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

## MQTT protocol related settings
## Settings in this section is applied globally to all MQTT connections/sessions in this node

mqtt {
    ## After the TCP connection is established,
    ## if the MQTT CONNECT packet from the client is not received within the time specified by idle_timeout, the connection will be disconnected
    ## Type:
    ##   - infinity :: Never disconnect
    ##   - Time Duration :: The idle time
    idle_timeout = 15s

    ## Maximum MQTT packet size allowed
    max_packet_size = 1MB

    ## Maximum allowed length of MQTT Client ID
    ## Type: Rnage from 23 to 65535
    max_clientid_len = 65535

    ## Maximum topic levels allowed
    ## Type: Range from 1 to 65535
    max_topic_levels = 128

    ## Maximum QoS allowed
    max_qos_allowed = 2

    ## Maximum topic alias, 0 means no topic alias supported
    ## Type: Range from 0 to 65535
    max_topic_alias = 65535

    ## Whether to enable support for MQTT retained message
    retain_available = true

    ## Whether to enable support for MQTT wildcard subscription
    wildcard_subscription = true

    ## Whether to enable support for MQTT shared subscription
    shared_subscription = true

    ## Whether to enable support for MQTT exclusive subscription
    exclusive_subscription = false

    ## Ignore loop delivery of messages for MQTT v3.1.1/v3.1.0, similar to No Local subscription option in MQTT 5.0
    ignore_loop_deliver = false

    ## Parse MQTT messages in strict mode.
    ## When set to true, invalid utf8 strings in for example client ID, topic name, etc. will cause the client to be disconnected
    strict_mode = false

    ## Specify the response information returned to the client
    response_information  = ""

    ## The keep alive that EMQX requires the client to use
    ## Type:
    ##   - disabled :: the keep alive specified by the client will be used
    ##   - Integer :: Keepalive time, only applicable to clients using MQTT 5.0 protocol
    server_keepalive = disabled

    ## Keep-Alive Timeout = Keep-Alive interval × Keep-Alive Multiplier
    keepalive_multiplier = 1.5

    ## Maximum number of subscriptions allowed per client
    ## Type: infinity | Integer
    max_subscriptions = infinity

    ## Force upgrade of QoS level according to subscription
    upgrade_qos = false

    ## Maximum number of QoS 1 and QoS 2 messages that are allowed to be delivered simultaneously before completing the acknowledgment
    ## Type: Range from 1 to 65535
    max_inflight = 32

    ## Retry interval for QoS 1/2 message delivering
    retry_interval = 30s

    ## For each publisher session, the maximum number of outstanding QoS 2 messages pending on the client to send PUBREL
    ## Type: infinity | Integer
    max_awaiting_rel = 100

    ## For client to broker QoS 2 message, the time limit for the broker to wait before the PUBREL message is received
    await_rel_timeout = 300s

    ## Specifies how long the session will expire after the connection is disconnected, only for non-MQTT 5.0 connections
    session_expiry_interval = 2h

    ## Maximum queue length. Enqueued messages when persistent client disconnected, or inflight window is full
    ## Type: infinity | Integer
    max_mqueue_len = 1000

    ## Specifies whether to store QoS 0 messages in the message queue while the connection is down but the session remains
    mqueue_store_qos0 = true

    ## Whether to user Client ID as Username
    use_username_as_clientid = false

    ## Use the CN, DN field in the peer certificate or the entire certificate content as Username
    ## Type:
    ##   - disabled
    ##   - cn :: CN field of the certificate
    ##   - dn :: DN field of the certificate
    ##   - crt :: the content of the DER or PEM certificate
    ##   - pem :: PEM format content converted from DER certificate content
    ##   - md5 :: the MD5 value of the content of the DER or PEM certificate
    peer_cert_as_username = disabled

    ## Use the CN, DN field in the peer certificate or the entire certificate content as Client ID
    ## Type: See the above
    peer_cert_as_clientid = disabled

    ## Dispatch strategy for shared subscription
    ## Type:
    ##   - random :: dispatch the message to a random selected subscriber
    ##   - round_robin :: select the subscribers in a round-robin manner
    ##   - round_robin_per_group :: select the subscribers in round-robin fashion within each shared subscriber group
    ##   - local :: select random local subscriber otherwise select random cluster-wide
    ##   - sticky :: always use the last selected subscriber to dispatch, until the subscriber disconnects.
    ##   - hash_clientid :: select the subscribers by hashing the `clientIds`
    ##   - hash_topic :: select the subscribers by hashing the source topic"""
    shared_subscription_strategy = round_robin
}