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

##--------------------------------------------------------------------
## Retainer
##
## Configuration related to handling PUBLISH packets with a retain flag set to 1
##--------------------------------------------------------------------

retainer {
    ## Message retention time, default is 0 means the message will never expire
    msg_expiry_interval = 5s

    ## Maximum message size allowed
    max_payload_size = 1MB

    ## When the retained flag of the PUBLISH message is set and Payload is empty, whether to continue to publish the message
    stop_publish_clear_msg = false

    ## Maximum retained messages delivery rate per session
    delivery_rate = "1000/s"

    ## Retained messages store backend
    backend {
      ## Built-in database (Mnesia)
      type = built_in_database

      ## Specifies whether the messages are stored in RAM or persisted on disk
      ## Type: enum: ram | disc
      storage_type = ram

      ## Maximum number of retained messages. 0 means no limit
      max_retained_messages = 0
     }
 }