Project: EMQ Technologies (App Definition and Development / Streaming & Messaging)
File: v5.4.0.en.md

Stop releasing packages for Windows. Stop releasing packages for MacOS 11 (BigSur). Stop supporting UDP multicast based clustering strategy. Fix topic-filter overlapping handling in shared subscription. Hook callback `session.subscribed` and `client.subscribe` will now receive shared subscription in its full representation, e.g. `$share/group1/topic1/#`, and the `share` property is deleted from `subopts`. Hook callback `session.unsubscribed` and `client.unsubscribe` will now receive shared subscription in its full representation, e.g. `$share/group1/topic1/#` instead of just `topic1/#`. ExHook Proto changed. The `share` field in message `SubOpts` was deprecated. ExHook Server will now receive shared subscription in its full representation, e.g. `$share/group1/topic1/#`, and the `share` property is deleted from message `SubOpts`. `session.subscribed` and `session.unsubscribed` rule-engine events will have shared subscriptions in their full representation for `topic`, e.g. `$share/group1/topic1/#` instead of just `topic1/#`. Modified the Prometheus API and configuration to implement the following improvements: Restructured configuration sections to group related settings, improving readability and maintainability. Introduced `enablebasicauth` configuration for basic authentication on the scrape API endpoint, enhancing security. Maintained backwards compatibility while refactoring code, avoiding breaking changes. Introduced an enhancement for configuring sensitive authentication fields in bridges, such as passwords, tokens, and secret keys. This improvement allows the use of secrets stored as files in the file system. These secrets can be securely referenced in configuration files using the special `file://` prefix, enhancing the security of sensitive data handling in bridge configurations. Introduced Open Telemetry Logs Handler that allows to format log events in alignment with the Open Telemetry log data model. This handler facilitates the exportation of formatted log events to a configured Open Telemetry collector or back-end, thereby enhancing log management and integration capabilities. Switched to the new `v2` routing store schema by default. New schema improves both subscription and routing performance, especially in scenarios with concurrent subscriptions to topic filters sharing common wildcard prefixes. However, it does come with a minor increase in memory usage. This schema also eliminates the need for a separate index, thus inconsistencies in the routing state rarely encountered in previous versions should no longer be possible. If a cluster is rolling upgraded from older version, the cluster will continue to use `v1` store until a full cluster (non-rolling) restart happens. Users can still opt for the previous schema by configuring the `broker.routing.storage_schema` option to `v1`. However, this also requires a complete, non-rolling restart of the cluster to take

Implemented Open Telemetry distributed tracing feature. Implemented a dedicated HTTP API for the import and export of configuration and user data. Upgraded QUIC protocol stack. Implemented a preliminary Role-Based Access Control for the REST API. In this version, there are three predefined roles: Administrator: This role can access all resources. Viewer: This role can only view resources and data, corresponding to all GET requests in the REST API. Publisher: Specifically tailored for MQTT message publishing, this role is confined to accessing endpoints related to message publication. Support hot update of TCP/SSL/WS/WSS MQTT listeners configuration. This allows changing most of the configuration parameters without restarting the listener and disconnecting the clients. The limitations are: For TCP/SSL listeners, changes to the following parameters still require listener restart and clients reconnect: `bind` `tcp_options.backlog` For WS/WSS (WebSocket) listeners, changing transport related parameters (listed below) will cause listening socket to be re-opened, but established connections will stay uninterrupted. `bind` `tcp_options.` `ssl_options.` Fixed COAP gateway bug that caused it to ignore subscription options. Upgraded grpc-erl to 0.6.12. This update addresses a potential deadlock issue where the grpc client started dependent apps lazily. Updated `gen_rpc` library to version 3.3.1. The new version includes several performance improvements: Avoiding allocating extra memory for the packets before they are sent to the wire in some cases. Bypassing network for the local calls. Avoid senstive data leaking in debug logs Fixed an issue when API tokens were sometimes unavailable immediately after login due to race condition. Fixed an issue where nodes in the cluster would occasionally return a stale view when updating configurations on different nodes concurrently. Fixed an issue when the rule engine cannot connect to Redis hosted by Upstash. Before the fix, after establishing a TCP connection with the Redis service, the Redis driver of EMQX used to send AUTH and SELECT commands. However, the `upstash` Redis service does not support Inline Commands, which causes the rule engine to fail to connect to the `upstash` Redis service. After the fix, the Redis driver of EMQX uses RESP (REdis Serialization Protocol) to send AUTH and SELECT commands. Always acknowledge `DISCONNECT` packet to MQTT-SN client regardless of whether the connection has been successfully established before. Fix an issue where DTLS enabled MQTT-SN gateways could not be started, caused by incompatibility of default listener configuration with the DTLS implementation.