Question

我想将async/await语法与Twisted Deferred.addCallback方法一起使用。但正如文档中所述，addCallback回调是同步调用的。我已经看到inlineCallbacks装饰器用于此目的，但我更喜欢使用async/await语法（如果它甚至可能，或者有意义）。

我从pika documentation获取了原始代码，但我没有尝试将其迁移到async / await语法：

import pika
from pika import exceptions
from pika.adapters import twisted_connection
from twisted.internet import defer, reactor, protocol, task


async def run_async(connection):
    channel = await connection.channel()
    exchange = await channel.exchange_declare(exchange='topic_link',type='topic')
    queue = await channel.queue_declare(queue='hello', auto_delete=False, exclusive=False)
    await channel.queue_bind(exchange='topic_link', queue='hello', routing_key='hello.world')
    await channel.basic_qos(prefetch_count=1)
    queue_object, consumer_tag = await channel.basic_consume(queue='hello', no_ack=False)
    l = task.LoopingCall(read_async, queue_object)
    l.start(0.01)


async def read_async(queue_object):
    ch,method,properties,body = await queue_object.get()
    if body:
        print(body)
    await ch.basic_ack(delivery_tag=method.delivery_tag)


parameters = pika.ConnectionParameters()
cc = protocol.ClientCreator(reactor, twisted_connection.TwistedProtocolConnection, parameters)
d = cc.connectTCP('rabbitmq', 5672)
d.addCallback(lambda protocol: protocol.ready)
d.addCallback(run_async)
reactor.run()

这显然不起作用，因为没有人等待run_async功能。

Answer 1

正如 notorious.no 和Twisted文档所指出的，ensureDeferred是要走的路。但是，你必须包装回调结果而不是回调本身，这对我来说并不清楚。

最终看起来如此：

def ensure_deferred(f):
    @functools.wraps(f)
    def wrapper(*args, **kwargs):
        result = f(*args, **kwargs)
        return defer.ensureDeferred(result)
    return wrapper


@ensure_deferred
async def run(connection):
    channel = await connection.channel()
    exchange = await channel.exchange_declare(exchange='topic_link', type='topic')
    queue = await channel.queue_declare(queue='hello', auto_delete=False, exclusive=False)
    await channel.queue_bind(exchange='topic_link', queue='hello', routing_key='hello.world')
    await channel.basic_qos(prefetch_count=1)
    queue_object, consumer_tag = await channel.basic_consume(queue='hello', no_ack=False)
    l = task.LoopingCall(read, queue_object)
    l.start(0.01)


@ensure_deferred
async def read(queue_object):
    ch, method, properties, body = await queue_object.get()
    if body:
        print(body)
    await ch.basic_ack(delivery_tag=method.delivery_tag)


parameters = pika.ConnectionParameters()
cc = protocol.ClientCreator(reactor, twisted_connection.TwistedProtocolConnection, parameters)
d = cc.connectTCP('rabbitmq', 5672)
d.addCallback(lambda protocol: protocol.ready)
d.addCallback(run)
reactor.run()

感谢。

使用带有Twisted回调的async / await语法

1 个答案: