Docs

Cloud Native Message Engine

Cluster configuration

MQTT configuration

On the Management > Cluster configuration > MQTT configuration page in the Dashboard, you can view or modify configuration items related to the MQTT protocol, including general configuration, session configuration, retained messages, and system topic configuration.

General

Under the General tab, the basic general configuration items for the MQTT protocol are displayed, including maximum packet size, maximum client ID length, topic hierarchy, and QoS configuration items.

Session

Under the Session tab, configuration items related to MQTT protocol sessions are displayed, including maximum subscription count, message retry interval, whether to store QoS 0 messages, and other related configurations.

Retained messages

Under the Retained messages tab, configuration items related to retained messages in the MQTT protocol are displayed, such as enabling retained messages, message storage type and method, maximum number of retained messages, retained message payload size, retained message expiration interval, and other related configurations.

Configuration items	Description
Enable retained messages	Whether to enable retained messages. tip When retained messages are disabled, existing retained messages will not be deleted.
Storage type	Storage type is fixed as built-in database.
Storage method	Retained message storage method. ram: Stored only in memory. disc: Stored in both memory and disk.
Maximum number of retained messages	The upper limit on the number of retained messages. The default is unlimited (0). After setting a limit for the maximum number of retained messages, MQTT will replace existing messages when the limit is reached, and you will not be able to store retained messages for new topics once the limit has been reached.
Maximum message payload size	The maximum payload size for retained messages. If the payload exceeds the maximum value, MQTT will treat the retained message as a regular message.
Message expiration interval	Expiration time for retained messages. By default, messages never expire (0). If the message expiration interval is set in the PUBLISH packet, the expiration time in the PUBLISH packet takes precedence.
Message cleanup interval	The interval for cleaning expired messages. Disabled by default.
Dispatch rate	Maximum dispatch rate for retained messages.

System topic

Under the System topic tab, configuration items related to MQTT built-in system topics are displayed, including message publishing interval, heartbeat interval, client connection/disconnection notifications, and other configuration items.

MQTT periodically publishes running status, usage statistics, and real-time client events to system topics starting with $SYS/. When a client subscribes to such topics, MQTT will publish the relevant information to that topic.

Last updated: 2026.01.26 16:22:16