Message enhancement rules are a configurable capability supported by the MQTT server. By setting rules, you can dynamically attach MQTT 5.0 properties to messages during publication based on configured conditions. These rules support flexible configuration and management through the console or TencentCloud API.
A message enhancement rule statement logically consists of two parts:
Conditions (Conditions): The conditions that trigger the rule, for example: when the message topic matches test/topic.
Actions (Actions): Operations performed when conditions are met, such as: adding Message Expiry Interval = 30 to the message.
Limitations and Constraints
Each cluster supports a maximum of 10 message enhancement rules. If you require additional quotas, please contact us.
Rules have priority settings, where a smaller priority value indicates a higher priority. The server executes rules in the order listed on the message enhancement rule page. Higher priority rules will override the actions of lower priority rules; if there is a conflict in rule configurations, the rule with higher priority takes precedence.
If the field content exceeds the length or size limitation after variable substitution, the server will automatically truncate the portion that exceeds the limit.
Configure Message Enhancement Rules
Creating Rules
1. Log in to the TDMQ for MQTT console > Cluster > Message Enhancement Rule, and click the Create rule button in the upper-left corner to configure message enhancement rules.
2. Fill in the basic information of the rule, matching conditions, and specific enhancement rule configurations based on actual circumstances. Refer to the filling instructions below for specific field filling. After filling, click Create Rule. If the "whether to enable this rule" option in the basic information was enabled during creation, the rule will take effect within 1 minute after creation; if not enabled during creation, it can also be enabled on the list page after the rule is created.
3. Successfully created rules can be viewed and managed on the list page; rules in the "Active" state cannot be deleted.
Rule Priority
1. Click the Adjust Priority button to modify the execution order of rules. The server will execute rules according to the current list order; if there is a conflict in rule configurations, the rule with higher priority takes precedence.
2. By dragging the
icon before each rule row, you can adjust the order.
Filling Instructions
Display Name
API Parameters
Description
Required
Example Value
Rule Name
RuleName
Set the rule name. It must comply with the naming rules: 3-64 characters, supporting Chinese characters, letters, numbers, "-", and "_".
Yes
"rule001"
Remarks
Remark
Set the rule description, which must not exceed 128 characters.
No
"Set expiration time"
Username
username
Enter a single username or a single resource expression. Supports the use of wildcards and rule variables, where "*" indicates support for all usernames.
Yes
"user*"
Client ID
clientId
Enter a single resource expression. Supports the use of wildcards and rule variables, where "*" indicates support for all clients.
Yes
"sensor*"
Topic
topic
Enter a single resource expression. Supports the use of wildcards and rule variables, where "*" indicates support for all Topics.
Yes
"home/room1/*"
Message Expiry Interval
messageExpiryInterval
Set the expiration time for messages in seconds. The value must be a positive integer within the range of 0–259200 seconds (0–72 hours), and 0 is not allowed.
No
3600 (indicating it expires after 1 hour)
Response Topic
responseTopic
Specify the response topic, which must be a valid UTF-8 string with a length not exceeding 256 characters. Wildcard characters "+" or "#" are not allowed. Supports the use of rule variable substitution.
No
"client/response/123"
Correlation Data
correlationData
The data field used to correlate requests and responses must be a valid UTF-8 string with a total size not exceeding 8KB. Supports the use of rule variable substitution.
No
"request-20251031"
User Properties
userProperty
Custom user attribute list; must be valid UTF-8 strings. Each attribute value (key-value pair) must not exceed 8KB in total size, with up to 10 user attributes allowed. Supports the use of rule variable substitution.
The username parameter supports the following wildcards:
Wildcard/Wildcard
Semantics
?
Any single character.
*
Any number of characters.
client ID
The clientId parameter supports the following wildcards:
Wildcard/Wildcard
Semantics
?
Any single character.
*
Any number of characters.
Topic
The topic parameter supports the following wildcards:
Wildcard/Wildcard
Semantics
+
Consistent with the MQTT protocol Topic Filter Wildcard.
#
Consistent with the MQTT protocol Topic Filter Wildcard.
?
Any single character.
*
Any number of characters.
Variable Substitution
Usage Instructions
Enter ${ in the input box to automatically display the system default rule variable substitution list.
Supported Parameters
Parameters that support rule variable substitution include:
topic
clientId
username
responseTopic
correlationData
userProperty
Note:
During rule execution, ${Variable} will be dynamically replaced with the corresponding real value; if the variable does not exist, it will be replaced with empty string. Please confirm the variable validity before use.
