4.2.0 release notes updates for beta.2

Author: michaelklishin

release-notes/4.2.0.md

@@ -103,3 +103,129 @@ rabbitmqctl enable_feature_flag khepri_db
 
 Khepri will become mandatory in a future minor version. Mnesia support will be
 dropped in a future major version. These exact versions are to be decided.
+
+### Local Shovels
+
+In addition to AMQP 0-9-1 and AMQP 1.0, Shovels
+now support a new "protocol" option called `local`.
+
+These specialized shovels are internally based on AMQP 1.0 but instead of
+separate TCP connections, use the intra-cluster connections
+between cluster nodes and the internal API for consumption, publishing
+and AMQP 1.0 credit flow.
+
+Such shovels can only be used for consuming and publishing
+within the same cluster, not across clusters, but can offer
+higher throughput and use fewer resources per connections
+than their AMQP 0-9-1 and AMQP 1.0 counterparts.
+
+
+
+## Upgrading to 4.2.0
+
+### Documentation guides on upgrades
+
+See the [Upgrading guide](https://www.rabbitmq.com/docs/upgrade) for documentation on upgrades and [GitHub releases](https://github.com/rabbitmq/rabbitmq-server/releases)
+for release notes of individual releases.
+
+This release series supports upgrades from `4.1.x`, 4.0.x` and `3.13.x`.
+
+[Blue/Green Deployment](https://www.rabbitmq.com/docs/blue-green-upgrade)-style upgrades are avaialble for migrations
+from RabbitMQ `3.12.x` series.
+
+### New Required Feature Flags
+
+None. The required feature flag set is the same as in `4.1.x` and `4.0.x`.
+
+### Mixed version cluster compatibility
+
+RabbitMQ 4.2.0 nodes can run alongside `4.1.x` and `4.0.x` nodes. `4.2.x`-specific features can only be made available when all nodes in the cluster upgrade to 4.2.0 or a later patch release in the new series.
+
+While operating in mixed version mode, some aspects of the system may not behave as expected.
+Once all nodes are upgraded to 4.1.0, these irregularities will go away.
+
+Mixed version clusters are a mechanism that allows rolling upgrade and are not meant to be run for extended
+periods of time (no more than a few hours).
+
+### Recommended Post-upgrade Procedures
+
+This version does not require any additional post-upgrade procedures
+compared to other versions.
+
+
+
+## Changes Worth Mentioning
+
+This section is **incomplete** and will be expanded as 4.2 approaches its release candidate stage.
+
+### Core Server
+
+#### Enhancements
+
+ * In clusters with a larger number of quorum queues (say, tens of thousands),
+   quorum queue leadership transfer is now performed gradually and not all at once.
+
+   Previously tens of thousands of concurrent leader elections
+   could result in timeouts and some quorum queues ending up
+   without an elected leader.
+
+   GitHub issue: [#14401](https://github.com/rabbitmq/rabbitmq-server/pull/14401)
+
+ * When a configured [authentication or authorization backend](https://www.rabbitmq.com/docs/access-control#backends) comes from a known
+   plugin but the plugin is not enabled, the node will now refuse to start.
+
+   Previously the node would boot but client connections would fail because
+   of the missing backend modules.
+
+   GitHub issues: [#13783](https://github.com/rabbitmq/rabbitmq-server/discussions/13783), [#14408](https://github.com/rabbitmq/rabbitmq-server/pull/14408)
+
+ * Similarly to the number of [queues](https://github.com/rabbitmq/rabbitmq-server/pull/11196) and [virtual hosts](https://github.com/rabbitmq/rabbitmq-server/pull/7798), it is now possible
+   to configure a limit on the cluster-wide number of exchanges that applications
+   can create:
+
+   ```ini
+   # Applications won't be able to decalre more than 200 exchanges
+   # (including the protocol-standard pre-declared ones) in the cluster
+   cluster_exchange_limit = 200
+   ```
+
+#### Bug Fixes
+
+ * `default_password`, `ssl_options.password` now can tell between a generated random password
+   value and an [encrypted value](https://www.rabbitmq.com/docs/configure#configuration-encryption) better.
+
+   Encrypted values must be prefixed with `encrypted:`. All other values, including
+   generated passwords that contain a colon (`:`), will be considered non-encrypted ones.
+
+   GitHub issue: [#14365](https://github.com/rabbitmq/rabbitmq-server/pull/14365)
+
+ * Import of definition files that contained topic exchange permissions failed.
+
+   GitHub issue: [#14409](https://github.com/rabbitmq/rabbitmq-server/pull/14409)
+
+
+### Stream Plugin
+
+#### Bug Fixes
+
+ * Stream client connections that authenticate using a JWT token (OAuth 2) have
+   to periodically renew their JWT tokens. Should such an update fail,
+   the RabbitMQ Stream Protocol connection will be immediately closed.
+
+   In addition, stream connections now verify that the newly obtained JWT
+   token still grants access to the virtual host the client is connected to.
+
+   GitHub issues: [#14403](https://github.com/rabbitmq/rabbitmq-server/pull/14403), [#14406](https://github.com/rabbitmq/rabbitmq-server/pull/14406)
+
+
+
+### Dependency Changes
+
+ * `ra` was upgraded to [`2.17.1`](https://github.com/rabbitmq/ra/releases)
+ * `cuttlefish` was upgraded to [`3.5.0`](https://github.com/kyorai/cuttlefish/releases)
+
+
+## Source Code Archives
+
+To obtain source code of the entire distribution, please download the archive named `rabbitmq-server-4.2.0.tar.xz`
+instead of the source tarball produced by GitHub.