RabbitMQ and AMQP 0-9-1

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.

For around the last year we've maintained a 0-9-1-supporting branch of the broker and clients in Mercurial, and interested users have been running that version as it matures. Well, it's finally mature and we're now merging the 0-9-1 support into the default branch. This means it'll be in the next release.

At this point, you're probably wondering what the differences are between 0-8 and 0-9-1. Well, the good news is that the differences are not huge, and are entirely sensible. 0-9-1 mostly cleans up the 0-8 spec, explaining more clearly how the broker and clients are expected to behave in certain edge cases, and removing a whole load of ambiguity and half (or less) thought out features from 0-8.

In fact, if you're running 1.8.0 or later, you're already running a broker with most of the semantic changes from 0-9-1. But the wire protocol has changed a bit too, so it matters whether you're speaking 0-9-1 or 0-8.

For the Java and Erlang clients, we're intending to simply switch to supporting AMQP 0-9-1 exclusively in the next release. The .NET library already supports multiple protocols, so we're adding 0-9-1 as another option (and making it the default). For the broker we're going to support both AMQP 0-9-1 and AMQP 0-8. For any other client libraries we encourage you to speak to the library developer 😉

This means that this time it's safe to upgrade just your broker, or your broker and all your clients, but it's not safe to upgrade your clients without upgrading your broker!

Thank you for your attention.