This document describes the current stable version of Celery (5.6). For development docs, go here.

# Source code for celery.concurrency.eventlet

    """Eventlet execution pool."""
    import sys
    from time import monotonic

    from greenlet import GreenletExit
    from kombu.asynchronous import timer as _timer

    from celery import signals

    from . import base

    __all__ = ('TaskPool',)

    W_RACE = """\
    Celery module with %s imported before eventlet patched\
    """
    RACE_MODS = ('billiard.', 'celery.', 'kombu.')

    #: Warn if we couldn't patch early enough,
    #: and thread/socket depending celery modules have already been loaded.
    for mod in (mod for mod in sys.modules if mod.startswith(RACE_MODS)):
        for side in ('thread', 'threading', 'socket'):  # pragma: no cover
            if getattr(mod, side, None):
                import warnings
                warnings.warn(RuntimeWarning(W_RACE % side))

    def apply_target(target, args=(), kwargs=None, callback=None,
                     accept_callback=None, getpid=None):
        kwargs = {} if not kwargs else kwargs
        return base.apply_target(target, args, kwargs, callback, accept_callback,
                                 pid=getpid())

    class Timer(_timer.Timer):
        """Eventlet Timer."""

        def __init__(self, *args, **kwargs):
            from eventlet.greenthread import spawn_after
            from greenlet import GreenletExit
            super().__init__(*args, **kwargs)

            self.GreenletExit = GreenletExit
            self._spawn_after = spawn_after
            self._queue = set()

        def _enter(self, eta, priority, entry, **kwargs):
            secs = max(eta - monotonic(), 0)
            g = self._spawn_after(secs, entry)
            self._queue.add(g)
            g.link(self._entry_exit, entry)
            g.entry = entry
            g.eta = eta
            g.priority = priority
            g.canceled = False
            return g

        def _entry_exit(self, g, entry):
            try:
                try:
                    g.wait()
                except self.GreenletExit:
                    entry.cancel()
                    g.canceled = True
            finally:
                self._queue.discard(g)

        def clear(self):
            queue = self._queue
            while queue:
                try:
                    queue.pop().cancel()
                except (KeyError, self.GreenletExit):
                    pass

        def cancel(self, tref):
            try:
                tref.cancel()
            except self.GreenletExit:
                pass

        @property
        def queue(self):
            return self._queue

    class TaskPool(base.BasePool):
        """Eventlet Task Pool."""

        Timer = Timer

        signal_safe = False
        is_green = True
        task_join_will_block = False
        _pool = None
        _pool_map = None
        _quick_put = None

        def __init__(self, *args, **kwargs):
            from eventlet import greenthread
            from eventlet.greenpool import GreenPool
            self.Pool = GreenPool
            self.getcurrent = greenthread.getcurrent
            self.getpid = lambda: id(greenthread.getcurrent())
            self.spawn_n = greenthread.spawn_n

            super().__init__(*args, **kwargs)

        def on_start(self):
            self._pool = self.Pool(self.limit)
            self._pool_map = {}
            signals.eventlet_pool_started.send(sender=self)
            self._quick_put = self._pool.spawn
            self._quick_apply_sig = signals.eventlet_pool_apply.send

        def on_stop(self):
            signals.eventlet_pool_preshutdown.send(sender=self)
            if self._pool is not None:
                self._pool.waitall()
            signals.eventlet_pool_postshutdown.send(sender=self)

        def on_apply(self, target, args=None, kwargs=None, callback=None,
                     accept_callback=None, **_):
            target = TaskPool._make_killable_target(target)
            self._quick_apply_sig(sender=self, target=target, args=args, kwargs=kwargs,)
            greenlet = self._quick_put(
                apply_target,
                target, args,
                kwargs,
                callback,
                accept_callback,
                self.getpid
            )
            self._add_to_pool_map(id(greenlet), greenlet)

        def grow(self, n=1):
            limit = self.limit + n
            self._pool.resize(limit)
            self.limit = limit

        def shrink(self, n=1):
            limit = self.limit - n
            self._pool.resize(limit)
            self.limit = limit

        def terminate_job(self, pid, signal=None):
            if pid in self._pool_map.keys():
                greenlet = self._pool_map[pid]
                greenlet.kill()
                greenlet.wait()

        def _get_info(self):
            info = super()._get_info()
            info.update({
                'max-concurrency': self.limit,
                'free-threads': self._pool.free(),
                'running-threads': self._pool.running(),
            })
            return info

        @staticmethod
        def _make_killable_target(target):
            def killable_target(*args, **kwargs):
                try:
                    return target(*args, **kwargs)
                except GreenletExit:
                    return (False, None, None)
            return killable_target

        def _add_to_pool_map(self, pid, greenlet):
            self._pool_map[pid] = greenlet
            greenlet.link(
                TaskPool._cleanup_after_job_finish,
                self._pool_map,
                pid
            )

        @staticmethod
        def _cleanup_after_job_finish(greenlet, pool_map, pid):
            del pool_map[pid]