MQTT Messaging Configuration

MQTT Messaging configuration allows you to specify settings for the MQTT protocol used by your EMQX Edge.

Example Configuration

mqtt = {
  max_packet_size = 1KB       # Maximum packet size EMQX Edge can accept and send, 1B~260MB.
  max_mqueue_len = 2048       # Maximum length of the in-flight window queue
  retry_interval = 10s        # Retry interval for QoS 1/2 message delivering
  keepalive_multiplier = 1.25 # Multiplier for MQTT keepalive timeout. 
  property_size = 32          # Maximum size for a MQTT user property.
}

Configuration Items

Configuration Item	Description	Value Range
max_packet_size	Specifies the maximum size of a packet that EMQX Edge can accept and send	1 Byte to 260 MB
max_mqueue_len	Specifies the maximum length of the in-flight window queue. Note: This item may affect the system performance and memory consumption. Please set it with caution.	1 ~ infinity
retry_interval	Specifies the retry interval for QoS 1/2 message delivering	1 ~ infinity
keepalive_multiplier	Specifies the multiplier for the MQTT keepalive timeout. The broker will disconnect the client if there's no activity for Keepalive * backoff time.	Float > 0.5
property_size	Specifies the maximum size for an MQTT user property.	1 ~ infinity

TIP

All of these MQTT configurations in EMQX Edge support hot upgrading. This means that any changes made to these settings will take effect immediately after you save the configuration file, without the need to restart the EMQX Edge.