# taskflow.jobs.base

# Source code for taskflow.jobs.base

    # -*- 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
    import collections
    import contextlib
    import time

    import enum
    from oslo_utils import timeutils
    from oslo_utils import uuidutils
    import six

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

    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))

        @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)

    @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, 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."""

        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 = six.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 self._book.name
            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.name, self.priority,
                self.uuid, self.details)

    class JobBoardIterator(six.Iterator):
        """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

    @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) 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.
            """

        @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.
            """

        @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, 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.
            """

        @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.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.
            """

        @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."""

        @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()

    # Internal helpers for usage by board implementations...

    def check_who(meth):

        @six.wraps(meth)
        def wrapper(self, job, who, *args, **kwargs):
            if not isinstance(who, six.string_types):
                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': book.name,
                'uuid': book.uuid,
            }
        return posting

this page last updated: 2020-04-10 14:06:26

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