RabbitMQ 4.3.4 is a maintenance release in the 4.3.x release series.

It is strongly recommended that you read 4.3.0 release notes
in detail if upgrading from a version prior to 4.3.0.

Minimum Supported Erlang Version

The minimum supported Erlang version for this release series is 27.0.

RabbitMQ and Erlang/OTP Compatibility Matrix 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.

Core Server

Bug Fixes

• Quorum queues in clusters upgraded from 3.13.x to 4.2.x and then to 4.3.x could stop
  emitting metrics and taking snapshots after a node restart.

  GitHub issues: #16974, #16990

• The AMQP 1.0 parser now detects standard message body sections more strictly.

  GitHub issue: #17017

• The AMQP 1.0 parser now decodes certain array values more efficiently.

  GitHub issue: #16994

Stream Plugin

Bug Fixes

• The single active consumer coordinator
  did not notify a consumer that was re-selected for activation while it was still deactivating,
  leaving the group without an active consumer.

  Contributed by @pterygota.

  GitHub issues: #16975, #16976

Management Plugin

Bug Fixes

• Very short lived exclusive queues could cause an exception during metric collection, producing
  log noise.

  GitHub issues: #16989, #16999, #17002

• After an IdP-initiated OAuth 2 login, the management UI now returns the user
  to the page that was open before the login instead of the default one.

  Contributed by @thisisnsh.

  GitHub issues: #16957, #16961

Enhancements

• The management UI Content Security Policy (CSP) no longer includes the unsafe-eval and
  unsafe-inline directives.

  GitHub issue: #16916

Federation Plugin

Bug Fixes

• In scenarios that involved a federated queue and a federated exchange with exactly the same name in the same virtual host,
  deleting an upstream unintentionally corrupted the federated exchange(s) operating state, breaking federation
  for the exchange in question.

  GitHub issues: #16991, #16997

Dependency Changes

None in this release.

RabbitMQ 4.2.9 is a maintenance release in the 4.2.x release series.

It is strongly recommended that you read 4.2.0 release notes
in detail if upgrading from a version prior to 4.2.0.

Minimum Supported Erlang Version

Important: starting with this release, the minimum supported Erlang version is 27.0. Erlang/OTP 26 has reached
end of life and is no longer supported.

GitHub issue: #16914

RabbitMQ and Erlang/OTP Compatibility Matrix 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.

Core Server

Bug Fixes

• Classic queue index directory paths could accumulate slashes, eventually failing
  with an enametoolong file system error.

  GitHub issue: #16833

• AMQP 1.0 management operations that declare an exchange with an alternate exchange now verify
  the necessary permissions on the alternate exchange, matching AMQP 0-9-1.

  GitHub issue: #16785

• AMQP 1.0 management GET /bindings operations now behave consistently with the rest
  of the binding-related handlers.

  GitHub issue: #16790

• Worker pool processes no longer terminate when they receive an unexpected message.

  Contributed by @Ayanda-D.

  GitHub issue: #16666

• A race condition between concurrent queue (or virtual host) deletion and a Ra cluster shutdown
  could log an exception.

  Contributed by @Ayanda-D.

  GitHub issue: #16880

• A closing channel (connection) that failed to send channel.close_ok on an already terminated
  writer or socket no longer produce log noise.

  Contributed by @Ayanda-D.

  GitHub issue: #16651

• Unexpected failures during channel termination cleanup no longer produce log noise.

  Contributed by @Ayanda-D.

  GitHub issue: #16740

• Code paths that use rabbit_queue_type_util:erpc_call/5 now handle more errors.

  Contributed by @Ayanda-D.

  GitHub issue: #16701

• Nodes could fail to start with a bad_generator exception in rabbit_queue_decorator:select/1
  when a quorum queue record in the metadata store had its decorators set to undefined.

  GitHub issues: #16843, #16844

• Enabling tracing on multiple virtual hosts concurrently could silently drop
  some of the virtual hosts from the traced set. All virtual host tracing state modifications
  are now linearized.

  GitHub issues: #16755, #16763

Enhancements

• Password salts are now generated using a cryptographically secure pseudo-random number generator (CSPRNG).

  GitHub issue: #16775

• Socket-level metric collection used by several protocol readers and the management agent
  now handles concurrently closed connections safely.

  Inspired by a contribution of @MugemaneBertin2001.

  GitHub issues: #16856, #16832

CLI Tools

Bug Fixes

• rabbitmq-plugins commands now tolerate plugins that are listed as enabled but are not installed.

  GitHub issue: #16896

• rabbitmq-plugins list no longer outputs an empty plugin table when the target node
  cannot be reached.

  GitHub issue: #16791

• rabbitmq-plugins commands now correctly handle file paths of remote nodes, validate remote nodes
  in offline mode, and no longer report false positives for rabbitmq-plugins is_enabled.

  GitHub issue: #16842

• Shell (Bash, zsh) command completion fixes.

  Contributed by @Chr1s70ph.

  GitHub issue: #16776

Enhancements

• rabbitmq-queues and rabbitmq-streams now provide transfer_leadership commands
  for individual queues and streams.

  GitHub issue: #16757

• rabbitmq-upgrade drain safety improvements: the command now handles certain failures
  more gracefully.

  Proposed by @MugemaneBertin2001.

  GitHub issues: #16865, #3369

Stream Plugin

Bug Fixes

• Permissions required for certain stream protocol operations were adjusted to be consistent
  with comparable operations over other protocols.

  GitHub issue: #16754

Enhancements

• The maximum number of super stream partitions is now limited to 1,000 partitions by default.
  This limit can be increased using the stream.max_super_stream_partitions key in rabbitmq.conf.

  GitHub issues: #16689, #16706

• A client RPC timeout is now logged as a concise message instead of an exception
  with a stack trace.

  Contributed by @MugemaneBertin2001.

  GitHub issues: #16829, #15744

Management Plugin

Bug Fixes

• OAuth 2 login could fail in Safari. A new token endpoint proxy is now used
  for the affected authorization flow.

  GitHub issues: #16664, #16892

• Several management UI templates now use safe string escaping in more places.

  GitHub issue: #16738, #16677

• HTTP API message publishing endpoint now uses a timeout when waiting for publisher confirms.

  GitHub issue: #16911

Enhancements

• Definition export over the HTTP API is now significantly more efficient and
  transfers the result using HTTP response streaming.

  GitHub issue: #16734

• The Referrer-Policy HTTP response header is now set (and configurable).

  GitHub issue: #16893

• HTTP API error responses were refactored to be more consistent and expose fewer internal details.

  GitHub issue: #16709

OAuth 2 AuthN and AuthZ Backend Plugin

Bug Fixes

• Fractional exp (token expiry) timestamp values are now honored.

  GitHub issue: #16713

Enhancements

• The token refresh path is now more robust.

  GitHub issue: #16858

Shovel Plugin

Bug Fixes

• Several shovel bug fixes, including one for static shovel URIs whose credentials
  could be logged.

  GitHub issues: #16855, #16835

• A shovel deleted before it successfully connected (in the starting state) no longer
  leaks its status entry.

  GitHub issue: #16767

Federation Plugin

Bug Fixes

• Federation upstream URIs are now validated more strictly.

  GitHub issue: #16942

MQTT Plugin

Enhancements

• More correct peer host detection in setups that have Proxy Protocol enabled.

  GitHub issue: #16933

Web MQTT Plugin

Enhancements

• More correct peer host detection in setups that have Proxy Protocol enabled.

  GitHub issue: #16933

• The HSTS response header policy can now be configured for Web MQTT listeners.

  GitHub issues: #14161, #16772

STOMP Plugin

Enhancements

• Internal socket handling refactoring shared by STOMP and Web STOMP connections.

  GitHub issue: #16935

Web STOMP Plugin

##...

RabbitMQ 4.3.3 is a maintenance release in the 4.3.x release series.

It is strongly recommended that you read 4.3.0 release notes
in detail if upgrading from a version prior to 4.3.0.

Minimum Supported Erlang Version

Important: starting with this release, the minimum supported Erlang version is 27.0. Erlang/OTP 26 has reached
end of life and is no longer supported.

GitHub issue: #16914

RabbitMQ and Erlang/OTP Compatibility Matrix 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.

Core Server

Bug Fixes

• Quorum queue, Khepri and other Raft leaders could optimistically commit new log entries in certain scenarios.

  GitHub issue: rabbitmq/ra#637

• Quorum queues that use at-least-once dead lettering could get their
  dead lettering process permanently stuck after repeated queue membership changes.

  GitHub issue: #16652

• Classic queue index directory paths could accumulate slashes, eventually failing
  with an enametoolong file system error.

  GitHub issue: #16833

• Enabling the tie_binding_to_dest_with_keep_while_cond feature flag could fail with an exception
  when certain exchange-to-exchange topologies.

  GitHub issue: #16824

• An invalid consumer_timeout value in the configuration now falls back to the default
  value (24 hours) instead of being used as is.

  GitHub issue: #16799

• AMQP 1.0 management operations that declare an exchange with an alternate exchange now verify
  the necessary permissions on the alternate exchange, matching AMQP 0-9-1.

  GitHub issue: #16785

• AMQP 1.0 management GET /bindings operations now behave consistently with the rest
  of the binding-related handlers.

  GitHub issue: #16790

• Worker pool processes no longer terminate when they receive an unexpected message.

  Contributed by @Ayanda-D.

  GitHub issue: #16666

• A race condition between concurrent queue (or virtual host) deletion and a Ra cluster shutdown
  could log an exception.

  Contributed by @Ayanda-D.

  GitHub issue: #16880

• A closing channel (connection) that failed to send channel.close_ok on an already terminated
  writer or socket no longer produce log noise.

  Contributed by @Ayanda-D.

  GitHub issue: #16651

• Unexpected failures during channel termination cleanup no longer produce log noise.

  Contributed by @Ayanda-D.

  GitHub issue: #16740

• Code paths that use rabbit_queue_type_util:erpc_call/5 now handle more errors.

  Contributed by @Ayanda-D.

  GitHub issue: #16701

• Nodes could fail to start with a bad_generator exception in rabbit_queue_decorator:select/1
  when a quorum queue record in the metadata store had its decorators set to undefined.

  GitHub issues: #16843, #16844

• Enabling tracing on multiple virtual hosts concurrently could silently drop
  some of the virtual hosts from the traced set. All virtual host tracing state modifications
  are now linearized.

  GitHub issues: #16755, #16763

Enhancements

• Password salts are now generated using a cryptographically secure pseudo-random number generator (CSPRNG).

  GitHub issue: #16775

• Socket-level metric collection used by several protocol readers and the management agent
  now handles concurrently closed connections safely.

  Inspired by a contribution of @MugemaneBertin2001.

  GitHub issues: #16856, #16832

CLI Tools

Bug Fixes

• rabbitmq-plugins commands now tolerate plugins that are listed as enabled but are not installed.

  GitHub issue: #16896

• rabbitmq-plugins list no longer outputs an empty plugin table when the target node
  cannot be reached.

  GitHub issue: #16791

• rabbitmq-plugins commands now correctly handle file paths of remote nodes, validate remote nodes
  in offline mode, and no longer report false positives for rabbitmq-plugins is_enabled.

  GitHub issue: #16842

• Shell (Bash, zsh) command completion fixes.

  Contributed by @Chr1s70ph.

  GitHub issue: #16776

Enhancements

• rabbitmq-queues and rabbitmq-streams now provide transfer_leadership commands
  for individual queues and streams.

  GitHub issue: #16757

• rabbitmq-upgrade drain safety improvements: the command now handles certain failures
  more gracefully.

  Proposed by @MugemaneBertin2001.

  GitHub issues: #16865, #3369

Stream Plugin

Bug Fixes

• Permissions required for certain stream protocol operations were adjusted to be consistent
  with comparable operations over other protocols.

  GitHub issue: #16754

Enhancements

• The maximum number of super stream partitions is now limited to 1,000 partitions by default.
  This limit can be increased using the stream.max_super_stream_partitions key in rabbitmq.conf.

  GitHub issues: #16689, #16706

• A client RPC timeout is now logged as a concise message instead of an exception
  with a stack trace.

  Contributed by @MugemaneBertin2001.

  GitHub issues: #16829, #15744

Management Plugin

Bug Fixes

• OAuth 2 login could fail in Safari. A new token endpoint proxy is now used
  for the affected authorization flow.

  GitHub issues: #16664, #16892

• Several management UI templates now use safe string escaping in more places.

  GitHub issue: #16738, #16677

• HTTP API message publishing endpoint now uses a timeout when waiting for publisher confirms.

  GitHub issue: #16911

Enhancements

• Definition export over the HTTP API is now significantly more efficient and
  transfers the result using HTTP response streaming.

  GitHub issue: #16734

• The Referrer-Policy HTTP response header is now set (and configurable).

  GitHub issue: #16893

• The Allow HTTP response header can now be excluded from HTTP API responses.

  GitHub issue: #16907

• HTTP API error responses were refactored to be more consistent and expose fewer internal details.

  GitHub issue: #16709

• HTTP access log entries for OAuth 2-authenticated requests now use the username determined
  by the authentication backend (e.g. preferred_username) instead of the client ID.

  GitHub issues: #16879, #16559

• Definition file uploads via the management UI now require a .json file extension
  (enabled via a feature switch).

  GitHub issue: #16946

OAuth 2 AuthN and AuthZ Backend Plugin

Bug Fixes

• Fractional exp (token expiry) timestamp values are now honored.

  GitHub issue: #16713

Enhancements

• The token refresh path is now more robust.

  GitHub issue: #16858

...

RabbitMQ 4.2.8 is a maintenance release in the 4.2.x release series.

It is strongly recommended that you read 4.2.0 release notes
in detail if upgrading from a version prior to 4.2.0.

Minimum Supported Erlang Version

RabbitMQ and Erlang/OTP Compatibility Matrix 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.

Core Server

Bug Fixes

• Users created without a password or a password hash (for example, those that rely on
  X.509 certificate-based authentication) over the HTTP API are now stored correctly,
  exactly like the users whose password was cleared with rabbitmqctl clear_password.

  GitHub issues: #16629, #16633

• Consumer activity status of classic queue consumers was not always correctly updated and reported
  when single active consumer was enabled.

  GitHub issues: #16532, #16450

• Default queue type (DQT) validation now treats empty strings the same way as a missing value: by falling back
  to the default (classic queues).

  GitHub issues: #16481, #16488

Enhancements

• The per-node channel limit (channel_max_per_node) is now also enforced for channels opened
  on direct Erlang client connections used by the Shovel and Federation plugins, matching the behavior
  enforced for "regular" AMQP 0-9-1 clients.

  GitHub issues: #16616, #16618

• Modules are now loaded in parallel early on node boot, reducing node startup time.

  GitHub issue: #16479

• Several new rabbitmq.conf keys now support encrypted values.

  GitHub issue: #16632

CLI Tools

Bug Fixes

• rabbitmqctl add_vhost now validates the provided default queue type value.

  GitHub issue: #16481

Stream Plugin

Bug Fixes

• Fixed a frame assembly performance regression in the stream protocol reader.

  GitHub issue: #16588

Enhancements

• Several stream protocol reader optimizations: stream metadata queries now contact cluster nodes concurrently,
  subscription lookups use a more efficient data structure, and frame processing short-circuits
  when a connection reaches a terminal state.

  GitHub issue: #16588

Management Plugin

Bug Fixes

• CORS hardening: access-control-request-headers values are now validated and
  a wildcard (*) origin header value is rejected.

  GitHub issue: #16544

• Definitions import now limits the size of multipart upload bodies, and definitions export
  download filenames are restricted to a safe character set.

  GitHub issue: #16544

• HTTP API 500 responses no longer include internal error details in the response body.

  GitHub issue: #16544

• Several HTTP response headers are now consistently lowercase, and a previously missing
  content-type header was added to certain responses.

  GitHub issue: #16544

Enhancements

• A one-time warning is now logged when the HSTS or CSP headers are disabled.

  GitHub issue: #16544

• The timestamp of the oldest message in a stream is now displayed on the stream page.

  GitHub issue: #15412

Prometheus Plugin

Enhancements

• More plugin configuration keys, such as prometheus.ssl.password, now support
  encrypted values in rabbitmq.conf.

  GitHub issues: #16516, #16521

MQTT Plugin

Bug Fixes

• mqtt.tcp_listen_options.* settings in rabbitmq.conf did not take effect
  due to a configuration translation issue.

  GitHub issue: #16529

Dependency Changes

• cuttlefish was upgraded to 3.9.1
• cowboy was upgraded to 2.16.0
• cowlib was upgraded to 2.17.0
• gun was upgraded to 2.4.0

RabbitMQ 4.3.2 is a maintenance release in the 4.3.x release series.

It is strongly recommended that you read 4.3.0 release notes
in detail if upgrading from a version prior to 4.3.0.

Minimum Supported Erlang Version

RabbitMQ and Erlang/OTP Compatibility Matrix 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.

Core Server

Bug Fixes

• Enabling the tie_binding_to_dest_with_keep_while_cond feature flag could fail in some
  rare cases.

  GitHub issue: #16587

• Users created without a password or a password hash (for example, those that rely on
  X.509 certificate-based authentication) over the HTTP API are now stored correctly,
  exactly like the users whose password was cleared with rabbitmqctl clear_password.

  GitHub issues: #16629, #16633

• Consumer activity status of classic queue consumers was not always correctly updated and reported
  when single active consumer was enabled.

  GitHub issues: #16532, #16450

• The values of the x-consumer-timeout and x-consumer-disconnected-timeout optional arguments
  are now validated at queue declaration time.

  GitHub issue: #16557

• Default queue type (DQT) validation now treats empty strings the same way as a missing value: by falling back.
  to the default (classic queues).

  GitHub issues: #16481, #16488

• Feature flag operations now avoid unnecessary work: flags that are already enabled on all cluster nodes
  are excluded from synchronization, and enabling an empty set of flags is a no-op.

  GitHub issue: #16497

• Configuration changes for deprecated features are now
  honored when possible.

  GitHub issue: #16500

Enhancements

• The per-node channel limit (channel_max_per_node) is now also enforced for channels opened
  on direct Erlang client connections used by the Shovel and Federation plugins, matching the behavior
  enforced for "regular" AMQP 0-9-1 clients.

  GitHub issues: #16616, #16618

• Modules are now loaded in parallel early on node boot, reducing node startup time.

  GitHub issue: #16479

• Several new rabbitmq.conf keys now supports encrypted values.

  GitHub issue: #16632

CLI Tools

Bug Fixes

• rabbitmqctl set_topic_permissions now validates target user and exchange for existence.

  GitHub issue: #16590

• rabbitmqctl add_vhost now validates the provided default queue type value.

  GitHub issue: #16481

Stream Plugin

Bug Fixes

• Fixed a frame assembly performance regression in the stream protocol reader.

  GitHub issue: #16588

Enhancements

• Several stream protocol reader optimizations: stream metadata queries now contact cluster nodes concurrently,
  subscription lookups use a more efficient data structure, and frame processing short-circuits
  when a connection reaches a terminal state.

  GitHub issue: #16588

Management Plugin

Bug Fixes

• CORS hardening: access-control-request-headers values are now validated and
  a wildcard (*) origin header value is rejected.

  GitHub issue: #16544

• Definitions import now limits the size of multipart upload bodies, and definitions export
  download filenames are restricted to a safe character set.

  GitHub issue: #16544

• HTTP API 500 responses no longer include internal error details in the response body.

  GitHub issue: #16544

• Several HTTP response headers are now consistently lowercase, and a previously missing
  content-type header was added to certain responses.

  GitHub issue: #16544

Enhancements

• A one-time warning is now logged when the HSTS or CSP headers are disabled.

  GitHub issue: #16544

• The timestamp of the oldest message in a stream is now displayed on the stream page.

  GitHub issue: #15412

• The queue list page can now display a "Delayed" message count column, for example, for
  quorum queues that have a retry policy configured.

  GitHub issue: #16639

Prometheus Plugin

Enhancements

• More plugin configuration keys, such as prometheus.ssl.password, now support
  encrypted values in rabbitmq.conf.

  GitHub issues: #16516, #16521

MQTT Plugin

Bug Fixes

• mqtt.tcp_listen_options.* settings in rabbitmq.conf did not take effect
  due to a configuration translation issue.

  GitHub issue: #16529

Dependency Changes

• cuttlefish was upgraded to 3.9.1
• cowboy was upgraded to 2.16.0
• cowlib was upgraded to 2.17.0
• gun was upgraded to 2.4.0

RabbitMQ 4.3.1 is a maintenance release in the 4.3.x release series.

It is strongly recommended that you read 4.3.0 release notes
in detail if upgrading from a version prior to 4.3.0.

Minimum Supported Erlang Version

RabbitMQ and Erlang/OTP Compatibility Matrix 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.

Core Server

Bug Fixes

• If a queue was bound to a topic exchange using an empty binding key (""),
  messages published to any topic exchange with an empty
  routing key would be incorrectly routed to that queue.

  To apply the fix, enable the new topic_binding_projection_v5 feature flag after upgrading all cluster nodes.

  GitHub issue: #16271

• A virtual host could be falsely considered to be deleted in certain metadata store error and timeout scenarios.

  GitHub issue: #16422

• Passive queue and exchange declarations are now allowed for users that have any permission
  on the virtual host (configure, write, or read), not only configure.

  GitHub issues: #16272, #16085

• Classic queue shared message store GC could fall behind other queue activity under heavy load

  GitHub issues: #16142, #16141

• Classic queue message store: garbage collection is now stopped cleanly during node shutdown.

  GitHub issue: #15498

• Quorum queues now gracefully handle negative priority values.

  GitHub issue: #16280

• Quorum queues: delayed retry-related policy keys are now accepted in policy definitions.

  GitHub issues: #16395, #16398

• Fixed a bug where quorum queue's at-least-once dead lettering could direct commands to
  the wrong member (replica).

  GitHub issue: #16203

• Quorum queues: reintroduced Raft WAL max entries default of 500K.

  GitHub issue: #16382

• A quorum queue could crash during recovery after an unclean shutdown

  PR: rabbitmq/ra#629

• Stream queue argument validation was improved.

  GitHub issue: #16285

Enhancements

• channel_max was renamed to max_channels in rabbitmq.conf. The original name is
  still supported as an alias.

  GitHub issue: #16347

• connection_max was renamed to max_connections in rabbitmq.conf. The original name is
  still supported as an alias.

  GitHub issue: #16347

• The per-node max_connections limit is now enforced for AMQP 1.0 connections as well as AMQP 0-9-1 ones.

  GitHub issue: #16300

• When a plain-text client connects to a TLS listener (or vice versa) for
  AMQP 0-9-1, MQTT, STOMP, and the Stream protocol, target node will log a more useful message.

  GitHub issues: #16342, #16344

• The permission cache is now traversed less often during AMQP 1.0 management and AMQP 0-9-1 channel checks.

  GitHub issue: #16274

Stream Plugin

Bug Fixes

• Stream protocol: an open frame with empty properties is now handled correctly.

  GitHub issue: #16341

Enhancements

• It is now possible to cap the maximum number of concurrent Stream Protocol client
  connections using the stream.max_connections configuration key in rabbitmq.conf.

  GitHub issue: #16341

Management Plugin

Bug Fixes

• HTTP API GET /api/connections could return a 500 response when STOMP connections were present.

  GitHub issue: #16435

Enhancements

• It is now possible to cap the maximum number of concurrent HTTP API connections using the management.tcp.max_connections,
  management.ssl.max_connections configuration keys in rabbitmq.conf.

  GitHub issue: #16407

• The peer (client) certificate serial number is now exposed in the management UI and select CLI commands.

  GitHub issue: #16463

Prometheus Plugin

Enhancements

• It is now possible to cap the maximum number of concurrent HTTP API connections using the prometheus.tcp.max_connections,
  prometheus.ssl.max_connections configuration keys in rabbitmq.conf.

  GitHub issue: #16407

MQTT Plugin

Bug Fixes

• The MQTT connection process no longer fails and logs an exception when keepalive checks encounter socket errors on
  an already-closed connection.

  GitHub issue: #16391

Enhancements

• It is now possible to cap the maximum number of concurrent MQTT client connections using the mqtt.max_connections
  configuration key in rabbitmq.conf.

  GitHub issue: #16367

Federation Plugin

Bug Fixes

• Federation links could fail to start during rolling cluster restarts.

  GitHub issues: #16234, #16224

LDAP Plugin

Enhancements

• New rabbitmq.conf configuration settings for TLS cipher suites: auth_ldap.ssl_options.ciphers.*.

  GitHub issue: #16226

HTTP Auth Backend Plugin

Enhancements

• New rabbitmq.conf configuration settings for TLS cipher suites: auth_http.ssl_options.ciphers.*.

  GitHub issue: #16226

Auth Backend Cache Plugin

Bug Fixes

• The cache was not effective for reconnecting clients.

  GitHub issues: #16255, #16258

Trust Store Plugin

Bug Fixes

• A user-provided fail_if_no_peer_cert value in the plugin's TLS options is now respected. Previously,
  an internal default could override the configured value.

  GitHub issue: #16201

Enhancements

• New rabbitmq.conf configuration settings for TLS cipher suites: trust_store.ssl_options.ciphers.*.

  GitHub issue: #16226

Dependency Changes

• ra was upgraded to 3.1.7
• cuttlefish was upgraded to 3.7.0
• cowboy was upgraded to 2.15.0
• cowlib was upgraded to 2.16.1
• gun was upgraded to 2.3.0

RabbitMQ 4.2.7 is a maintenance release in the 4.2.x release series.

It is strongly recommended that you read 4.2.0 release notes
in detail if upgrading from a version prior to 4.2.0.

Minimum Supported Erlang Version

RabbitMQ and Erlang/OTP Compatibility Matrix 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.

Core Server

Bug Fixes

• A virtual host could be falsely considered to be deleted in certain metadata store error and timeout scenarios.

  GitHub issue: #16422

• Passive queue and exchange declarations are now allowed for users that have any permission
  on the virtual host (configure, write, or read), not only configure.

  GitHub issue: #16272

• Classic queue message store: garbage collection is now stopped cleanly during node shutdown.

  GitHub issue: #15498

• Fixed a bug where quorum queue's at-least-once dead lettering could direct commands to
  the wrong member (replica).

  GitHub issue: #16203

• Stream queue argument validation was improved.

  GitHub issue: #16285

Enhancements

• channel_max was renamed to max_channels in rabbitmq.conf. The original name is
  still supported as an alias.

  GitHub issue: #16347

• connection_max was renamed to max_connections in rabbitmq.conf. The original name is
  still supported as an alias.

  GitHub issue: #16347

• The per-node max_connections limit is now enforced for AMQP 1.0 connections as well as AMQP 0-9-1 ones.

  GitHub issue: #16300

• The permission cache is now traversed less often during AMQP 1.0 management and AMQP 0-9-1 channel checks.

  GitHub issue: #16274

Stream Plugin

Bug Fixes

• Stream protocol: an open frame with empty properties is now handled correctly.

  GitHub issue: #16341

Enhancements

• It is now possible to cap the maximum number of concurrent Stream Protocol client
  connections using the stream.max_connections configuration key in rabbitmq.conf.

  GitHub issue: #16341

Management Plugin

Bug Fixes

• HTTP API GET /api/connections could return a 500 response when STOMP connections were present.

  GitHub issue: #16435

Enhancements

• It is now possible to cap the maximum number of concurrent HTTP API connections using the management.tcp.max_connections,
  management.ssl.max_connections configuration keys in rabbitmq.conf.

  GitHub issue: #16407

• The peer (client) certificate serial number is now exposed in the management UI and select CLI commands.

  GitHub issue: #16463

Prometheus Plugin

Enhancements

• It is now possible to cap the maximum number of concurrent HTTP API connections using the prometheus.tcp.max_connections,
  prometheus.ssl.max_connections configuration keys in rabbitmq.conf.

  GitHub issue: #16407

MQTT Plugin

Bug Fixes

• The MQTT connection process no longer fails and logs an exception when keepalive checks encounter socket errors on
  an already-closed connection.

  GitHub issue: #16391

Enhancements

• It is now possible to cap the maximum number of concurrent MQTT client connections using the mqtt.max_connections
  configuration key in rabbitmq.conf.

  GitHub issue: #16367

Federation Plugin

Bug Fixes

• Federation links could fail to start during rolling cluster restarts.

  GitHub issues: #16234, #16224

LDAP Plugin

Enhancements

• New rabbitmq.conf configuration settings for TLS cipher suites: auth_ldap.ssl_options.ciphers.*.

  GitHub issue: #16226

HTTP Auth Backend Plugin

Enhancements

• New rabbitmq.conf configuration settings for TLS cipher suites: auth_http.ssl_options.ciphers.*.

  GitHub issue: #16226

Auth Backend Cache Plugin

Bug Fixes

• The cache was not effective for reconnecting clients.

  GitHub issues: #16255, #16258

Trust Store Plugin

Bug Fixes

• A user-provided fail_if_no_peer_cert value in the plugin's TLS options is now respected. Previously,
  an internal default could override the configured value.

  GitHub issue: #16201

Enhancements

• New rabbitmq.conf configuration settings for TLS cipher suites: trust_store.ssl_options.ciphers.*.

  GitHub issue: #16226

Dependency Changes

• ra was upgraded to 2.17.3
• cuttlefish was upgraded to 3.7.0
• cowboy was upgraded to 2.15.0
• cowlib was upgraded to 2.16.1
• gun was upgraded to 2.3.0

RabbitMQ 4.3.0 is 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, this
won't be a breaking change for nearly all instalations but it will affect community
plugins that use Mnesia.

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

Team RabbitMQ recommends removing the above keys from rabbitmq.conf before or shortly after upgrading.

Deprecated Features are Now Disabled by Default

A number of deprecated features are now disabled
by default and require the user to opt-in in order to use them.

This includes non-durable (transient) non-exclusive queues:
attempts to declare a queue with such property combination will be rejected by default.
Use durable queues, transient exclusive queues, or durable queues with a queue TTL instead.

To explicitly allow transient non-exclusive queues, make sure that
all nodes in the cluster include the following rabbitmq.conf key
and were restarted so that all nodes have a consistent view of the deprecated
feature settings:

# Enables deprecated non-durable (transient) non-exclusive queues
# (disabled by default as of RabbitMQ `4.3.0`, will be removed in a later version).
#
# Must be effective on all cluster nodes BEFORE
# the cluster is upgraded to `4.3.0`.
# If only some nodes have the setting configured, it will not have the desired effect.
deprecated_features.permit.transient_nonexcl_queues = true

If only some nodes have setting configured, it will not have the desired effect.

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 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 for 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 largely avoid the need for
such as feature.

Release Highlights

Khepri is Now The Only Metadata Store

As of this release, Khepri is the only 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 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 for documentation on upgrades and GitHub 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 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

• 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

• 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

• 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

• 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

• 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

• 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](ht...

RabbitMQ 4.2.6 is a maintenance release in the 4.2.x release series.

It is strongly recommended that you read 4.2.0 release notes
in detail if upgrading from a version prior to 4.2.0.

Minimum Supported Erlang Version

RabbitMQ and Erlang/OTP Compatibility Matrix 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.

Core Server

Bug Fixes

• Quorum queues: get_checked_out aux command could return messages in incorrect order

  GitHub issue: #16008

• 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

• The channel limit exceeded error message now correctly identifies the per-user limit
  as the reason

  GitHub issue: #15750

• AMQP 0-9-1: configure permission checks now apply to passive queue and exchange declarations,
  matching the behavior of their regular counterparts

• Khepri: missing keys are now correctly distinguished from errors in certain internal operations,
  avoiding spurious error-level log messages

  GitHub issue: #15942

• Bindings targeting Direct Reply-to pseudo-queues are now rejected instead of
  being silently accepted without any functional effect

  GitHub issue: #15935

Enhancements

• More rabbitmq.conf keys now accept tagged values (e.g., encrypted:...)

  GitHub issue: #15808

• 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

• AMQP 0-9-1: configure permission checks now apply to passive queue and exchange declarations,
  matching the behavior of their regular counterparts

  GitHub issue: #16085

• AMQP 0-9-1: when a connection's credentials are refreshed, the permissions cache is now
  cleared and consumer permissions are re-validated immediately

  GitHub issue: #16092

Management Plugin

Bug Fixes

• effective_policy_definition in HTTP API responses now returns an empty JSON object
  (not an array or empty string) when no policy applies to a queue

  GitHub issue: #16017

• Management UI: OAuth 2 combined with basic_auth could fail to reload provider
  configuration correctly

  GitHub issue: #15858

• Management UI: preference cookie expiry now respects the configured session timeout
  setting rather than using a hardcoded value

  GitHub issue: #15814

• Management UI: users were presented with a 401 error after changing their own password
  via the UI. The session is now refreshed automatically

  GitHub issue: #15730

• The deprecated, unused GET /api/auth endpoint was removed

  It has been out of use since 3.11 but never removed.

  GitHub issue: #16083

• POST /api/users/bulk-delete now respects the protected_users configuration,
  matching the behavior of the single-user DELETE /api/users/:name endpoint

  GitHub issue: #16143

• Quorum queue status and stream tracking endpoints now enforce virtual host
  access checks, consistent with all other vhost-scoped endpoints

  GitHub issue: #16104

Enhancements

• HTTP API displays static connection info (peer address, TLS details, auth mechanism)
  even when stats collection is disabled via rabbitmq.conf

  GitHub issue: #16009

• Super stream creation via HTTP API now verifies configure permission, matching
  the stream protocol code path

  GitHub issue: #16099

• Management API regex filters (?name=...&use_regex=true) now enforce match limits,
  preventing pathological patterns from consuming excessive CPU time

  GitHub issue: #16074

MQTT Plugin

Bug Fixes

• Fixed a timing-sensitive issue around Last Will message delivery and session expiration

  GitHub issue: #15999

Enhancements

• MQTT QoS 0 queue type now reports member information in management API responses

  GitHub issue: #15656

Web MQTT Plugin

Enhancements

• A default max_frame_size is now set on WebSocket connections, bounding decompressed frame sizes.
  The limit starts at mqtt.max_packet_size_unauthenticated and is raised after successful CONNECT

  GitHub issue: #16180

• A login_timeout is now enforced for WebSocket connections, matching the TCP listener behavior

  GitHub issue: #16120

• WebSocket Origin header validation is now available via web_mqtt.allow_origins

  GitHub issue: #16158

Web STOMP Plugin

Enhancements

• A default max_frame_size is now set on WebSocket connections. A smaller pre-authentication
  limit is raised after successful STOMP CONNECT, matching the Web MQTT pattern

  GitHub issue: #16180

• A login_timeout is now enforced for WebSocket connections, matching the TCP listener behavior

  GitHub issue: #16120

• WebSocket Origin header validation is now available via web_stomp.allow_origins

  GitHub issue: #16158

Shovel Plugin

Bug Fixes

• AMQP 1.0 shovels now properly detach links when closing connections, preventing
  spurious error log entries during shutdown

  GitHub issue: #15603

• AMQP 1.0 shovel status no longer includes full connection URIs in API responses
  and CLI output

  GitHub issue: #16108

Shovel Management Plugin

Bug Fixes

• DELETE operations now require the policymaker tag, matching the
  federation plugin counterpart

  GitHub issue: #16051

Federation Management Plugin

Bug Fixes

• Federation link restart operations now require the policymaker tag

  GitHub issue: #16051

OAuth 2 Plugin

Bug Fixes

• The auth cache backend now correctly delegates token expiry timestamps to the wrapped backend,
  ensuring connections are closed when tokens expire

  GitHub issue: #16100

• OAuth 2 management UI: improved provider configuration loading and rendering

  GitHub issue: #15858

LDAP Plugin

Bug Fixes

• DN values are now handled per RFC 4514

  GitHub issue: #16101

Trust Store Plugin

Enhancements

• Refactored certificate identification to avoid (unlikely) conflicts

  GitHub issue: #16116

• Proper CLI commands for trust store certificate management have been introduced

  GitHub issue: #15746

• Rejected certificates are now logged with additional diagnostic details

  GitHub issue: #15889

Consistent Hashing Exchange Plugin

Bug Fixes

• Binding weights above 10,000 are now rejected. Previously, extremely large weights could cause
  excessive memory allocation

  GitHub issue: #16118

Dependency Changes

• khepri was upgraded to 0.17.7
• gen_batch_server was upgraded to 0.9.1

RabbitMQ 4.3.0-rc.1 is a new feature release candidate.

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, this
won't be a breaking change for nearly all instalations but it will affect community
plugins that use Mnesia.

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

Team RabbitMQ recommends removing the above keys from rabbitmq.conf before or shortly after upgrading.

Deprecated Features are Now Disabled by Default

A number of deprecated features are now disabled
by default and require the user to opt-in in order to use them.

This includes non-durable (transient) non-exclusive queues:
attempts to declare a queue with such property combination will be rejected by default.

Use durable queues or transient exclusive queues instead.

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 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 for 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 largely avoid the need for
such as feature.

Release Highlights

Khepri is Now The Only Metadata Store

As of this release, Khepri is the only 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 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 for documentation on upgrades and GitHub 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 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

• 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

• 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

• 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

• 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

• 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

• 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

• 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

• 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

• The `x-mod...