问题
I have exchange and queue. Producer doesn't need consumption confirmation, but messages in some cases can be un-processable by consumer in current moment, because of lack of other data. Because of this, I want to return those messages to the end of queue. How to do this? Or is it done automatically when I reject message?
Flow:
- Message1 gets consumed and creates some record in database.
- Message2 gets consumed and checks if there is record in database, and if yes, then it updates the record. If there is no record in database, message should be returned to the end of queue.
So there is message ordering problem and in general situation I get messages in order, because most of components deliver their messages correctly. I want to solve potential situation, when Producer of Message1 wasn't able to put message to exchange immediately because of heavy load or other reason. In this situation, Message2 will be consumed first but there will be no sufficient informations in database to process it. I want this message to be returned back to queue, but be sure that this Message2 will go to the tail of queue. If it will go to head, I will get infinite loop if I use only one queue.
Side question is, if it's possible to track how many times consumers tried to process message but returned it. If there is possibility to put message to the tail of queue like I described before, but for some reason Producer of Message1 died, and there will be no Message1, I want to make Message2 dead after some number of retries or some time.
回答1:
RabbitMQ always puts rejected messages at the head of the queue. To put them at the tail, you will have to publish them yourself (e.g. using RabbitTemplate). You can add a header with a count of retries.
来源：https://stackoverflow.com/questions/44704950/return-message-to-the-end-of-queue-in-rabbitmq