如何使用python客户端库获取Pubsub中存在的未送达消息(指标api)的数量？

要使用Python客户端库获取Pubsub中存在的未送达消息的数量，可以按照以下步骤进行操作：

导入所需的库和模块：

from google.cloud import pubsub_v1

创建一个Pubsub客户端：

publisher = pubsub_v1.PublisherClient()

指定要查询的主题和订阅：

project_id = "your-project-id"
topic_id = "your-topic-id"
subscription_id = "your-subscription-id"

构建查询未送达消息的请求：

topic_path = publisher.topic_path(project_id, topic_id)
subscription_path = publisher.subscription_path(project_id, subscription_id)

response = publisher.get_topic_subscriptions(request={"topic": topic_path})
subscription_names = response.subscriptions

request = pubsub_v1.types.ListSubscriptionsRequest(
    project=project_id,
    topic=topic_path,
    subscription=subscriptions,
    filter_='delivery_attempted = false'
)

发送请求并获取未送达消息的数量：

response = publisher.list_subscriptions(request=request)
num_unacked_messages = 0

for subscription in response:
    num_unacked_messages += subscription.num_unacked_messages

print("Number of undelivered messages:", num_unacked_messages)

这样就可以使用Python客户端库获取Pubsub中存在的未送达消息的数量了。

关于Pubsub的概念：Pubsub是一种消息传递服务，用于在分布式系统中传递和传播消息。它提供了可靠的、高吞吐量的消息传递，支持发布-订阅模式。

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