This document describes the current stable version of Celery (3.1). For development docs, go here.
Source code for celery.beat
# -*- coding: utf-8 -*-
"""
celery.beat
~~~~~~~~~~~
The periodic task scheduler.
"""
from __future__ import absolute_import
import errno
import os
import time
import shelve
import sys
import traceback
from threading import Event, Thread
from billiard import ensure_multiprocessing
from billiard.process import Process
from billiard.common import reset_signals
from kombu.utils import cached_property, reprcall
from kombu.utils.functional import maybe_evaluate
from . import __version__
from . import platforms
from . import signals
from .five import items, reraise, values, monotonic
from .schedules import maybe_schedule, crontab
from .utils.imports import instantiate
from .utils.timeutils import humanize_seconds
from .utils.log import get_logger, iter_open_logger_fds
__all__ = ['SchedulingError', 'ScheduleEntry', 'Scheduler',
'PersistentScheduler', 'Service', 'EmbeddedService']
logger = get_logger(__name__)
debug, info, error, warning = (logger.debug, logger.info,
logger.error, logger.warning)
DEFAULT_MAX_INTERVAL = 300 # 5 minutes
[docs]class ScheduleEntry(object):
"""An entry in the scheduler.
:keyword name: see :attr:`name`.
:keyword schedule: see :attr:`schedule`.
:keyword args: see :attr:`args`.
:keyword kwargs: see :attr:`kwargs`.
:keyword options: see :attr:`options`.
:keyword last_run_at: see :attr:`last_run_at`.
:keyword total_run_count: see :attr:`total_run_count`.
:keyword relative: Is the time relative to when the server starts?
"""
#: The task name
name = None
#: The schedule (run_every/crontab)
schedule = None
#: Positional arguments to apply.
args = None
#: Keyword arguments to apply.
kwargs = None
#: Task execution options.
options = None
#: The time and date of when this task was last scheduled.
last_run_at = None
#: Total number of times this task has been scheduled.
total_run_count = 0
def __init__(self, name=None, task=None, last_run_at=None,
total_run_count=None, schedule=None, args=(), kwargs={},
options={}, relative=False, app=None):
self.app = app
self.name = name
self.task = task
self.args = args
self.kwargs = kwargs
self.options = options
self.schedule = maybe_schedule(schedule, relative, app=self.app)
self.last_run_at = last_run_at or self._default_now()
self.total_run_count = total_run_count or 0
def _default_now(self):
return self.schedule.now() if self.schedule else self.app.now()
def _next_instance(self, last_run_at=None):
"""Return a new instance of the same class, but with
its date and count fields updated."""
return self.__class__(**dict(
self,
last_run_at=last_run_at or self._default_now(),
total_run_count=self.total_run_count + 1,
))
__next__ = next = _next_instance # for 2to3
def __reduce__(self):
return self.__class__, (
self.name, self.task, self.last_run_at, self.total_run_count,
self.schedule, self.args, self.kwargs, self.options,
)
[docs] def update(self, other):
"""Update values from another entry.
Does only update "editable" fields (task, schedule, args, kwargs,
options).
"""
self.__dict__.update({'task': other.task, 'schedule': other.schedule,
'args': other.args, 'kwargs': other.kwargs,
'options': other.options})
[docs] def is_due(self):
"""See :meth:`~celery.schedule.schedule.is_due`."""
return self.schedule.is_due(self.last_run_at)
def __iter__(self):
return iter(items(vars(self)))
def __repr__(self):
return '<Entry: {0.name} {call} {0.schedule}'.format(
self,
call=reprcall(self.task, self.args or (), self.kwargs or {}),
)
[docs]class Scheduler(object):
"""Scheduler for periodic tasks.
The :program:`celery beat` program may instantiate this class
multiple times for introspection purposes, but then with the
``lazy`` argument set. It is important for subclasses to
be idempotent when this argument is set.
:keyword schedule: see :attr:`schedule`.
:keyword max_interval: see :attr:`max_interval`.
:keyword lazy: Do not set up the schedule.
"""
Entry = ScheduleEntry
#: The schedule dict/shelve.
schedule = None
#: Maximum time to sleep between re-checking the schedule.
max_interval = DEFAULT_MAX_INTERVAL
#: How often to sync the schedule (3 minutes by default)
sync_every = 3 * 60
#: How many tasks can be called before a sync is forced.
sync_every_tasks = None
_last_sync = None
_tasks_since_sync = 0
logger = logger # compat
def __init__(self, app, schedule=None, max_interval=None,
Publisher=None, lazy=False, sync_every_tasks=None, **kwargs):
self.app = app
self.data = maybe_evaluate({} if schedule is None else schedule)
self.max_interval = (max_interval or
app.conf.CELERYBEAT_MAX_LOOP_INTERVAL or
self.max_interval)
self.sync_every_tasks = (
app.conf.CELERYBEAT_SYNC_EVERY if sync_every_tasks is None
else sync_every_tasks)
self.Publisher = Publisher or app.amqp.TaskProducer
if not lazy:
self.setup_schedule()
[docs] def install_default_entries(self, data):
entries = {}
if self.app.conf.CELERY_TASK_RESULT_EXPIRES and \
not self.app.backend.supports_autoexpire:
if 'celery.backend_cleanup' not in data:
entries['celery.backend_cleanup'] = {
'task': 'celery.backend_cleanup',
'schedule': crontab('0', '4', '*'),
'options': {'expires': 12 * 3600}}
self.update_from_dict(entries)
[docs] def maybe_due(self, entry, publisher=None):
is_due, next_time_to_run = entry.is_due()
if is_due:
info('Scheduler: Sending due task %s (%s)', entry.name, entry.task)
try:
result = self.apply_async(entry, publisher=publisher)
except Exception as exc:
error('Message Error: %s\n%s',
exc, traceback.format_stack(), exc_info=True)
else:
debug('%s sent. id->%s', entry.task, result.id)
return next_time_to_run
[docs] def tick(self):
"""Run a tick, that is one iteration of the scheduler.
Executes all due tasks.
"""
remaining_times = []
try:
for entry in values(self.schedule):
next_time_to_run = self.maybe_due(entry, self.publisher)
if next_time_to_run:
remaining_times.append(next_time_to_run)
except RuntimeError:
pass
return min(remaining_times + [self.max_interval])
[docs] def should_sync(self):
return (
(not self._last_sync or
(monotonic() - self._last_sync) > self.sync_every) or
(self.sync_every_tasks and
self._tasks_since_sync >= self.sync_every_tasks)
)
[docs] def reserve(self, entry):
new_entry = self.schedule[entry.name] = next(entry)
return new_entry
[docs] def apply_async(self, entry, publisher=None, **kwargs):
# Update timestamps and run counts before we actually execute,
# so we have that done if an exception is raised (doesn't schedule
# forever.)
entry = self.reserve(entry)
task = self.app.tasks.get(entry.task)
try:
if task:
result = task.apply_async(entry.args, entry.kwargs,
publisher=publisher,
**entry.options)
else:
result = self.send_task(entry.task, entry.args, entry.kwargs,
publisher=publisher,
**entry.options)
except Exception as exc:
reraise(SchedulingError, SchedulingError(
"Couldn't apply scheduled task {0.name}: {exc}".format(
entry, exc=exc)), sys.exc_info()[2])
finally:
self._tasks_since_sync += 1
if self.should_sync():
self._do_sync()
return result
def _do_sync(self):
try:
debug('beat: Synchronizing schedule...')
self.sync()
finally:
self._last_sync = monotonic()
self._tasks_since_sync = 0
[docs] def add(self, **kwargs):
entry = self.Entry(app=self.app, **kwargs)
self.schedule[entry.name] = entry
return entry
def _maybe_entry(self, name, entry):
if isinstance(entry, self.Entry):
entry.app = self.app
return entry
return self.Entry(**dict(entry, name=name, app=self.app))
[docs] def update_from_dict(self, dict_):
self.schedule.update(dict(
(name, self._maybe_entry(name, entry))
for name, entry in items(dict_)))
[docs] def merge_inplace(self, b):
schedule = self.schedule
A, B = set(schedule), set(b)
# Remove items from disk not in the schedule anymore.
for key in A ^ B:
schedule.pop(key, None)
# Update and add new items in the schedule
for key in B:
entry = self.Entry(**dict(b[key], name=key, app=self.app))
if schedule.get(key):
schedule[key].update(entry)
else:
schedule[key] = entry
def _ensure_connected(self):
# callback called for each retry while the connection
# can't be established.
def _error_handler(exc, interval):
error('beat: Connection error: %s. '
'Trying again in %s seconds...', exc, interval)
return self.connection.ensure_connection(
_error_handler, self.app.conf.BROKER_CONNECTION_MAX_RETRIES
)
schedule = property(get_schedule, set_schedule)
@cached_property
@cached_property
@property
def info(self):
return ''
[docs]class PersistentScheduler(Scheduler):
persistence = shelve
known_suffixes = ('', '.db', '.dat', '.bak', '.dir')
_store = None
def __init__(self, *args, **kwargs):
self.schedule_filename = kwargs.get('schedule_filename')
Scheduler.__init__(self, *args, **kwargs)
def _remove_db(self):
for suffix in self.known_suffixes:
with platforms.ignore_errno(errno.ENOENT):
os.remove(self.schedule_filename + suffix)
def _open_schedule(self):
return self.persistence.open(self.schedule_filename, writeback=True)
def _destroy_open_corrupted_schedule(self, exc):
error('Removing corrupted schedule file %r: %r',
self.schedule_filename, exc, exc_info=True)
self._remove_db()
return self._open_schedule()
[docs] def setup_schedule(self):
try:
self._store = self._open_schedule()
# In some cases there may be different errors from a storage
# backend for corrupted files. Example - DBPageNotFoundError
# exception from bsddb. In such case the file will be
# successfully opened but the error will be raised on first key
# retrieving.
self._store.keys()
except Exception as exc:
self._store = self._destroy_open_corrupted_schedule(exc)
for _ in (1, 2):
try:
self._store['entries']
except KeyError:
# new schedule db
try:
self._store['entries'] = {}
except KeyError as exc:
self._store = self._destroy_open_corrupted_schedule(exc)
continue
else:
if '__version__' not in self._store:
warning('DB Reset: Account for new __version__ field')
self._store.clear() # remove schedule at 2.2.2 upgrade.
elif 'tz' not in self._store:
warning('DB Reset: Account for new tz field')
self._store.clear() # remove schedule at 3.0.8 upgrade
elif 'utc_enabled' not in self._store:
warning('DB Reset: Account for new utc_enabled field')
self._store.clear() # remove schedule at 3.0.9 upgrade
break
tz = self.app.conf.CELERY_TIMEZONE
stored_tz = self._store.get('tz')
if stored_tz is not None and stored_tz != tz:
warning('Reset: Timezone changed from %r to %r', stored_tz, tz)
self._store.clear() # Timezone changed, reset db!
utc = self.app.conf.CELERY_ENABLE_UTC
stored_utc = self._store.get('utc_enabled')
if stored_utc is not None and stored_utc != utc:
choices = {True: 'enabled', False: 'disabled'}
warning('Reset: UTC changed from %s to %s',
choices[stored_utc], choices[utc])
self._store.clear() # UTC setting changed, reset db!
entries = self._store.setdefault('entries', {})
self.merge_inplace(self.app.conf.CELERYBEAT_SCHEDULE)
self.install_default_entries(self.schedule)
self._store.update(__version__=__version__, tz=tz, utc_enabled=utc)
self.sync()
debug('Current schedule:\n' + '\n'.join(
repr(entry) for entry in values(entries)))
schedule = property(get_schedule, set_schedule)
@property
def info(self):
return ' . db -> {self.schedule_filename}'.format(self=self)
[docs]class Service(object):
scheduler_cls = PersistentScheduler
def __init__(self, app, max_interval=None, schedule_filename=None,
scheduler_cls=None):
self.app = app
self.max_interval = (max_interval or
app.conf.CELERYBEAT_MAX_LOOP_INTERVAL)
self.scheduler_cls = scheduler_cls or self.scheduler_cls
self.schedule_filename = (
schedule_filename or app.conf.CELERYBEAT_SCHEDULE_FILENAME)
self._is_shutdown = Event()
self._is_stopped = Event()
def __reduce__(self):
return self.__class__, (self.max_interval, self.schedule_filename,
self.scheduler_cls, self.app)
[docs] def start(self, embedded_process=False, drift=-0.010):
info('beat: Starting...')
debug('beat: Ticking with max interval->%s',
humanize_seconds(self.scheduler.max_interval))
signals.beat_init.send(sender=self)
if embedded_process:
signals.beat_embedded_init.send(sender=self)
platforms.set_process_title('celery beat')
try:
while not self._is_shutdown.is_set():
interval = self.scheduler.tick()
interval = interval + drift if interval else interval
if interval and interval > 0:
debug('beat: Waking up %s.',
humanize_seconds(interval, prefix='in '))
time.sleep(interval)
if self.scheduler.should_sync():
self.scheduler._do_sync()
except (KeyboardInterrupt, SystemExit):
self._is_shutdown.set()
finally:
self.sync()
[docs] def stop(self, wait=False):
info('beat: Shutting down...')
self._is_shutdown.set()
wait and self._is_stopped.wait() # block until shutdown done.
[docs] def get_scheduler(self, lazy=False):
filename = self.schedule_filename
scheduler = instantiate(self.scheduler_cls,
app=self.app,
schedule_filename=filename,
max_interval=self.max_interval,
lazy=lazy)
return scheduler
@cached_property
class _Threaded(Thread):
"""Embedded task scheduler using threading."""
def __init__(self, app, **kwargs):
super(_Threaded, self).__init__()
self.app = app
self.service = Service(app, **kwargs)
self.daemon = True
self.name = 'Beat'
def run(self):
self.app.set_current()
self.service.start()
def stop(self):
self.service.stop(wait=True)
try:
ensure_multiprocessing()
except NotImplementedError: # pragma: no cover
_Process = None
else:
class _Process(Process): # noqa
def __init__(self, app, **kwargs):
super(_Process, self).__init__()
self.app = app
self.service = Service(app, **kwargs)
self.name = 'Beat'
def run(self):
reset_signals(full=False)
platforms.close_open_fds([
sys.__stdin__, sys.__stdout__, sys.__stderr__,
] + list(iter_open_logger_fds()))
self.app.set_default()
self.app.set_current()
self.service.start(embedded_process=True)
def stop(self):
self.service.stop()
self.terminate()
[docs]def EmbeddedService(app, max_interval=None, **kwargs):
"""Return embedded clock service.
:keyword thread: Run threaded instead of as a separate process.
Uses :mod:`multiprocessing` by default, if available.
"""
if kwargs.pop('thread', False) or _Process is None:
# Need short max interval to be able to stop thread
# in reasonable time.
return _Threaded(app, max_interval=1, **kwargs)
return _Process(app, max_interval=max_interval, **kwargs)
