Chapter 4. Queues

Message Queues are the mechanism for consuming applications to subscribe to messages that are of interest.

Queues receive messages from exchanges, and buffer those messages until they are consumed by message consumers. Those message consumers can browse the queue, or can acquire messages from the queue. Messages can be returned to the queue for redelivery, or they can be rejected by a consumer.

Multiple consumers can share a queue, or a queue may be exclusive to a single consumer.

Message producers can create and bind a queue to an exchange and make it available for consumers, or they can send to an exchange and leave it up to consumers to create queues and bind them to the exchange to receive messages of interest.

Temporary private message queues can be created and used as a response channel. Message queues can be set to be deleted by the broker when the application using them disconnects. They can be configured to group messages, to update messages in the queue with newly-arriving copies of messages, and to prioritize certain messages.

Another way of managing message queues, specifically in the area of message Time To Live (TTL), is to use the --queue-purge-interval. While this is not a qpid-config option, it is worth understanding that message TTL can be configured, and when the purge attempt is successful the messages are subsequently removed.

Refer to Section 3.3.7, “Queue Options” for details about this broker option.