Class TaskSemaphore

awscli/s3transfer/utils.py:617–651

class TaskSemaphore:
    def __init__(self, count):
        """A semaphore for the purpose of limiting the number of tasks

        :param count: The size of semaphore
        """
        self._semaphore = threading.Semaphore(count)

    def acquire(self, tag, blocking=True):
        """Acquire the semaphore

        :param tag: A tag identifying what is acquiring the semaphore. Note
            that this is not really needed to directly use this class but is
            needed for API compatibility with the SlidingWindowSemaphore
            implementation.
        :param block: If True, block until it can be acquired. If False,
            do not block and raise an exception if cannot be acquired.

        :returns: A token (can be None) to use when releasing the semaphore
        """
        logger.debug("Acquiring %s", tag)
        if not self._semaphore.acquire(blocking):
            raise NoResourcesAvailable(f"Cannot acquire tag '{tag}'")

    def release(self, tag, acquire_token):
        """Release the semaphore

        :param tag: A tag identifying what is releasing the semaphore
        :param acquire_token:  The token returned from when the semaphore was
            acquired. Note that this is not really needed to directly use this
            class but is needed for API compatibility with the
            SlidingWindowSemaphore implementation.
        """
        logger.debug(f"Releasing acquire {tag}/{acquire_token}")
        self._semaphore.release()


class SlidingWindowSemaphore(TaskSemaphore):