Warning: This document is for the development version of Dramatiq.

Source code for dramatiq.rate_limits.barrier

# This file is a part of Dramatiq.
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# Copyright (C) 2017,2018 CLEARTYPE SRL <bogdan@cleartype.io>
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# Dramatiq is free software; you can redistribute it and/or modify it
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[docs]class Barrier: """A distributed barrier. Examples: >>> from dramatiq.rate_limits import Barrier >>> from dramatiq.rate_limits.backends import RedisBackend >>> backend = RedisBackend() >>> barrier = Barrier(backend, "some-barrier", ttl=30_000) >>> created = barrier.create(parties=3) >>> barrier.wait(block=False) False >>> barrier.wait(block=False) False >>> barrier.wait(block=False) True Parameters: backend(BarrierBackend): The barrier backend to use. key(str): The key for the barrier. ttl(int): The TTL for the barrier key, in milliseconds. """ def __init__(self, backend, key, *, ttl=900000): self.backend = backend self.key = key self.key_events = key + "@events" self.ttl = ttl
[docs] def create(self, parties): """Create the barrier for the given number of parties. Parameters: parties(int): The number of parties to wait for. Returns: bool: Whether or not the new barrier was successfully created. """ assert parties > 0, "parties must be a positive integer." return self.backend.add(self.key, parties, self.ttl)
[docs] def wait(self, *, block=True, timeout=None): """Signal that a party has reached the barrier. Warning: Barrier blocking is currently only supported by the stub and Redis backends. Warning: Re-using keys between blocking calls may lead to undefined behaviour. Make sure your barrier keys are always unique (use a UUID). Parameters: block(bool): Whether or not to block while waiting for the other parties. timeout(int): The maximum number of milliseconds to wait for the barrier to be cleared. Returns: bool: Whether or not the barrier has been reached by all parties. """ cleared = not self.backend.decr(self.key, 1, 1, self.ttl) if cleared: self.backend.wait_notify(self.key_events, self.ttl) return True if block: return self.backend.wait(self.key_events, timeout) return False