Since the beginning, RabbitMQ has implemented the 0-8 version of the AMQP specification. This was the first publicly-available version, but there’s been plenty of development since then. In particular, we’ve wanted to support the 0-9-1 version of AMQP for a while now.
Support for AMQP’s
basic.reject just landed on default. It’s taken this long because we couldn’t agree on a single set of semantics that followed the specification, was actually useful, and wasn’t too complicated to implement.