How does RabbitMQ ensure that messages are not duplicated?

RabbitMQ itself does not provide a mechanism for message deduplication, but there are ways to ensure that messages are not duplicated.

1. Use a unique message identifier: Generate a unique identifier for each message when it is published, and store it in a database or cache. When a consumer receives a message, check if the identifier already exists in the database or cache. If it does, it means the message has already been processed and can be ignored.
2. Idempotent processing: Implementing idempotent logic on the consumer side means that the same message can be processed repeatedly, but only one result will be produced. This is achieved by using a unique identifier or business logic check in the consumer-side processing to ensure that duplicates are avoided.
3. There are third-party message deduplication plugins in the RabbitMQ community, such as rabbitmq-message-deduplication and rabbitmq-deduplication, that can be used to achieve message deduplication.

It is necessary to choose the appropriate method based on specific business needs and scenarios to ensure that messages are not duplicated.