Important changes

• For Docker images, the configuration directory /opt/emqx/etc has been removed from the VOLUME list, making it easier for users to rebuild images with changed configurations.
• CentOS 7 Erlang runtime rebuilt on OpenSSL-1.1.1n (previously 1.0), prior to v4.3.13, EMQX will fail to handshake and trigger malformed_handshake_data exception when clients use certain cipher suites.
• CentOS 8 Erlang runtime system rebuilt on RockyLinux 8. centos8 will remain in the package name for backward compatibility.

Enhancement

• Windows package support for building on Erlang/OTP 24.
• Add command line interface emqx_ctl pem_cache clean to allow forcibly clear x509 certificate cache to reload immediately after certificate file update.
• Refactored ExProto so that anonymous clients can also be displayed on Dashboard.
• Topic configuration items in bridges can now use ${node} placeholders.
• Add validation of UTF-8 strings in MQTT packets in strict mode. When set to true, invalid UTF-8 strings will cause the client to disconnect.
• MQTT-SN gateway supports initiative to synchronize registered topics after session resumed.
• Improve the writing precision of rule engine floating point data from 10 decimal places to 17 decimal places.
• EMQX will prompt how to modify the initial password of Dashboard at startup.

Bug fixes

• Fix the issue that the el8 installation package cannot be started on Amazon Linux 2022, the error content is errno=13 Permission denied.
• Fix an issue where the client could not reconnect if the connection process was blocked in some cases. Now waiting for more than 15 seconds without a response will force the old connection process to be closed.
• Fix the issue of query resource request timeout when rule engine resource is unavailable.
• Fix the issue of {error, eexist} error when re-run after hot upgrade failed.
• Fix an issue where publishing to a non-existing topic alias would crash the connection.
• Fix 500 error when querying LwM2M client list on another node via HTTP API.
• Fix HTTP API for subscribing topics crashes when invalid QoS are passed in.
• Fix the issue that the connection count was not updated because the related resources were not released when the connection process accessed through the ExProto exited abnormally.
• Fix an issue where the value of server_keepalive configuration item would be incorrectly applied to MQTT v3.1.1 clients.
• Fix Stomp client not firing $event/client_connection event messages.
• Fix the issue that the system memory alarm was incorrectly activated when EMQX was started.
• Fixed an issue where messages that failed to be delivered due to unregistered topics were not retransmitted when topics were successfully registered with the MQTT-SN client.
• Fix EMQX startup output error log when duplicate plugins are configured in loaded_plugins file.
• Fix MongoDB related features outputting excessive error logs when configured incorrectly.
• Add format check for Dashboard User and AppID, special characters such as / are not allowed.
• Corrected the reason code in the DISCONNECT packet returned when kicking the client to 0x98.
• Auto subscriptions will ignore empty topics.