4.0.4 release notes

Author: michaelklishin

release-notes/4.0.4.md

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+## RabbitMQ 4.0.4
+
+RabbitMQ `4.0.4` is a maintenance release in the `4.0.x` [release series](https://www.rabbitmq.com/release-information).
+
+Starting June 1st, 2024, community support for this series will only be provided to [regularly contributing users](https://github.com/rabbitmq/rabbitmq-server/blob/main/COMMUNITY_SUPPORT.md) and those
+who hold a valid [commercial support license](https://tanzu.vmware.com/rabbitmq/oss).
+
+It is **strongly recommended** that you read [4.0 release notes](https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.0.1)
+in detail if upgrading from a version prior to `4.0.0`.
+
+
+### Minimum Supported Erlang Version
+
+This release requires Erlang 26 and supports Erlang versions up to `27.1.x`.
+[RabbitMQ and Erlang/OTP Compatibility Matrix](https://www.rabbitmq.com/docs/which-erlang) 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](https://github.com/rabbitmq/rabbitmq-server/tree/v4.0.x/release-notes).
+
+### Core Broker
+
+#### Bug Fixes
+
+ * In rare cases quorum queue could end up without an elected leader because
+   chosen candidate replica was not verified for aliveness.
+
+   Contributed by @Ayanda-D.
+
+   GitHub issues: [#12727](https://github.com/rabbitmq/rabbitmq-server/pull/12727), [#10423](https://github.com/rabbitmq/rabbitmq-server/discussions/10423), [#12701](https://github.com/rabbitmq/rabbitmq-server/discussions/12701)
+
+ * Quorum queue follower replicas that have falled behind the leader could
+   run into an exception after installing a snapshot.
+
+   GitHub issue: [#12635](https://github.com/rabbitmq/rabbitmq-server/issues/12635)
+
+ * Clusters with a large number of streams could run into confusing timeout
+   exceptions.
+
+   GitHub issue: [#12693](https://github.com/rabbitmq/rabbitmq-server/pull/12693)
+
+ * Stream members could fail to start when their data directories had externally added files,
+   for example, metadata of certain file systems.
+
+   GitHub issue: [#12688](https://github.com/rabbitmq/rabbitmq-server/issues/12688)
+
+ * Fetching metrics of AMQP 1.0 connections could fail with an exception.
+
+   GitHub issue: [#12700](https://github.com/rabbitmq/rabbitmq-server/pull/12700)
+
+#### Enhancements
+
+ * Policy changes are now periodicaly re-applied (only if necessary) to quorum queues.
+   Quorum queues that did not have an online elected leader at the time
+   of policy change would now eventually "pick up" the settings from that policy.
+
+   Contributed by @LoisSotoLopez.
+
+   GitHub issue: [#12667](https://github.com/rabbitmq/rabbitmq-server/pull/12667)
+
+ * Clusters with many streams and stream consumers will see a reduced per-stream CPU and network I/O
+   footprint.
+
+   GitHub issue: [#12685](https://github.com/rabbitmq/rabbitmq-server/pull/12685)
+
+ * Clusters now can optionally be tagged with key-value pairs (cluster tags). The tags will
+   be reported by `rabbitmq-diagnostics cluster_status` and the `GET /api/overview` HTTP API endpoint.
+
+   Note that the Prometheus scraper API endpoint intentionally omits them because this kind of
+   metadata in Prometheus is considered to be [deployment and not application metadata](https://github.com/rabbitmq/rabbitmq-server/issues/12552#issuecomment-2424985095).
+
+   The tags are configured using `rabbitmq.conf`:
+
+   ```ini
+   cluster_tags.environment = production
+
+   cluster_tags.region = us-east
+   cluster_tags.az = us-east-3
+   ```
+
+   Contributed by @SimonUnge.
+
+   GitHub issue: [#12552](https://github.com/rabbitmq/rabbitmq-server/issues/12552)
+
+ * Nodes now can optionally be tagged with key-value pairs (node tags). The tags will
+   be reported by `rabbitmq-diagnostics status` and the `GET /api/overview` HTTP API endpoint.
+
+   Note that the Prometheus scraper API endpoint intentionally omits them because this kind of
+   metadata in Prometheus is considered to be [deployment and not application metadata](https://github.com/rabbitmq/rabbitmq-server/issues/12552#issuecomment-2424985095).
+
+   The tags are configured using `rabbitmq.conf`:
+
+   ```ini
+   cluster_tags.environment = production
+
+   cluster_tags.region = us-east
+   cluster_tags.az = us-east-3
+   ```
+
+   Contributed by @SimonUnge.
+
+   GitHub issue: [#12703](https://github.com/rabbitmq/rabbitmq-server/pull/12703)
+
+ * When a [max length](https://www.rabbitmq.com/docs/maxlength) limit is applied to a quorum queue with a larger backlog (e.g. millions of messages),
+   the deletion of excess messages now carries a significantly more moderate spike in memory footprint
+   of the queue.
+
+   GitHub issue: [#12608](https://github.com/rabbitmq/rabbitmq-server/issues/12608)
+
+
+### CLI Tools
+
+#### Bug Fixes
+
+ * `rabbitmq-diagnostics check_if_any_deprecated_features_are_used` now takes more deprecated features
+   into account.
+
+   GitHub issue: [#12734](https://github.com/rabbitmq/rabbitmq-server/pull/12734), [#12738](https://github.com/rabbitmq/rabbitmq-server/pull/12738)
+
+
+### MQTT Plugin
+
+#### Bug Fixes
+
+ * A message with expiration (TTL) set, that was published by an AMQP 0-9-1 publusher,
+   could not be converted for an MQTT consumer.
+
+   GitHub issue: [#12711](https://github.com/rabbitmq/rabbitmq-server/pull/12711)
+
+ * When x.509 (TLS) certificate-based authentication was used, two keys that controlled
+   what SAN (Subject Alternative Name) fields were used to fetch client identity did not
+   have any effect when used in `rabbitmq.conf`.
+
+   Partially contributed by @janezturk.
+
+   GitHub issue: [#12618](https://github.com/rabbitmq/rabbitmq-server/pull/12618)
+
+
+### Prometheus Plugin and Grafana Dashboards
+
+#### Bug Fixes
+
+ * Tweaks for Grafana 11.3 compatibility.
+
+   Contributed by @anhanhnguyen.
+
+   GitHub issue: [#12720](https://github.com/rabbitmq/rabbitmq-server/pull/12720)
+
+
+### Management Plugin
+
+#### Enhancements
+
+ * The endpoint that creates bindings now uses a much smaller HTTP request body
+   size limit by default. Unlike the definition upload endpoint that accepts
+   large definition documents, bindings do not need the generous multi-MiB limit.
+
+   Note that the default HTTP request body size limit [can be configured](https://www.rabbitmq.com/docs/management#http-body-size-limit),
+   for example, to reduce it across the board.
+
+   GitHub issue: [#12697](https://github.com/rabbitmq/rabbitmq-server/pull/12697)
+
+ * Improved alignment of optional queue arguments on the queue declaration page.
+
+   Contributed by @markus812498.
+
+   GitHub issue: [#12678](https://github.com/rabbitmq/rabbitmq-server/pull/12678)
+
+
+### OAuth 2 Plugin
+
+#### Bug Fixes
+
+ * When configuring [multiple resource servers](https://www.rabbitmq.com/docs/oauth2#multiple-resource-servers-configuration),
+  `additional_scopes_key` was not taken into account, which means some scopes were not considered
+  when making an authorization decision.
+
+  Contributed by @Hathoute.
+
+   GitHub issue: [#12750](https://github.com/rabbitmq/rabbitmq-server/issues/12750)
+
+
+### Debian Package
+
+#### Enhancements
+
+ * The package now list Erlang 27.x as supported versions.
+
+   GitHub issue: [#12603](https://github.com/rabbitmq/rabbitmq-server/issues/12603)
+
+### RPM Package
+
+#### Enhancements
+
+ * The package now list Erlang 27.x as supported versions.
+
+   GitHub issue: [#12603](https://github.com/rabbitmq/rabbitmq-server/issues/12603)
+
+
+### Dependency Changes
+
+  * `osiris` was upgraded to [`1.8.4`](https://github.com/rabbitmq/osiris)
+
+
+## Source Code Archives
+
+To obtain source code of the entire distribution, please download the archive named `rabbitmq-server-4.0.4.tar.xz`
+instead of the source tarball produced by GitHub.