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
[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]@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."""
[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 = 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)
[docs]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
[docs]@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
[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 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):
@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
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