How to implement delayed queues in RabbitMQ?

RabbitMQ itself does not directly support delayed queues, but delayed queues functionality can be achieved through some techniques. One common implementation method is as follows:

1. Create two queues: original queue and delayed queue.
2. Send the message to a delayed queue and set the message’s expiration time to match the delay time.
3. Create a consumer that receives messages from a delayed queue.
4. In the consumer, determine if the message is expired. If the message is expired, resend it to the original queue; if the message is not expired, resend it to the delayed queue.
5. Create another consumer to receive and process messages from the original queue.

By using this method, the functionality of a delayed queue can be achieved where messages can only be consumed after a certain period of time.