使用扭曲回调的异步/等待语法
问题描述:
我想用Twisted Deferred.addCallback方法使用async/await
语法。但正如文档中所述,addCallback
回调被称为同步。我已经看到inlineCallbacks用于此目的的装饰器,但我更喜欢使用async/await
语法(如果它甚至可能或有意义)。使用扭曲回调的异步/等待语法
我从pika documentation拿起原来的代码,但我没有运气试图迁移至异步/ 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()
这显然是行不通的,因为没有人等待run_async
功能。
答
正如notorious.no和Twisted文档指出的,ensureDeferred
是要走的路。不过,你必须包装回调结果,而不是回调本身,这是我不明白。
这是它的外观,最终:
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。
['ensureDeferred'](https://twistedmatrix.com/documents/current/core/howto/defer-intro.html#coroutines-with-async-await)就是你想要的 –
@ notorious.no我已经尝试用'defer.ensureDeferred'封装'cc.connectTCP('rabbitmq',5672)',但它没有帮助。那是你的意思吗?谢谢。 – user1527491
@ notorious.no明白了。我必须用ensureDeferred包装回调本身。我正在封装回调的结果,这显然没有成功。谢谢。 – user1527491