contextlib
import functools
import time

import enum
from oslo_utils import timeutils
from oslo_utils import uuidutils

from taskflow import exceptions as excp
from taskflow import states
from taskflow.types import notifier
from taskflow.utils import iter_utils

[docs]class JobPriority(enum.Enum): """Enum of job priorities (modeled after hadoop job priorities).""" #: Extremely urgent job priority. VERY_HIGH = 'VERY_HIGH' #: Mildly urgent job priority. HIGH = 'HIGH' #: Default job priority. NORMAL = 'NORMAL' #: Not needed anytime soon job priority. LOW = 'LOW' #: Very much not needed anytime soon job priority. VERY_LOW = 'VERY_LOW' @classmethod def convert(cls, value): if isinstance(value, cls): return value try: return cls(value.upper()) except (ValueError, AttributeError): valids = [cls.VERY_HIGH, cls.HIGH, cls.NORMAL, cls.LOW, cls.VERY_LOW] valids = [p.value for p in valids] raise ValueError("'%s' is not a valid priority, valid" " priorities are %s" % (value, valids))
[docs] @classmethod def reorder(cls, *values): """Reorders (priority, value) tuples -> priority ordered values.""" if len(values) == 0: raise ValueError("At least one (priority, value) pair is" " required") elif len(values) == 1: v1 = values[0] # Even though this isn't used, we do the conversion because # all the other branches in this function do it so we do it # to be consistent (this also will raise on bad values, which # we want to do)... p1 = cls.convert(v1[0]) return v1[1] else: # Order very very much matters in this tuple... priority_ordering = (cls.VERY_HIGH, cls.HIGH, cls.NORMAL, cls.LOW, cls.VERY_LOW) if len(values) == 2: # It's common to use this in a 2 tuple situation, so # make it avoid all the needed complexity that is done # for greater than 2 tuples. v1 = values[0] v2 = values[1] p1 = cls.convert(v1[0]) p2 = cls.convert(v2[0]) p1_i = priority_ordering.index(p1) p2_i = priority_ordering.index(p2) if p1_i <= p2_i: return v1[1], v2[1] else: return v2[1], v1[1] else: buckets = collections.defaultdict(list) for (p, v) in values: p = cls.convert(p) buckets[p].append(v) values = [] for p in priority_ordering: values.extend(buckets[p]) return tuple(values)
[docs]class Job(object, metaclass=abc.ABCMeta): """A abstraction that represents a named and trackable unit of work. A job connects a logbook, a owner, a priority, last modified and created on dates and any associated state that the job has. Since it is a connected 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, board, name, uuid=None, details=None, backend=None, book=None, book_data=None): if uuid: self._uuid = uuid else: self._uuid = uuidutils.generate_uuid() self._name = name if not details: details = {} self._details = details self._backend = backend self._board = board self._book = book if not book_data: book_data = {} self._book_data = book_data @abc.abstractproperty def last_modified(self): """The datetime the job was last modified.""" @abc.abstractproperty def created_on(self): """The datetime the job was created on.""" @property def board(self): """The board this job was posted on or was created from.""" return self._board @abc.abstractproperty def state(self): """Access the current state of this job.""" @abc.abstractproperty def priority(self): """The :py:class:`~.JobPriority` of this job."""
[docs] def wait(self, timeout=None, delay=0.01, delay_multiplier=2.0, max_delay=60.0, sleep_func=time.sleep): """Wait for job to enter completion state. If the job has not completed in the given timeout, then return false, otherwise return true (a job failure exception may also be raised if the job information can not be read, for whatever reason). Periodic state checks will happen every ``delay`` seconds where ``delay`` will be multiplied by the given multipler after a state is found that is **not** complete. Note that if no timeout is given this is equivalent to blocking until the job has completed. Also note that if a jobboard backend can optimize this method then its implementation may not use delays (and backoffs) at all. In general though no matter what optimizations are applied implementations must **always** respect the given timeout value. """ if timeout is not None: w = timeutils.StopWatch(duration=timeout) w.start() else: w = None delay_gen = iter_utils.generate_delays(delay, max_delay, multiplier=delay_multiplier) while True: if w is not None and w.expired(): return False if self.state == states.COMPLETE: return True sleepy_secs = next(delay_gen) if w is not None: sleepy_secs = min(w.leftover(), sleepy_secs) sleep_func(sleepy_secs) return False
@property def book(self): """Logbook associated with this job. If no logbook is associated with this job, this property is None. """ if self._book is None: self._book = self._load_book() return self._book @property def book_uuid(self): """UUID of logbook associated with this job. If no logbook is associated with this job, this property is None. """ if self._book is not None: return self._book.uuid else: return self._book_data.get('uuid') @property def book_name(self): """Name of logbook associated with this job. If no logbook is associated with this job, this property is None. """ if self._book is not None: return else: return self._book_data.get('name') @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 _load_book(self): book_uuid = self.book_uuid if self._backend is not None and book_uuid is not None: # TODO(harlowja): we are currently limited by assuming that the # job posted has the same backend as this loader (to start this # seems to be a ok assumption, and can be adjusted in the future # if we determine there is a use-case for multi-backend loaders, # aka a registry of loaders). with contextlib.closing(self._backend.get_connection()) as conn: return conn.get_logbook(book_uuid) # No backend to fetch from or no uuid specified return None def __str__(self): """Pretty formats the job into something *more* meaningful.""" cls_name = type(self).__name__ return "%s: %s (priority=%s, uuid=%s, details=%s)" % ( cls_name,, self.priority, self.uuid, self.details)
[docs]class JobBoardIterator(object): """Iterator over a jobboard that iterates over potential jobs. It provides the following attributes: * ``only_unclaimed``: boolean that indicates whether to only iterate over unclaimed jobs * ``ensure_fresh``: boolean that requests that during every fetch of a new set of jobs this will cause the iterator to force the backend to refresh (ensuring that the jobboard has the most recent job listings) * ``board``: the board this iterator was created from """ _UNCLAIMED_JOB_STATES = (states.UNCLAIMED,) _JOB_STATES = (states.UNCLAIMED, states.COMPLETE, states.CLAIMED) def __init__(self, board, logger, board_fetch_func=None, board_removal_func=None, only_unclaimed=False, ensure_fresh=False): self._board = board self._logger = logger self._board_removal_func = board_removal_func self._board_fetch_func = board_fetch_func self._fetched = False self._jobs = collections.deque() self.only_unclaimed = only_unclaimed self.ensure_fresh = ensure_fresh @property def board(self): """The board this iterator was created from.""" return self._board def __iter__(self): return self def _next_job(self): if self.only_unclaimed: allowed_states = self._UNCLAIMED_JOB_STATES else: allowed_states = self._JOB_STATES job = None while self._jobs and job is None: maybe_job = self._jobs.popleft() try: if maybe_job.state in allowed_states: job = maybe_job except excp.JobFailure: self._logger.warn("Failed determining the state of" " job '%s'", maybe_job, exc_info=True) except excp.NotFound: # Attempt to clean this off the board now that we found # it wasn't really there (this **must** gracefully handle # removal already having happened). if self._board_removal_func is not None: self._board_removal_func(maybe_job) return job def __next__(self): if not self._jobs: if not self._fetched: if self._board_fetch_func is not None: self._jobs.extend( self._board_fetch_func( ensure_fresh=self.ensure_fresh)) self._fetched = True job = self._next_job() if job is None: raise StopIteration else: return job
[docs]class JobBoard(object, metaclass=abc.ABCMeta): """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
[docs] @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) with higher priority jobs being provided before lower priority jobs, but it is left up to the backing implementation to provide the order that best suits it.. 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. """
[docs] @abc.abstractmethod def wait(self, timeout=None): """Waits a given amount of time for **any** 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. """
[docs] @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
[docs] @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. """
[docs] @abc.abstractmethod def post(self, name, book=None, details=None, priority=JobPriority.NORMAL): """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. """
[docs] @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. """
[docs] @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. """
[docs] @abc.abstractmethod def trash(self, job, who): """Trash the provided job. Trashing a job signals to others that the job is broken and should not be reclaimed. This is provided as an option for users to be able to remove jobs from the board externally. The trashed job details should be kept around in an alternate location to be reviewed, if desired. Only the entity that has claimed that job can trash a job. Any entity trashing a unclaimed job (or a job they do not own) will cause an exception. :param job: a job on this jobboard that can be trashed (if it does not exist then a NotFound exception will be raised). :param who: string that names the entity performing the trashing, this must be the same name that was used for claiming this job. """
[docs] @abc.abstractmethod def register_entity(self, entity): """Register an entity to the jobboard('s backend), e.g: a conductor. :param entity: entity to register as being associated with the jobboard('s backend) :type entity: :py:class:`~taskflow.types.entity.Entity` """
@abc.abstractproperty def connected(self): """Returns if this jobboard is connected."""
[docs] @abc.abstractmethod def connect(self): """Opens the connection to any backend system."""
[docs] @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
[docs]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()
# Internal helpers for usage by board implementations... def check_who(meth): @functools.wraps(meth) def wrapper(self, job, who, *args, **kwargs): if not isinstance(who, str): raise TypeError("Job applicant must be a string type") if len(who) == 0: raise ValueError("Job applicant must be non-empty") return meth(self, job, who, *args, **kwargs) return wrapper def format_posting(uuid, name, created_on=None, last_modified=None, details=None, book=None, priority=JobPriority.NORMAL): posting = { 'uuid': uuid, 'name': name, 'priority': priority.value, } if created_on is not None: posting['created_on'] = created_on if last_modified is not None: posting['last_modified'] = last_modified if details: posting['details'] = details else: posting['details'] = {} if book is not None: posting['book'] = { 'name':, 'uuid': book.uuid, } return posting