Merge pull request #9136 from rabbitmq/mergify/bp/v3.12.x/pr-9135

3.12.3 release notes (backport #9135)

Author: michaelklishin

release-notes/3.12.3.md

@@ -0,0 +1,106 @@
+RabbitMQ `3.12.3` is 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
+
+ * Certain diagnostics operations during rolling upgrades from 3.10 to 3.11 could fail
+   if the `listener_records_in_ets` feature flag was enabled in the middle of the upgrade.
+
+   Contributed by @gomoripeti (CloudAMQP).
+
+   GitHub issue: [#8984](https://github.com/rabbitmq/rabbitmq-server/pull/8984)
+
+ * On Windows, PowerShell will no longer be used as a fallback for `handle.exe`
+   for computing how many file and socket handles a node uses.
+
+   If a user does not have `handle.exe`` installed in the `PATH`` of their Windows system,
+   a message will be logged once, and then the total handles being used will be set to 0.
+
+   PowerShell ended up being a CPU-intensive alternative that's not worth the gains
+   for many installations.
+
+   GitHub issue: [#8700](https://github.com/rabbitmq/rabbitmq-server/issues/8700)
+
+ * Node maintenance state was not replicated to all nodes, even though it was accessible
+   from any node (and for any node).
+
+   GitHub issue: [#9005](https://github.com/rabbitmq/rabbitmq-server/pull/9005)
+
+
+### CLI Tools
+
+#### Enhacements
+
+ * Some warnings were emitted even when `--formatter` was set to `json`.
+
+   GitHub issue: [#8912](https://github.com/rabbitmq/rabbitmq-server/issues/8912)
+
+
+### MQTT Plugin
+
+#### Bug Fixes
+
+ * MQTT connections could run into an exception when a queue it consumed from was temporarily
+   unavailable (e.g. was undergoing a leader election).
+
+   GitHub issue: [#9040](https://github.com/rabbitmq/rabbitmq-server/pull/9040)
+
+#### Enhancements
+
+ * When QoS 0 consumers consistently do not keep up with publishers, some messages will be dropped
+   to avoid runaway resource usage.
+
+   Now the number of dropped messages will be reflected in the dropped message metric,
+   [together with unroutable messages](https://www.rabbitmq.com/reliability.html#routing).
+
+   GitHub issue: [#9080](https://github.com/rabbitmq/rabbitmq-server/pull/9080)
+
+
+### HTTP AuthN/AuthZ Backend Plugin
+
+#### Bug Fixes
+
+ * AMQP 1.0 client connections were refused with this plugin.
+
+   GitHub issue: [#9043](https://github.com/rabbitmq/rabbitmq-server/issues/9043)
+
+
+### LDAP AuthN/AuthZ Backend Plugin
+
+#### Bug Fixes
+
+ * AMQP 1.0 client connections were refused with this plugin.
+
+   GitHub issue: [#9043](https://github.com/rabbitmq/rabbitmq-server/issues/9043)
+
+
+## Dependency Upgrades
+
+ * `osiris` was upgraded to [`1.6.3`](https://github.com/rabbitmq/osiris/tags)
+
+## Source Code Archives
+
+To obtain source code of the entire distribution, please download the archive named `rabbitmq-server-3.12.3.tar.xz`
+instead of the source tarball produced by GitHub.