RabbitMQ 3.12.2 is a preview of a maintenance release in the 3.12.x release series.

Please refer to the upgrade section from the 3.12.0 release notes
if upgrading from a version prior to 3.12.0.

This release requires Erlang 25 and supports Erlang versions up to 26.0.x.
RabbitMQ and Erlang/OTP Compatibility Matrix has more details on
Erlang version requirements for RabbitMQ.

Minimum Supported Erlang Version

As of 3.12.0, RabbitMQ requires Erlang 25. Nodes will fail to start on older Erlang releases.

Users upgrading from 3.11.x (or older releases) on Erlang 25 to 3.12.x on Erlang 26
(both RabbitMQ and Erlang are upgraded at the same time) must consult
the v3.12.0 release notes first.

Changes Worth Mentioning

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

Core Server

Enhancements

• Free disk space monitor on Windows is now more selective in what errors are
  logged.

GitHub issue: #8837

Bug Fixes

• Queue recovery on node restart in certain conditions could run into an exception

GitHub issue: #8746

• file_handle_cache operations are now safer when handling non-existent keys.

GitHub issue: #8784

• Fixed a potential resource leak in at-least-once dead lettering from quorum queues.

GitHub issue: #8799

CLI Tools

Enhancements

• A new command, rabbitmqctl deactivate_free_disk_space_monitoring, can be used to (temporarily or permanently) disable
  free disk space monitoring on a node.

To re-activate it, use rabbitmqctl activate_free_disk_space_monitoring.

GitHub issue: #8801

AMQP 1.0 Plugin

Bug Fixes

• AMQP 1.0 clients that try to publish in a way that results in the message not being routed
  anywhere are now notified with a more sensible settlement status.

GitHub issue: #7823

Prometheus Plugin

Enhancements

• The plugin now filters out values that are undefined or NaN, simply excluding
  them from the API endpoint response.

Previously, if a metric was not computed for any reason (e.g. free disk space monitor
was disabled on the node), its value could end up being rendered as undefined or NaN,
two values that Prometheus scrapers cannot handle (for numerical types such as gauges).

GitHub issue: #8660

Management Plugin

Bug Fixes

• It was not possible to close a table column selection pane on
  screens that had little vertical space.

Contributed by @Antsthebul.

GitHub issue: #8701

STOMP Plugin

Bug Fixes

• This is a potentially breaking change.

  The plugin will now enforce maximum STOMP frame size. Frames larger than that
  size will be rejected. The default maximum size is 4 MiB. It can be increased or decreased:
  ``` ini

  increase maximum supported STOMP frame size to 10 MiB

  stomp.max_frame_size = 10485760
  To reduce it from the default 4 MiB to 2 MiB: ini

  2 MiB

  stomp.max_frame_size = 2097152
  ```

  GitHub issue: #8802

Shovel Plugin

Bug Fixes

• Shovel will gracefully stop when its destination (target) does not exist.
  Such shovels will then be periodically restarted to retry.

Contributed by @markus812498 (CloudAMQP).

GitHub issue: #8697

Web MQTT Plugin

Enhacements

• It is now possible to opt in to deactivate file handle cache use in the plugin:

ini web_mqtt.use_file_handle_cache = false

GitHub issue: #8790

Web STOMP Plugin

Enhacements

• It is now possible to opt in to deactivate file handle cache use in the plugin:

ini web_stomp.use_file_handle_cache = false

GitHub issue: #8790

Dependency Upgrades

• ra was upgraded to 2.6.3

Source Code Archives

To obtain source code of the entire distribution, please download the archive named rabbitmq-server-3.12.2.tar.xz
instead of the source tarball produced by GitHub.