RabbitMQ `4.3.0-rc.0` is a preview of a new feature release. ## Breaking Changes and Compatibility Notes ### Mnesia and Parition Handling Strategies are Removed Since only `4.2.x` clusters can upgrade to `4.3.0` [in place](https://www.rabbitmq.com/docs/upgrade), this won't be a breaking change for nearly all instalations but All partition handling-related keys in `rabbitmq.conf` will be accepted by `4.3.0` nodes but won't have any effect: * `cluster_partition_handling` * `cluster_partition_handling.pause_if_all_down.recover` * `cluster_partition_handling.pause_if_all_down.nodes.$name` Still, Team RabbitMQ recommends removing the above keys from `rabbitmq.conf` before or shortly after upgrading. ### Classic Queues v1 Storage (CQv1) is Removed This release removes the original classic queue storage implementation these days known as CQv1. A 2nd generation implementation called CQv2 has been adopted as the default starting with `4.2.0`. This means that attempts to declare a queue using the following [optional queue arguments](https://www.rabbitmq.com/docs/queues#optional-arguments) will fail: * `x-queue-mode` set to any value * `x-queue-version` set to `1` Existing classic queues upgraded to CQv2 during an earlier upgrade to `4.2.x` will continue operating as usual. ### Consumer Timeouts are No Longer Evaluated for Classic Queues and Streams This release moves consumer timeout handling responsibility into the queues themselves. Also, all protocols (except the stream protocol) now evaluate consumer timeout for queue types that support them. Classic queues and streams never evaluate consumer timeouts as their use cases cause less demand for it. ## Release Highlights ### Khepri is Now The Only Metadata Store As of this release, Khepri is the only [metadata store](https://www.rabbitmq.com/docs/metadata-store) supported by RabbitMQ: Mnesia was removed completely. In practical operational terms, this means that 1. For a cluster to be available, a majority of nodes must be online at all times 2. Failure and partition recovery in a RabbitMQ cluster is now significantly simpler and uniform: all components that have replicated state (Khepri, quorum queues, streams) recover per Raft recovery semantics ### Quorum Queues Enhancements This release upgrades the [Ra](https://github.com/rabbitmq/ra) dependency to `3.x` and introduces a new (8th) version of the quorum queue state machine with several new features and optimisations: * **Strict priority queues** with per-priority message counts, correct redelivery ordering, and priority-aware message expiration * **Delayed retry** for quorum queues: configurable increasing backoff when messages are returned * **Consumer timeout** for quorum queues: configurable timeout for unacknowledged messages, with protocol-specific handling for AMQP 1.0 and MQTT * **Recovery snapshots** and **snapshot throttling** to reduce recovery time and improve snapshotting decisions * **Memory optimisations** including compact message references, optimised tuple storage for delayed keys, and removal of `rabbit_fifo_index` usage ## Upgrading to 4.3.0 ### 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 `4.2.x`. Upgrades from earlier series are **not** supported: users must upgrade to the latest available `4.2.x` patch release before upgrading to `4.3.0`. ### New Required Feature Flags All feature flags introduced in `4.2.0` and earlier are required, including the following: * `rabbitmq_4.2.0` * `rabbitmq_4.1.0` * `rabbitmq_4.0.0` * `khepri_db` * `quorum_queue_non_voters` * `message_containers_deaths_v2` Enable all required feature flags before upgrading to `4.3.0`. If your RabbitMQ cluster had plugin `rabbitmq_amqp1_0` enabled in RabbitMQ `3.13.x` (and your cluster still serves AMQP 1.0 client connections in `4.x`), your cluster should do at least one rolling update **after** enabling feature flag `rabbitmq_4.0.0` but **before** upgrading to `4.3.0`. ### Deprecated Features In `4.3.0` the [deprecation phase](https://www.rabbitmq.com/docs/deprecated-features) of the following features advanced from `permitted_by_default` to `denied_by_default`: * `amqp_address_v1` * `amqp_filter_set_bug` * `global_qos` * `queue_master_locator` * `transient_nonexcl_queues` And the deprecated feature `ram_node_type` has been removed. ### Mixed version cluster compatibility RabbitMQ 4.3.0 nodes can run alongside `4.2.x` in the same cluster. Mixed version clusters are a mechanism that allows rolling upgrades 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 ### Core Server #### Enhancements * When a message is rejected by a queue, RabbitMQ now provides the queue name and rejection reason to AMQP 1.0 publishers in the `Rejected` outcome. This is particularly useful when multiple queues are bound to an exchange, as it allows publishers to identify which specific queue out of several target queues rejected the message and why (e.g., maximum queue length reached or queue unavailable). Previously, publishers had no way to determine which queue rejected their message or the reason for rejection. The queue name and reason are included in the `info` field of the `Rejected` outcome's `error` field: * `queue: <queue name>` * `reason: maxlen | unavailable` GitHub issue: [#15075](https://github.com/rabbitmq/rabbitmq-server/pull/15075) * Quorum queues now support **strict priority queues** with per-priority message counts, correct redelivery ordering across priorities, and priority-aware message expiration scans. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) * Quorum queues now support **delayed retry** with configurable backoff based on delivery count. When messages are returned (via reject, nack, or modify), they can be held in a delayed state before becoming available again. The delay is based on delivery count: `min(min_delay * delivery_count, max_delay)`. Configuration is available via queue arguments (`x-delayed-retry-type`, `x-delayed-retry-min`, `x-delayed-retry-max`) or policy keys (`delayed-retry-type`, `delayed-retry-min`, `delayed-retry-max`). The retry type can be set to `disabled`, `all`, `failed`, or `returned`. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) * Quorum queues now support a configurable **consumer timeout**. When a consumer holds unacknowledged messages beyond the timeout, the messages are returned to the queue. For AMQP 1.0 clients, timed-out deliveries are released via `DISPOSITION(state=released)` instead of detaching the link, allowing the consumer to recover without re-attaching. MQTT consumers are also supported. The timeout can be set via the `x-consumer-timeout` consumer argument, queue argument, `consumer-timeout` policy key, or the global `consumer_timeout` setting in `rabbitmq.conf`. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) * A new `consumer_disconnected_timeout` setting controls how long quorum queues wait before returning messages when a consumer's node becomes unreachable due to a network partition. The default is 60 seconds. Configurable via `consumer_disconnected_timeout` in `rabbitmq.conf`, the `consumer-disconnected-timeout` policy key, or the `x-consumer-disconnected-timeout` queue argument. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) * Quorum queue **recovery snapshots** reduce recovery time after a member restart by avoiding the need to replay all enqueue commands from the log. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) * Quorum queue **snapshot throttling** now uses WAL fill ratio and reclaimable byte tracking to make smarter snapshotting decisions, yielding roughly one snapshot per queue per WAL cycle instead of excessive snapshots in shallow, fast-flowing queues. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) * Quorum queue **memory optimisations**: message references now use a compact packed integer representation ("compact" means up to 59-bit) when possible, **halving per-message memory overhead** in many scenarios. The `rabbit_fifo_index` module is no longer used by the main state machine. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) * Quorum queues now allow unlimited explicit message returns. The delivery limit is based on `delivery-count` rather than `acquired-count`, so messages can be explicitly returned to the queue without counting towards the delivery limit. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) * When quorum queue members (replicas) are deleted from a node, either manually via `rabbitmq-queues shrink` or as part of `rabbitmqctl forget_cluster_node`, the members are stopped in parallel. GitHub issue: [#15081](https://github.com/rabbitmq/rabbitmq-server/pull/15081) * Purging a quorum queue now also removes at-least-once dead-lettered messages that were pending delivery. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) #### Bug Fixes * If a quorum queue with a large backlog terminated abnormally, node memory footprint could spike. GitHub issue: [#15837](https://github.com/rabbitmq/rabbitmq-server/pull/15837) * `rabbitmqctl forget_cluster_node` now removes all quorum queue and stream members (replicas) before proceeding to leave the metadata store cluster. This order minimizes the risk of some replicas being left behind on the leaving node. GitHub issue: [#15729](https://github.com/rabbitmq/rabbitmq-server/pull/15729) * Quorum queue at-most-once dead lettering for the overflow behaviour `drop-head` now happens in the correct order. GitHub issue: [#14926](https://github.com/rabbitmq/rabbitmq-server/pull/14926) * Feature flag state in the registry and on disk were not consistent for a period of time during node boot. GitHub issue: [#14943](https://github.com/rabbitmq/rabbitmq-server/pull/14943) * Classic queues now implement AMQP 1.0 delivery-count and first-acquirer headers properly. GitHub issue: [#15020](https://github.com/rabbitmq/rabbitmq-server/pull/15020) ### Stream Plugin #### Bug Fixes * `stream.read_ahead` is a new setting that controls how much data is prefetched from disk for stream reads (consumption). GitHub issue: [#14948/](https://github.com/rabbitmq/rabbitmq-server/pull/14948) * Stream deletion is now more resilient and can handle certain mid-deletion failure scenarios. GitHub issue: [#14852](https://github.com/rabbitmq/rabbitmq-server/issues/14852) ### Grafana Dashboards #### Enhancements * The [dashboards](https://grafana.com/orgs/rabbitmq) were updated for the most recent RabbitMQ release series. ### Management Plugin #### Enhancements * `GET /api/queues/{vhost}` requests no longer perform unnecessary virtual host permission checks and log less (at `debug` level) as a result. GitHub issue: [#14923](https://github.com/rabbitmq/rabbitmq-server/discussions/14923) * Quorum queue delayed retry configuration and status, per-priority message counts, and consumer timeout state are now displayed in the management UI. GitHub issue: [#13885](https://github.com/rabbitmq/rabbitmq-server/pull/13885) * `GET /users/{user}/queues` has been added. GitHub issue: [#15074](https://github.com/rabbitmq/rabbitmq-server/pull/15074) ### MQTT Plugin #### Enhancements * For MQTT 5.0 publishers, when a message is rejected because the target queue's maximum length is exceeded, RabbitMQ now returns a `Quota exceeded` reason code in the PUBACK packet. This provides publishers with actionable information about why their message was rejected. GitHub issue: [#15075](https://github.com/rabbitmq/rabbitmq-server/pull/15075) ### Federation Plugin #### Enhancements * Federation links and their connections are now stopped in parallel. This significantly improves shutdown time for nodes with many (into thousands) federation links. GitHub issue: [#15271](https://github.com/rabbitmq/rabbitmq-server/pull/15271) * Federation links no longer restart during plugin or node shutdown. For nodes with hundreds or thousands of federation links, link recovery could significantly delay node shutdown. GitHub issue: [#15258](https://github.com/rabbitmq/rabbitmq-server/pull/15258) ### Shovel Plugin #### Enhancements * An optional `src-consumer-name` property can be specified to define the consumer tag (`amqp091` and `local` `src-protocol`) or link identifier (`amqp10` protocol) #### Bug Fixes * Improved target node resource alarm handling for AMQP 1.0 and local shovels. GitHub issue: [#14886](https://github.com/rabbitmq/rabbitmq-server/pull/14886) * Local shovels could run into an exception that would cause a shovel restart. GitHub issue: [#14872](https://github.com/rabbitmq/rabbitmq-server/pull/14872) * AMQP 1.0 shovels ignored the `sasl` URI parameter. GitHub issue: [#14867](https://github.com/rabbitmq/rabbitmq-server/pull/14867) ### OAuth 2 Plugin #### Bug Fixes * A usability improvement allows the plugin to automatically load the trusted system x.509 (TLS) certificates. GitHub issue: [#14927](https://github.com/rabbitmq/rabbitmq-server/pull/14927) ### LDAP Plugin #### Enhancements * LDAP queries, including multi-line ones, can now be specified in `rabbitmq.conf`. GitHub issue: [#14868](https://github.com/rabbitmq/rabbitmq-server/pull/14868) #### Bug Fixes * A usability improvement allows the plugin to automatically load the trusted system certificates when the user only enables TLS for the LDAP client but does not configure any other settings. GitHub issue: [#14937](https://github.com/rabbitmq/rabbitmq-server/pull/14937) ### HTTP Auth Backend Plugin #### Enhancements * The HTTP Auth Backend can now optionally provide a custom authorization denial reason to AMQP clients. To opt in, return `deny <Reason>` (instead of only `deny`) in the HTTP response body of your HTTP auth backend and set the following in your `rabbitmq.conf` file: ```ini auth_http.authorization_failure_disclosure = true ``` See the [README](https://github.com/rabbitmq/rabbitmq-server/blob/main/deps/rabbitmq_auth_backend_http/README.md) for more information. GitHub issue: [#14641](https://github.com/rabbitmq/rabbitmq-server/pull/14641) ### Tracing Plugin #### Bug Fixes * Trace file downloads now set the charset to UTF-8 when serving trace files. GitHub issue: [#13952](https://github.com/rabbitmq/rabbitmq-server/issues/13952) ### Dependency Changes * `ra` was upgraded from [`2.17.2`](https://github.com/rabbitmq/ra/releases/tag/v2.17.2) to [`3.1.2`](https://github.com/rabbitmq/ra/releases/tag/v3.1.2) * `osiris` was upgraded to [`1.3.0`](https://github.com/rabbitmq/osiris/releases) * `cuttlefish` was upgraded to [`3.6.0`](https://github.com/kyorai/cuttlefish/releases) * `gen_batch_server` was upgraded to [`0.9.2`](https://github.com/rabbitmq/gen-batch-server/releases) ## Source Code Archives To obtain source code of the entire distribution, please download the archive named `rabbitmq-server-4.3.0.tar.xz` instead of the source tarball produced by GitHub.

RabbitMQ 4.3.0-beta.1

RabbitMQ 4.2.5

RabbitMQ 4.1.8-rc.1

RabbitMQ 4.2.0-beta.4

RabbitMQ 4.2.0-beta.1

RabbitMQ 4.1.0

RabbitMQ 4.1.0-rc.2