emqx4.3/rel/config/examples/alarm.conf.example

## Alarm

alarm {
    ## The actions triggered when the alarm is activated
    ## Type: Array of the below enum
    ##   - log :: write the alarm to log
    ##   - publish :: publish the alarm as an MQTT message to the system topics
    actions = [log, publish]

    ## Maximum total number of deactivated alarms to keep as history
    ## Type: Range from 1 to 3000
    size_limit = 1000

    ## Retention time of deactivated alarms
    validity_period = 24h
}