Google Cloud PubSub在异步请求中侦听消息时抛出504 Deadline Exceeded错误

我有一个订阅PubSub主题并使用异步请求的服务。闲置10分钟且未收到任何消息后，PubSub抛出504超过期限错误。

总是在大约10分钟后发生错误。我发现的每个类似问题都与同步请求有关，而不与我使用的异步请求有关。

错误信息：

INFO:google.cloud.pubsub_v1.subscriber._protocol.streaming_pull_manager:Observed non-terminating stream error 504 Deadline Exceeded                                                                                                           
INFO:google.cloud.pubsub_v1.subscriber._protocol.streaming_pull_manager:Observed recoverable stream error 504 Deadline Exceeded                                                                                                                 
INFO:google.api_core.bidi:Re-established stream                                                                         
INFO:google.cloud.pubsub_v1.subscriber._protocol.streaming_pull_manager:Observed non-terminating stream error 504 Deadline Exceeded                                                                                                             
INFO:google.cloud.pubsub_v1.subscriber._protocol.streaming_pull_manager:Observed recoverable stream error 504 Deadline Exceeded

订户类别：

from google.cloud import pubsub_v1
class Subscriber():

    def __init__(self):
        self.subscriber = pubsub_v1.SubscriberClient()
        self.project_id = "my-project-id"
        self.subscription_id = "SUBSCRIPTION_MAIL_RECIEVE"
        self.subscription_path = self.subscriber.subscription_path(self.project_id,
                                                                   self.subscription_id)

    def subscribe(self, callback):
        """
        Parameters:
            callback (callable): function to be called for incoming messages on given topic
        """
        streaming_pull_future = self.subscriber.subscribe(self.subscription_path,
                                                          callback=callback)
        return streaming_pull_future

收听消息：

subscriber = Subscriber()
pull_future = subscriber.subscribe(my_callback_function(message))

with subscriber.subscriber:
        try:
            print("Waiting for messages")
            pull_future.result()
        except TimeoutError:
            pull_future.cancel()