Important changes:

• For Debian/Ubuntu users, Debian/Ubuntu package (deb) installed EMQ X now now run on systemd. This is to use systemd's supervision functionality to ensure that EMQ X service restarts after a crash. The package installation service upgrade from init.d to systemd has been verified, but it is still recommended that you verify and confirm again before deploying to the production environment, at least to ensure that systemd is available in your system

• MongoDB authentication supports DNS SRV and TXT Records resolution, which can seamlessly connect with MongoDB Altas

• Support dynamic modification of MQTT Keep Alive to adapt to different energy consumption strategies

Minor changes:

• Dashboard supports relative paths and custom access paths

• Supports configuring whether to forward retained messages with empty payload to suit users who are still using MQTT v3.1. The relevant configurable item is retainer.stop_publish_clear_msg

• Multi-language hook extension (ExHook) supports dynamic cancellation of subsequent forwarding of client messages

• Rule engine SQL supports the use of single quotes in FROM clause, for example: SELECT * FROM't/#'

• Change the default value of the max_topic_levels configurable item to 128. Previously, it had no limit (configured to 0), which may be a potential DoS threat

• Improve the error log content when the Proxy Protocol message is received but the proxy_protocol configuration is not turned on

• Add additional message attributes to the message reported by the gateway. Messages from gateways such as CoAP, LwM2M, Stomp, ExProto, etc., when converted to EMQ X messages, add fields such as protocol name, protocol version, user name, client IP, etc., which can be used for multi-language hook extension (ExHook)

• HTTP client performance improvement

• Add openssl-1.1 to RPM dependency

Bug fixes:

• Fix the issue that the client process becomes unresponsive due to the blockage of RPC calls between nodes

• Fix the issue that the lock management process ekka_locker crashes after killing the suspended lock owner

• Fix the issue that the Path parameter of WebHook action in rule engine cannot use the rule engine variable

• Fix MongoDB authentication module cannot use Replica Set mode and other issues

• Fix the issue of out-of-sequence message forwarding between clusters. The relevant configurable item is rpc.tcp_client_num

• Fix the issue of incorrect calculation of memory usage

• Fix MQTT bridge malfunction when remote host is unreachable (hangs the connection)

• Fix the issue that HTTP headers may be duplicated