/
hub.py
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/
hub.py
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# -*- coding: utf-8 -*-
"""
celery.worker.hub
~~~~~~~~~~~~~~~~~
Event-loop implementation.
"""
from __future__ import absolute_import
from kombu.utils import cached_property
from kombu.utils import eventio
from kombu.utils.eventio import READ, WRITE, ERR
from celery.five import items, range
from celery.platforms import fileno
from celery.utils.functional import maybe_list
from celery.utils.log import get_logger
from celery.utils.timer2 import Schedule
logger = get_logger(__name__)
def repr_flag(flag):
return '{0}{1}{2}'.format('R' if flag & READ else '',
'W' if flag & WRITE else '',
'!' if flag & ERR else '')
def _rcb(obj):
if obj is None:
return '<missing>'
if isinstance(obj, str):
return obj
return obj.__name__
class BoundedSemaphore(object):
"""Asynchronous Bounded Semaphore.
Bounded means that the value will stay within the specified
range even if it is released more times than it was acquired.
This type is *not thread safe*.
Example:
>>> x = BoundedSemaphore(2)
>>> def callback(i):
... say('HELLO {0!r}'.format(i))
>>> x.acquire(callback, 1)
HELLO 1
>>> x.acquire(callback, 2)
HELLO 2
>>> x.acquire(callback, 3)
>>> x._waiters # private, do not access directly
[(callback, 3)]
>>> x.release()
HELLO 3
"""
def __init__(self, value):
self.initial_value = self.value = value
self._waiting = []
def acquire(self, callback, *partial_args):
"""Acquire semaphore, applying ``callback`` when
the semaphore is ready.
:param callback: The callback to apply.
:param \*partial_args: partial arguments to callback.
"""
if self.value <= 0:
self._waiting.append((callback, partial_args))
return False
else:
self.value = max(self.value - 1, 0)
callback(*partial_args)
return True
def release(self):
"""Release semaphore.
This will apply any waiting callbacks from previous
calls to :meth:`acquire` done when the semaphore was busy.
"""
self.value = min(self.value + 1, self.initial_value)
if self._waiting:
waiter, args = self._waiting.pop()
waiter(*args)
def grow(self, n=1):
"""Change the size of the semaphore to hold more values."""
self.initial_value += n
self.value += n
[self.release() for _ in range(n)]
def shrink(self, n=1):
"""Change the size of the semaphore to hold less values."""
self.initial_value = max(self.initial_value - n, 0)
self.value = max(self.value - n, 0)
def clear(self):
"""Reset the sempahore, including wiping out any waiting callbacks."""
self._waiting[:] = []
self.value = self.initial_value
class Hub(object):
"""Event loop object.
:keyword timer: Specify custom :class:`~celery.utils.timer2.Schedule`.
"""
#: Flag set if reading from an fd will not block.
READ = READ
#: Flag set if writing to an fd will not block.
WRITE = WRITE
#: Flag set on error, and the fd should be read from asap.
ERR = ERR
#: List of callbacks to be called when the loop is initialized,
#: applied with the hub instance as sole argument.
on_init = None
#: List of callbacks to be called when the loop is exiting,
#: applied with the hub instance as sole argument.
on_close = None
#: List of callbacks to be called when a task is received.
#: Takes no arguments.
on_task = None
def __init__(self, timer=None):
self.timer = Schedule() if timer is None else timer
self.readers = {}
self.writers = {}
self.on_init = []
self.on_close = []
self.on_task = []
self.consolidate = set()
self.consolidate_callback = None
def start(self):
"""Called by Hub bootstep at worker startup."""
self.poller = eventio.poll()
def stop(self):
"""Called by Hub bootstep at worker shutdown."""
self.poller.close()
def init(self):
for callback in self.on_init:
callback(self)
def fire_timers(self, min_delay=1, max_delay=10, max_timers=10,
propagate=()):
delay = None
if self.timer._queue:
for i in range(max_timers):
delay, entry = next(self.scheduler)
if entry is None:
break
try:
entry()
except propagate:
raise
except Exception as exc:
logger.error('Error in timer: %r', exc, exc_info=1)
return min(max(delay or 0, min_delay), max_delay)
def _add(self, fd, cb, flags, consolidate=False):
#if flags & WRITE:
# ex = self.writers.get(fd)
# if ex and ex.__name__ == '_write_job':
# assert not ex.gi_frame or ex.gi_frame == -1
self.poller.register(fd, flags)
(self.readers if flags & READ else self.writers)[fileno(fd)] = cb
if consolidate:
self.consolidate.add(fd)
def add(self, fds, callback, flags, consolidate=False):
for fd in maybe_list(fds, None):
try:
self._add(fd, callback, flags, consolidate)
except ValueError:
self._discard(fd)
def remove(self, fd):
fd = fileno(fd)
self._unregister(fd)
self._discard(fd)
def add_reader(self, fds, callback):
return self.add(fds, callback, READ | ERR)
def add_writer(self, fds, callback):
return self.add(fds, callback, WRITE)
def update_readers(self, readers):
[self.add_reader(*x) for x in items(readers)]
def update_writers(self, writers):
[self.add_writer(*x) for x in items(writers)]
def _unregister(self, fd):
try:
self.poller.unregister(fd)
except (KeyError, OSError):
pass
def _discard(self, fd):
fd = fileno(fd)
self.readers.pop(fd, None)
self.writers.pop(fd, None)
self.consolidate.discard(fd)
def close(self, *args):
[self._unregister(fd) for fd in self.readers]
self.readers.clear()
[self._unregister(fd) for fd in self.writers]
self.writers.clear()
for callback in self.on_close:
callback(self)
def _repr_readers(self):
return ['({0}){1}->{2}'.format(fd, _rcb(cb), repr_flag(READ | ERR))
for fd, cb in items(self.readers)]
def _repr_writers(self):
return ['({0}){1}->{2}'.format(fd, _rcb(cb), repr_flag(WRITE))
for fd, cb in items(self.writers)]
def repr_active(self):
return ', '.join(self._repr_readers() + self._repr_writers())
def repr_events(self, events):
return ', '.join(
'{0}->{1}'.format(
_rcb(self._callback_for(fd, fl, '{0!r}(GONE)'.format(fd))),
repr_flag(fl),
)
for fd, fl in events
)
def _callback_for(self, fd, flag, *default):
try:
if flag & READ:
return self.readers[fileno(fd)]
if flag & WRITE:
return self.writers[fileno(fd)]
except KeyError:
if default:
return default[0]
raise
@cached_property
def scheduler(self):
return iter(self.timer)
class DummyLock(object):
"""Pretending to be a lock."""
def __enter__(self):
return self
def __exit__(self, *exc_info):
pass