英文:
Acknowledge messages in NSQ
问题
我是新手，对NSQ不太了解，想知道是否可以确认消息已被消费（就像Google PubSub一样）。我正在使用Golang，在阅读NSQ文档（https://github.com/nsqio/nsq/blob/v1.2.1/nsqd/channel.go#L350）时，我发现了FinishMessage方法，根据注释，它应该“成功丢弃正在处理的消息”。这是否可以视为确认？如果在NSQ中未确认消息，如何确保消息在被消费后不会再次被消费？
谢谢。
英文:
I'm new to NSQ and was wondering whether it is possible to acknowledge that a message was consumed (just like in Google PubSub). I'm using Golang, and while going through the NSQ documentation (https://github.com/nsqio/nsq/blob/v1.2.1/nsqd/channel.go#L350) I've found the method FinishMessage which according to its comment, it's supposed to successfully discards an in-flight message. Would that be considered the same as acknowledged? If a message is not acknowledged in NSQ, how is it ensured it's gone once consumed so it won't be consumed over again?
Thanks
答案1
得分: 1
NSQ在将消息发送给消费者后，会自动从队列中删除该消息。如果消费者在设定的超时时间内没有响应，NSQ会自动将消息重新放入队列中。
是的，根据你使用的编程语言客户端的不同，你需要发送'finish'指令。这里是Golang的文档链接：https://pkg.go.dev/github.com/nsqio/go-nsq#Finish
但是由于NSQ的设计方式，如果预期的操作不成功，你需要从你的应用程序中重新将消息放入队列中。
这是他们网站上的一段摘录：
NSQ保证消息至少会被传递一次，尽管重复的消息是可能的。消费者应该预期到这一点，并进行去重或执行幂等操作。
这个保证是作为协议的一部分来执行的，工作原理如下（假设客户端已成功连接并订阅了一个主题）：
- 客户端表示准备好接收消息
- NSQ发送一条消息并在本地临时存储数据（以防重新放入队列或超时）
- 客户端回复FIN（完成）或REQ（重新放入队列），表示成功或失败。如果客户端没有回复，NSQ将在可配置的持续时间后超时并自动重新放入消息。
你可以在这里阅读更多信息：https://nsq.io/overview/design.html
希望我的回答对你有帮助。
英文:
NSQ automatically removes a message from the queue after sending it to a consumer. And automatically re-queues the message if there is no response from the consumer after a set timeout.
And yes, depending on which programming language client you are using you have to send 'finish'.
Here are the docs for Golang
https://pkg.go.dev/github.com/nsqio/go-nsq#Finish
But because of the way NSQ is designed you have to re-queue a message from your app if the intended action was not successful.
Here is an excerpt from their website
>NSQ guarantees that a message will be delivered at least once, though duplicate messages are possible. Consumers should expect this and de-dupe or perform idempotent operations.
>This guarantee is enforced as part of the protocol and works as follows (assume the client has successfully connected and subscribed to a topic):
>1. client indicates they are ready to receive messages
> 2. NSQ sends a message and temporarily stores the data locally (in the event of re-queue or timeout)
> 3. client replies FIN (finish) or REQ (re-queue) indicating success or failure respectively. If client does not reply NSQ will timeout after
> a configurable duration and automatically re-queue the message)
You can read more here: https://nsq.io/overview/design.html
Hope my answer helps you.
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