deb-python-eventlet/eventlet/coros.py

import collections
import traceback
import warnings

import eventlet
from eventlet import event as _event
from eventlet import hubs
from eventlet import greenthread
from eventlet import semaphore as semaphoremod

class NOT_USED:
    def __repr__(self):
        return 'NOT_USED'

NOT_USED = NOT_USED()

def Event(*a, **kw):
    warnings.warn("The Event class has been moved to the event module! "
                   "Please construct event.Event objects instead.",
                   DeprecationWarning, stacklevel=2)
    return _event.Event(*a, **kw)


def event(*a, **kw):
    warnings.warn("The event class has been capitalized and moved!  Please "
        "construct event.Event objects instead.",
        DeprecationWarning, stacklevel=2)
    return _event.Event(*a, **kw)


def Semaphore(count):
    warnings.warn("The Semaphore class has moved!  Please "
        "use semaphore.Semaphore instead.",
        DeprecationWarning, stacklevel=2)
    return semaphoremod.Semaphore(count)

def BoundedSemaphore(count):
    warnings.warn("The BoundedSemaphore class has moved!  Please "
        "use semaphore.BoundedSemaphore instead.",
        DeprecationWarning, stacklevel=2)
    return semaphoremod.BoundedSemaphore(count)

def semaphore(count=0, limit=None):
    warnings.warn("coros.semaphore is deprecated.  Please use either "
        "semaphore.Semaphore or semaphore.BoundedSemaphore instead.",
        DeprecationWarning, stacklevel=2)
    if limit is None:
        return Semaphore(count)
    else:
        return BoundedSemaphore(count)


class metaphore(object):
    """This is sort of an inverse semaphore: a counter that starts at 0 and
    waits only if nonzero. It's used to implement a "wait for all" scenario.

    >>> from eventlet import api, coros
    >>> count = coros.metaphore()
    >>> count.wait()
    >>> def decrementer(count, id):
    ...     print "%s decrementing" % id
    ...     count.dec()
    ...
    >>> _ = eventlet.spawn(decrementer, count, 'A')
    >>> _ = eventlet.spawn(decrementer, count, 'B')
    >>> count.inc(2)
    >>> count.wait()
    A decrementing
    B decrementing
    """
    def __init__(self):
        self.counter = 0
        self.event = _event.Event()
        # send() right away, else we'd wait on the default 0 count!
        self.event.send()

    def inc(self, by=1):
        """Increment our counter. If this transitions the counter from zero to
        nonzero, make any subsequent :meth:`wait` call wait.
        """
        assert by > 0
        self.counter += by
        if self.counter == by:
            # If we just incremented self.counter by 'by', and the new count
            # equals 'by', then the old value of self.counter was 0.
            # Transitioning from 0 to a nonzero value means wait() must
            # actually wait.
            self.event.reset()

    def dec(self, by=1):
        """Decrement our counter. If this transitions the counter from nonzero
        to zero, a current or subsequent wait() call need no longer wait.
        """
        assert by > 0
        self.counter -= by
        if self.counter <= 0:
            # Don't leave self.counter < 0, that will screw things up in
            # future calls.
            self.counter = 0
            # Transitioning from nonzero to 0 means wait() need no longer wait.
            self.event.send()

    def wait(self):
        """Suspend the caller only if our count is nonzero. In that case,
        resume the caller once the count decrements to zero again.
        """
        self.event.wait()

def execute(func, *args, **kw):
    """ Executes an operation asynchronously in a new coroutine, returning
    an event to retrieve the return value.

    This has the same api as the :meth:`eventlet.coros.CoroutinePool.execute`
    method; the only difference is that this one creates a new coroutine
    instead of drawing from a pool.

    >>> from eventlet import coros
    >>> evt = coros.execute(lambda a: ('foo', a), 1)
    >>> evt.wait()
    ('foo', 1)
    """
    warnings.warn("Coros.execute is deprecated.  Please use eventlet.spawn "
        "instead.", DeprecationWarning, stacklevel=2)
    return greenthread.spawn(func, *args, **kw)


def CoroutinePool(*args, **kwargs):
    warnings.warn("CoroutinePool is deprecated.  Please use "
        "eventlet.GreenPool instead.", DeprecationWarning, stacklevel=2)
    from eventlet.pool import Pool
    return Pool(*args, **kwargs)


class Queue(object):

    def __init__(self):
        warnings.warn("coros.Queue is deprecated.  Please use "
            "eventlet.queue.Queue instead.",
            DeprecationWarning, stacklevel=2)
        self.items = collections.deque()
        self._waiters = set()

    def __nonzero__(self):
        return len(self.items)>0

    def __len__(self):
        return len(self.items)

    def __repr__(self):
        params = (self.__class__.__name__, hex(id(self)),
                  len(self.items), len(self._waiters))
        return '<%s at %s items[%d] _waiters[%s]>' % params

    def send(self, result=None, exc=None):
        if exc is not None and not isinstance(exc, tuple):
            exc = (exc, )
        self.items.append((result, exc))
        if self._waiters:
            hubs.get_hub().schedule_call_global(0, self._do_send)

    def send_exception(self, *args):
        # the arguments are the same as for greenlet.throw
        return self.send(exc=args)

    def _do_send(self):
        if self._waiters and self.items:
            waiter = self._waiters.pop()
            result, exc = self.items.popleft()
            waiter.switch((result, exc))

    def wait(self):
        if self.items:
            result, exc = self.items.popleft()
            if exc is None:
                return result
            else:
                eventlet.getcurrent().throw(*exc)
        else:
            self._waiters.add(eventlet.getcurrent())
            try:
                result, exc = hubs.get_hub().switch()
                if exc is None:
                    return result
                else:
                    eventlet.getcurrent().throw(*exc)
            finally:
                self._waiters.discard(eventlet.getcurrent())

    def ready(self):
        return len(self.items) > 0

    def full(self):
        # for consistency with Channel
        return False

    def waiting(self):
        return len(self._waiters)

    def __iter__(self):
        return self

    def next(self):
        return self.wait()


class Channel(object):

    def __init__(self, max_size=0):
        warnings.warn("coros.Channel is deprecated.  Please use "
            "eventlet.queue.Queue(0) instead.",
            DeprecationWarning, stacklevel=2)
        self.max_size = max_size
        self.items = collections.deque()
        self._waiters = set()
        self._senders = set()

    def __nonzero__(self):
        return len(self.items)>0

    def __len__(self):
        return len(self.items)

    def __repr__(self):
        params = (self.__class__.__name__, hex(id(self)),
                  self.max_size, len(self.items),
                  len(self._waiters), len(self._senders))
        return '<%s at %s max=%s items[%d] _w[%s] _s[%s]>' % params

    def send(self, result=None, exc=None):
        if exc is not None and not isinstance(exc, tuple):
            exc = (exc, )
        if eventlet.getcurrent() is hubs.get_hub().greenlet:
            self.items.append((result, exc))
            if self._waiters:
                hubs.get_hub().schedule_call_global(0, self._do_switch)
        else:
            self.items.append((result, exc))
            # note that send() does not work well with timeouts. if your timeout fires
            # after this point, the item will remain in the queue
            if self._waiters:
                hubs.get_hub().schedule_call_global(0, self._do_switch)
            if len(self.items) > self.max_size:
                self._senders.add(eventlet.getcurrent())
                try:
                    hubs.get_hub().switch()
                finally:
                    self._senders.discard(eventlet.getcurrent())

    def send_exception(self, *args):
        # the arguments are the same as for greenlet.throw
        return self.send(exc=args)

    def _do_switch(self):
        while True:
            if self._waiters and self.items:
                waiter = self._waiters.pop()
                result, exc = self.items.popleft()
                try:
                    waiter.switch((result, exc))
                except:
                    traceback.print_exc()
            elif self._senders and len(self.items) <= self.max_size:
                sender = self._senders.pop()
                try:
                    sender.switch()
                except:
                    traceback.print_exc()
            else:
                break

    def wait(self):
        if self.items:
            result, exc = self.items.popleft()
            if len(self.items) <= self.max_size:
                hubs.get_hub().schedule_call_global(0, self._do_switch)
            if exc is None:
                return result
            else:
                eventlet.getcurrent().throw(*exc)
        else:
            if self._senders:
                hubs.get_hub().schedule_call_global(0, self._do_switch)
            self._waiters.add(eventlet.getcurrent())
            try:
                result, exc = hubs.get_hub().switch()
                if exc is None:
                    return result
                else:
                    eventlet.getcurrent().throw(*exc)
            finally:
                self._waiters.discard(eventlet.getcurrent())

    def ready(self):
        return len(self.items) > 0

    def full(self):
        return len(self.items) >= self.max_size

    def waiting(self):
        return max(0, len(self._waiters) - len(self.items))


def queue(max_size=None):
    if max_size is None:
        return Queue()
    else:
        return Channel(max_size)


class Actor(object):
    """ A free-running coroutine that accepts and processes messages.

    Kind of the equivalent of an Erlang process, really.  It processes
    a queue of messages in the order that they were sent.  You must
    subclass this and implement your own version of :meth:`received`.

    The actor's reference count will never drop to zero while the
    coroutine exists; if you lose all references to the actor object
    it will never be freed.
    """
    def __init__(self, concurrency = 1):
        """ Constructs an Actor, kicking off a new coroutine to process the messages.

        The concurrency argument specifies how many messages the actor will try
        to process concurrently.  If it is 1, the actor will process messages
        serially.
        """
        warnings.warn("We're phasing out the Actor class, so as to get rid of"
                   "the coros module.  If you use Actor, please speak up on "
                   "eventletdev@lists.secondlife.com, and we'll come up with a "
                   "transition plan.  If no one speaks up, we'll remove Actor "
                   "in a future release of Eventlet.",
                   DeprecationWarning, stacklevel=2)

        self._mailbox = collections.deque()
        self._event = _event.Event()
        self._killer = eventlet.spawn(self.run_forever)
        from eventlet import greenpool
        self._pool = greenpool.GreenPool(concurrency)

    def run_forever(self):
        """ Loops forever, continually checking the mailbox. """
        while True:
            if not self._mailbox:
                self._event.wait()
                self._event = _event.Event()
            else:
                # leave the message in the mailbox until after it's
                # been processed so the event doesn't get triggered
                # while in the received method
                self._pool.spawn_n(
                    self.received, self._mailbox[0])
                self._mailbox.popleft()

    def cast(self, message):
        """ Send a message to the actor.

        If the actor is busy, the message will be enqueued for later
        consumption.  There is no return value.

        >>> a = Actor()
        >>> a.received = lambda msg: msg
        >>> a.cast("hello")
        """
        self._mailbox.append(message)
        # if this is the only message, the coro could be waiting
        if len(self._mailbox) == 1:
            self._event.send()

    def received(self, message):
        """ Called to process each incoming message.

        The default implementation just raises an exception, so
        replace it with something useful!

        >>> class Greeter(Actor):
        ...     def received(self, (message, evt) ):
        ...         print "received", message
        ...         if evt: evt.send()
        ...
        >>> a = Greeter()

        This example uses Events to synchronize between the actor and the main
        coroutine in a predictable manner, but this kinda defeats the point of
        the :class:`Actor`, so don't do it in a real application.

        >>> from eventlet.event import Event
        >>> evt = Event()
        >>> a.cast( ("message 1", evt) )
        >>> evt.wait()  # force it to run at this exact moment
        received message 1
        >>> evt.reset()
        >>> a.cast( ("message 2", None) )
        >>> a.cast( ("message 3", evt) )
        >>> evt.wait()
        received message 2
        received message 3

        >>> eventlet.kill(a._killer)   # test cleanup
        """
        raise NotImplementedError()