使用Google Cloud Pub/Sub取消订阅时遇指定RuntimeError错误

你遇到的错误如下：

self = <google.cloud.pubsub_v1.SubscriberClient object at 0x000002069A31D820>

    def __enter__(self) -> "Client":
        if self._closed:
>           raise RuntimeError("Closed subscriber cannot be used as context manager.")
E           RuntimeError: Closed subscriber cannot be used as context manager.

venv\lib\site-packages\google\cloud\pubsub_v1\subscriber\client.py:285: RuntimeError

问题核心是你复用的self.subscriber客户端已处于关闭状态，却仍在with语句中使用。with语法会在代码块执行完毕后自动调用客户端的close()方法，若后续再次使用这个已关闭的客户端进入with块，就会触发上述错误。

解决方案1：每次操作创建新客户端实例 #

如果不需要复用客户端，建议在调用取消订阅方法时每次创建新的SubscriberClient，配合with自动管理资源：

from google.cloud import pubsub_v1

def unsubscribe(self, subscription_id):
    # 每次调用创建新的客户端实例
    subscriber = pubsub_v1.SubscriberClient()
    subscription_path = subscriber.subscription_path(self.project_id, subscription_id)

    with subscriber:
        subscriber.delete_subscription(request={"subscription": subscription_path})

    return True

解决方案2：复用客户端并手动管理生命周期 #

如果需要复用self.subscriber，则不要用with语句包裹，手动控制客户端的生命周期：

def unsubscribe(self, subscription_id):
    subscriber = self.subscriber
    # 检查客户端是否已关闭，若关闭则重新初始化
    if subscriber._closed:
        subscriber = pubsub_v1.SubscriberClient()
        self.subscriber = subscriber

    subscription_path = subscriber.subscription_path(self.project_id, subscription_id)
    subscriber.delete_subscription(request={"subscription": subscription_path})
    
    # 若后续不再使用该客户端，可手动执行关闭
    # subscriber.close()
    return True

内容的提问来源于stack exchange，提问作者Dshiz