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RabbitMQ 4.2.0
RabbitMQ 4.2.0 is a new feature release.
Breaking Changes and Compatibility Notes
Default value for AMQP 1.0 durable field.
Starting with RabbitMQ 4.2, if a sending client omits the header section, RabbitMQ assumes the durable field to be false complying with the AMQP 1.0 spec:
<field name="durable" type="boolean" default="false"/>
AMQP 1.0 apps or client libraries must set the durable field of the header section to true to mark the message as durable.
Team RabbitMQ recommends client libraries to send messages as durable by default. All AMQP 1.0 client libraries maintained by Team RabbitMQ send messages as durable by default.
Features
Incoming and Outgoing Message Interceptors for native protocols
Incoming and outgoing messages can now be intercepted on the broker. This works for AMQP 1.0, AMQP 0.9.1, and MQTT.
What the interceptor does is entirely up to its implementation, for example it can validate message metadata, add annotations, or perform arbitrary side effects. Custom interceptors can be developed and integrated via plugins.
Two new optional built-in interceptors were added to RabbitMQ:
- Timestamps for outgoing messages
- Setting client ID of publishing MQTT client
Detailed information can be found in the Message Interceptor documentation.
Khepri enabled by default
RabbitMQ supports two databases to store metadata such as virtual hosts, topology, runtime parameters, policies, internal users and so on: Mnesia and Khepri. That metadata store is also at the heart of clustering in RabbitMQ. As of RabbitMQ 4.2.0, Khepri is the default metadata store for new deployments.
Khepri is based on the same Raft consensus algorithm used by quorum queues and streams. The goal is to have a consistent well defined behaviour around all queries and updates of metadata across an entire cluster, especially when the cluster suffers increased latency or network issues for instance. It also comes with increased performance in several use cases, even though this was not a goal.
A new RabbitMQ 4.2.0+ node will use Khepri by default. If you upgrade an existing node or cluster, it will continue to use whatever metadata store it was using so far.
If you did not enable Khepri yet, it is recommended you enable it:
rabbitmqctl enable_feature_flag khepri_db
Khepri will become mandatory in a future minor version. Mnesia support will be dropped in a future major version. These exact versions are to be decided.