RabbitMQ 4.2.2 is a maintenance release in the 4.2.x release series.

It is strongly recommended that you read 4.2.0 release notes in detail if upgrading from a version prior to 4.2.0.

Minimum Supported Erlang Version

RabbitMQ and Erlang/OTP Compatibility Matrix has more details on Erlang version requirements for RabbitMQ.

Nodes will fail to start on older Erlang releases.

Changes Worth Mentioning

Release notes can be found on GitHub at rabbitmq-server/release-notes.

Core Server

Bug Fixes

• Fixes a binding deletion-related memory leak in Khepri.

  This leak primarily affected systems with high binding churn.

  GitHub issue: #15024

• Corrected a performance regression around metric collection that could have a meaningful impact on quorum queues.

  GitHub issue: rabbitmq/seshat#16

• AMQP 1.0 link error frames did not have settlement set in certain failure scenarios, namely when attaching a link failed due to a missing source (queue or stream).

  GitHub issue: #15004

• AMQP 1.0 clients that publish messages without a body now get a clearer error message. Messages without a body explicitly violate the AMQP 1.0 specification.

  GitHub issue: #15048

• Default operator policy pre-configuration in rabbitmq.conf were unintentionally missing a key, default_policies.operator.$id.apply_to, for controlling what objects the policy applies to.

  GitHub issue: #14988

• Definition import is now more defensive when importing exchanges.

  GitHub issue: #15128

Enhancements

• More efficient Khepri (metadata store) querying.

  GitHub issue: rabbitmq/khepri#349

• Removed a cool down delay between stream chunk redelivery attempts.

  GitHub issue: #14766

• Stream data directory can now be configured via rabbitmq.conf.

  GitHub issue: #15014

• Stream replication: IP address family (IPv4 or IPv6) can now be configured via rabbitmq.conf.

  GitHub issue: #15012

OAuth 2 Plugin

Bug Fixes

• When multiple resource server IDs are configured, management UI login screen now provides a way to pre-select a specific resource ID before logging in.

  As part of this change, when multiple resource server IDs are configured, their order stored internally now reflects that in rabbitmq.conf.

  GitHub issue: #15044

Management Plugin

Bug Fixes

• GET /api/deprecated-features/used no longer returns an empty state field.

  GitHub issue: #14340

• Feature flag icons now contrast well when the dark mode is used in the UI.

  GitHub issue: #14620

• Corrected an invalid apply_to value (classic_queue instead of classic_queues) on the policy declaration form.

  Declaring a policy "directly" via the HTTP API was not affected.

  GitHub issue: #15054

Enhancements

• Queue declaration form fields were reordered so that the queue type dropdown comes before the virtual host.

  GitHub issue: #15017

• The order of configured OAuth 2 resource servers is now preserved in the management UI. Additionally, a resource server ID can now be pre-selected during service-provider-initiated logons.

  GitHub issue: #15044

Prometheus Plugin

Enhancements

• GET /metrics/per-object responses on systems with thousands of objections now takes 20-30% less time.

  GitHub issue: #15035

• Prometheus scraping endpoint responses are now streamed instead of being fully buffered before transmission. This reduces memory peak footprint and improves response times for nodes with a larger number of objects.

  GitHub issue: #15018

Bug Fixes

• Fixed a dependency loading issue with ddskerl (a Prometheus library dependency) that could cause stop_app to fail.

  GitHub issue: #15027

CLI Tools

Bug Fixes

• rabbitmq-queues quorum_status could run into an exception when a quorum queue member dies before recording any metrics.

  GitHub issue: #15003

Web MQTT Plugin

Bug Fixes

• The plugin now supports the mqttv3.1 WebSocket subprotocol in addition to mqtt, improving compatibility with older MQTT clients.

  GitHub issue: #15009

AWS Peer Discovery Plugin

Bug Fixes

• The plugin now uses IPv6 discovery endpoints in IPv6-only environments.

  GitHub issue: #14974

Tracing Plugin

Bug Fixes

• Trace files served via the management UI now include proper UTF-8 charset specification.

  GitHub issue: #14970

Trust Store Plugin

Bug Fixes

• The plugin now merges user-provided TLS options with the options it needs in a safer manner.

  GitHub issue: #15116

Dependency Changes

• khepri was upgraded to 0.17.3
• seshat was upgraded to 1.0.1