This document describes the current stable version of Kombu (4.0). For development docs, go here.

Semaphores - kombu.async.semaphore

Semaphores and concurrency primitives.

class kombu.async.semaphore.DummyLock

Pretending to be a lock.

class kombu.async.semaphore.LaxBoundedSemaphore(value)

Asynchronous Bounded Semaphore.

Lax means that the value will stay within the specified range even if released more times than it was acquired.

Example

>>> from future import print_statement as printf
# ^ ignore: just fooling stupid pyflakes

>>> x = LaxBoundedSemaphore(2)

>>> x.acquire(printf, 'HELLO 1')
HELLO 1

>>> x.acquire(printf, 'HELLO 2')
HELLO 2

>>> x.acquire(printf, 'HELLO 3')
>>> x._waiters   # private, do not access directly
[print, ('HELLO 3',)]

>>> x.release()
HELLO 3

acquire(callback, *partial_args, **partial_kwargs)

Acquire semaphore.

This will immediately apply callback if the resource is available, otherwise the callback is suspended until the semaphore is released.

Parameters:

• callback (Callable) – The callback to apply.
• *partial_args (Any) – partial arguments to callback.

clear()

Reset the semaphore, which also wipes out any waiting callbacks.

grow(n=1)

Change the size of the semaphore to accept more users.

release()

Release semaphore.

Note

If there are any waiters this will apply the first waiter that is waiting for the resource (FIFO order).

shrink(n=1)

Change the size of the semaphore to accept less users.