Merge pull request #8816 from rabbitmq/mk-3.12.2-release-notes

3.12.2 release notes

Author: michaelklishin

release-notes/3.12.2.md

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+RabbitMQ `3.12.2-beta.1` is a preview of a maintenance release in the `3.12.x` [release series](https://www.rabbitmq.com/versions.html).
+
+Please refer to the upgrade section from the [3.12.0 release notes](https://github.com/rabbitmq/rabbitmq-server/releases/tag/v3.12.0)
+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](https://www.rabbitmq.com/which-erlang.html) 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](https://github.com/rabbitmq/rabbitmq-server/releases/tag/v3.12.0) first.
+
+
+## Changes Worth Mentioning
+
+Release notes can be found on GitHub at [rabbitmq-server/release-notes](https://github.com/rabbitmq/rabbitmq-server/tree/v3.12.x/release-notes).
+
+### Core Server
+
+#### Bug Fixes
+
+ * Queue recovery on node restart in certain conditions could run into an exception
+
+   GitHub issue: [#8746](https://github.com/rabbitmq/rabbitmq-server/issues/8746)
+
+ * `file_handle_cache` operations are now safer when handling non-existent keys.
+
+   GitHub issue: [#8784](https://github.com/rabbitmq/rabbitmq-server/issues/8784)
+
+
+### 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](https://github.com/rabbitmq/rabbitmq-server/pull/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](https://github.com/rabbitmq/rabbitmq-server/issues/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](https://github.com/rabbitmq/rabbitmq-server/issues/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](https://github.com/rabbitmq/rabbitmq-server/pull/8701)
+
+
+### STOMP Plugin
+
+#### Bug Fixes
+
+ * 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:
+
+   ``` ini
+   # increase maximum supported STOMP frame size to 10 MiB
+   stomp.max_frame_size = 10485760
+   ```
+
+   GitHub issue: [#8802](https://github.com/rabbitmq/rabbitmq-server/pull/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](https://github.com/rabbitmq/rabbitmq-server/pull/8697)
+
+
+### Web MQTT Plugin
+
+#### Enhacements
+
+ * It is now possible to opt in to deactivate file handle cache use in the plugin.
+
+   GitHub issue: [#8790](https://github.com/rabbitmq/rabbitmq-server/pull/8790)
+
+
+### Web STOMP Plugin
+
+#### Enhacements
+
+ * It is now possible to opt in to deactivate file handle cache use in the plugin.
+
+   GitHub issue: [#8790](https://github.com/rabbitmq/rabbitmq-server/pull/8790)
+
+
+## Dependency Upgrades
+
+None in this release.
+
+## 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.