This document describes the current stable version of Kombu (5.3). For development docs, go here.
Source code for kombu.asynchronous.hub
"""Event loop implementation."""
from __future__ import annotations
import errno
import threading
from contextlib import contextmanager
from copy import copy
from queue import Empty
from time import sleep
from types import GeneratorType as generator
from vine import Thenable, promise
from kombu.log import get_logger
from kombu.utils.compat import fileno
from kombu.utils.eventio import ERR, READ, WRITE, poll
from kombu.utils.objects import cached_property
from .timer import Timer
__all__ = ('Hub', 'get_event_loop', 'set_event_loop')
logger = get_logger(__name__)
_current_loop: Hub | None = None
W_UNKNOWN_EVENT = """\
Received unknown event %r for fd %r, please contact support!\
"""
class Stop(BaseException):
"""Stops the event loop."""
def _raise_stop_error():
raise Stop()
@contextmanager
def _dummy_context(*args, **kwargs):
yield
[docs]
def get_event_loop() -> Hub | None:
"""Get current event loop object."""
return _current_loop
[docs]
def set_event_loop(loop: Hub | None) -> Hub | None:
"""Set the current event loop object."""
global _current_loop
_current_loop = loop
return loop
[docs]
class Hub:
"""Event loop object.
Arguments:
---------
timer (kombu.asynchronous.Timer): Specify custom timer instance.
"""
#: 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 exiting,
#: applied with the hub instance as sole argument.
on_close = None
def __init__(self, timer=None):
self.timer = timer if timer is not None else Timer()
self.readers = {}
self.writers = {}
self.on_tick = set()
self.on_close = set()
self._ready = set()
self._ready_lock = threading.Lock()
self._running = False
self._loop = None
# The eventloop (in celery.worker.loops)
# will merge fds in this set and then instead of calling
# the callback for each ready fd it will call the
# :attr:`consolidate_callback` with the list of ready_fds
# as an argument. This API is internal and is only
# used by the multiprocessing pool to find inqueues
# that are ready to write.
self.consolidate = set()
self.consolidate_callback = None
self.propagate_errors = ()
self._create_poller()
@property
def poller(self):
if not self._poller:
self._create_poller()
return self._poller
@poller.setter
def poller(self, value):
self._poller = value
def _create_poller(self):
self._poller = poll()
self._register_fd = self._poller.register
self._unregister_fd = self._poller.unregister
def _close_poller(self):
if self._poller is not None:
self._poller.close()
self._poller = None
self._register_fd = None
self._unregister_fd = None
def __repr__(self):
return '<Hub@{:#x}: R:{} W:{}>'.format(
id(self), len(self.readers), len(self.writers),
)
[docs]
def fire_timers(self, min_delay=1, max_delay=10, max_timers=10,
propagate=()):
timer = self.timer
delay = None
if timer and timer._queue:
for i in range(max_timers):
delay, entry = next(self.scheduler)
if entry is None:
break
try:
entry()
except propagate:
raise
except (MemoryError, AssertionError):
raise
except OSError as exc:
if exc.errno == errno.ENOMEM:
raise
logger.error('Error in timer: %r', exc, exc_info=1)
except Exception as exc:
logger.error('Error in timer: %r', exc, exc_info=1)
return min(delay or min_delay, max_delay)
def _remove_from_loop(self, fd):
try:
self._unregister(fd)
finally:
self._discard(fd)
[docs]
def add(self, fd, callback, flags, args=(), consolidate=False):
fd = fileno(fd)
try:
self.poller.register(fd, flags)
except ValueError:
self._remove_from_loop(fd)
raise
else:
dest = self.readers if flags & READ else self.writers
if consolidate:
self.consolidate.add(fd)
dest[fd] = None
else:
dest[fd] = callback, args
[docs]
def run_forever(self):
self._running = True
try:
while 1:
try:
self.run_once()
except Stop:
break
finally:
self._running = False
[docs]
def call_soon(self, callback, *args):
if not isinstance(callback, Thenable):
callback = promise(callback, args)
with self._ready_lock:
self._ready.add(callback)
return callback
[docs]
def call_later(self, delay, callback, *args):
return self.timer.call_after(delay, callback, args)
[docs]
def call_repeatedly(self, delay, callback, *args):
return self.timer.call_repeatedly(delay, callback, args)
[docs]
def remove_reader(self, fd):
writable = fd in self.writers
on_write = self.writers.get(fd)
try:
self._remove_from_loop(fd)
finally:
if writable:
cb, args = on_write
self.add(fd, cb, WRITE, args)
[docs]
def remove_writer(self, fd):
readable = fd in self.readers
on_read = self.readers.get(fd)
try:
self._remove_from_loop(fd)
finally:
if readable:
cb, args = on_read
self.add(fd, cb, READ | ERR, args)
def _unregister(self, fd):
try:
self.poller.unregister(fd)
except (AttributeError, KeyError, OSError):
pass
def _pop_ready(self):
with self._ready_lock:
ready = self._ready
self._ready = set()
return ready
[docs]
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()
self.consolidate.clear()
self._close_poller()
for callback in self.on_close:
callback(self)
# Complete remaining todo before Hub close
# Eg: Acknowledge message
# To avoid infinite loop where one of the callables adds items
# to self._ready (via call_soon or otherwise).
# we create new list with current self._ready
todos = self._pop_ready()
for item in todos:
item()
def _discard(self, fd):
fd = fileno(fd)
self.readers.pop(fd, None)
self.writers.pop(fd, None)
self.consolidate.discard(fd)
[docs]
def on_callback_error(self, callback, exc):
logger.error(
'Callback %r raised exception: %r', callback, exc, exc_info=1,
)
[docs]
def create_loop(self,
generator=generator, sleep=sleep, min=min, next=next,
Empty=Empty, StopIteration=StopIteration,
KeyError=KeyError, READ=READ, WRITE=WRITE, ERR=ERR):
readers, writers = self.readers, self.writers
poll = self.poller.poll
fire_timers = self.fire_timers
hub_remove = self.remove
scheduled = self.timer._queue
consolidate = self.consolidate
consolidate_callback = self.consolidate_callback
propagate = self.propagate_errors
while 1:
todo = self._pop_ready()
for item in todo:
if item:
item()
poll_timeout = fire_timers(propagate=propagate) if scheduled else 1
for tick_callback in copy(self.on_tick):
tick_callback()
# print('[[[HUB]]]: %s' % (self.repr_active(),))
if readers or writers:
to_consolidate = []
try:
events = poll(poll_timeout)
# print('[EVENTS]: %s' % (self.repr_events(events),))
except ValueError: # Issue celery/#882
return
for fd, event in events or ():
general_error = False
if fd in consolidate and \
writers.get(fd) is None:
to_consolidate.append(fd)
continue
cb = cbargs = None
if event & READ:
try:
cb, cbargs = readers[fd]
except KeyError:
self.remove_reader(fd)
continue
elif event & WRITE:
try:
cb, cbargs = writers[fd]
except KeyError:
self.remove_writer(fd)
continue
elif event & ERR:
general_error = True
else:
logger.info(W_UNKNOWN_EVENT, event, fd)
general_error = True
if general_error:
try:
cb, cbargs = (readers.get(fd) or
writers.get(fd))
except TypeError:
pass
if cb is None:
self.remove(fd)
continue
if isinstance(cb, generator):
try:
next(cb)
except OSError as exc:
if exc.errno != errno.EBADF:
raise
hub_remove(fd)
except StopIteration:
pass
except Exception:
hub_remove(fd)
raise
else:
try:
cb(*cbargs)
except Empty:
pass
if to_consolidate:
consolidate_callback(to_consolidate)
else:
# no sockets yet, startup is probably not done.
sleep(min(poll_timeout, 0.1))
yield
[docs]
def repr_events(self, events):
from .debug import repr_events
return repr_events(self, events or [])
@cached_property
def scheduler(self):
return iter(self.timer)
@property
def loop(self):
if self._loop is None:
self._loop = self.create_loop()
return self._loop
