英文:
AWS SQS polling
问题
I don't understand the need to configure short and long polling directly on the queue. Say I create an sqs queue and I want to check the queue for messages once every hour with java. Then I just need to create a method annotated with @Scheduled(fixedRate = 3600000) and in the method I call sqsClient.receiveMessage and that's it. If I want short polling then I can just reduce the fixedRate to call my method every 5 seconds for example.
我不理解为什么需要直接在队列上配置短轮询和长轮询。比如，我创建了一个 SQS 队列，我想每小时用 Java 检查队列中的消息。然后，我只需要创建一个带有 @Scheduled(fixedRate = 3600000) 注解的方法，在该方法中调用 sqsClient.receiveMessage 就可以了。如果我想要短轮询，我可以将 fixedRate 缩短，例如每 5 秒调用一次我的方法。
I already read:
> waitTimeSeconds(): The duration (in seconds) for which the call waits
> for a message to arrive in the queue before returning.
>
> When passing a value for waitTimeSeconds (maximum of 20 seconds), the
> call will block while there are no messages available in the queue.
> However, if there is a message (or a message comes during that time
> period), it will immediately return with messages.
我已经阅读过：
> waitTimeSeconds()：调用在返回之前等待消息到达队列的持续时间（以秒为单位）。
>
> 当传递 waitTimeSeconds 的值（最长为 20 秒）时，如果队列中没有可用的消息，调用将会阻塞。然而，如果在这段时间内有消息到达（或者在此期间有消息到达），它将立即返回带有消息。
What is it, another polling configuration within my polling configuration with @Scheduled? I don't get it. Also the max value is 20 seconds and I really don't need to check my queue that frequently. So do I just set Receive message wait time to 1 so I get the specificities of long polling (check all servers for messages) and ignore its existence because I don't need it? What is the usecase of it?
这是什么意思，是我的 @Scheduled 轮询配置中的另一种轮询配置吗？我不明白。而且最大值是 20 秒，我确实不需要那么频繁地检查我的队列。所以我只需将接收消息等待时间设置为 1，以获得长轮询的特性（检查所有服务器的消息），并忽略它的存在，因为我不需要它吗？它的用例是什么？
英文:
I don't understand the need to configure short and long polling directly on the queue.
Say I create an sqs queue and I want to check the queue for messages once every hour with java.
Then I just need to create a method annotated with @Scheduled(fixedRate = 3600000) and in the method I call sqsClient.receiveMessage and that's it.
If I want short polling then I can just reduce the fixedRate to call my method every 5 seconds for example.
I already read:
> waitTimeSeconds(): The duration (in seconds) for which the call waits
> for a message to arrive in the queue before returning.
>
> When passing a value for waitTimeSeconds (maximum of 20 seconds), the
> call will block while there are no messages available in the queue.
> However, if there is a message (or a message comes during that time
> period), it will immediately return with messages.
What is it, another polling configuration within my polling configuration with @Scheduled ? I don't get it. Also the max value is 20 seconds and I really don't need to check my queue that frequently.
So do I just set Receive message wait time to 1 so I get the specificities of long polling (check all servers for messages) and ignore its existence because I don't need it ?
What is the usecase of it ?
答案1
得分: 3
如果您的需求是每小时检查消息，则 waitTimeSeconds() 对您来说不相关。
通常在高流量情况下使用，其中需要连续获取消息。为此，编写一个'消费者'来持续轮询队列。为了减少调用次数，可以指定最多等待 20 秒。
通过指定等待时间，它表示：“如果队列中没有消息，请等待 20 秒然后再对此 API 调用提供响应。但是，如果有消息可用，请立即返回。”
用例是一个希望在消息进入队列时能够快速响应的系统。
英文:
If your requirement is to check for messages every hour, then waitTimeSeconds() is not relevant for you.
It is normally used in high-volume situations where messages are continuously wanted. For this, a 'consumer' is written that keeps polling the queue. To minimise the number of calls, a Wait Time of up to 20 seconds can be specified.
By specifying a Wait Time it is saying: "If there are no messages in the queue, wait 20 seconds before providing a response to this API call. However, please return immediately if a message becomes available."
The use-case would be for a system that wants to respond very quickly when a message enters the queue.
答案2
得分: 0
短轮询是在客户端希望尽快获取/处理每条消息（低延迟）时使用的。长轮询是当AWS等待X秒，然后轮询请求返回数据时使用的。这种方法很少使用，因为需要等待超时才能处理消息。理论上，这可能会在队列完全加载的情况下产生更高的吞吐量，但这种情况相当罕见。
英文:
Short polling, is used when 'the client' wants to get/process every message as fast as possible (low latency).
Long polling is used when AWS wait for X seconds, before the poll request returns data. This is rarely used, as it required a timeout to occur before the messages are processed. Theoretically, this may yield higher throughput, but only in scenarios where the queue is fully loaded, which is quite rare.
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