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Rate Limit ​

EMQX allows for specifying limits on connection speed and messaging speed, using a backpressure scheme that avoids system overload at the entry point and guarantees system stability with predictable throughput.

Listener-Level Limiters ​

Limiters can operate at the listener level. EMQX uses the following types of limiters to specify the rate limits:

TypeDashboard UIDescriptionPost-Overload Behavior
bytes_rateMax Message Publishing Traffic (Per Client)The size of messages in bytes published per second by a single clientPause receiving client messages
bytes_burstMax Message Publishing Traffic Burst (Per Client)Number of bytes that can be sent in a burst by a single client, based on the regular Data Publishing Rate.Pause receiving client messages
messages_rateMax Message Publishing Rate (Per Client)The number of messages published per second by a single clientPause receiving client messages
messages_burstMax Message Publishing Burst (Per Client)Number of messages that can be sent in a burst by a single client, on top of regular Messages Publish RatePause receiving client messages
max_conn_rateMax Connection Rate (Listener)The number of connections per second for the current listenerPause receiving new connections
max_conn_rateMax Connection Burst (Listener)The maximum number of connections that the listener can accept in burstsPause receiving new connections

Configure Listener-Level Limiters ​

You can set rate limits for each listener on the Management -> Listeners page in the Dashboard.

Alternatively, you can configure them through the configuration file. For example, to set limiters for the default TCP listener, configure it in the emqx.conf file as follows:

bash
listeners.tcp.default {
  bind = "0.0.0.0:1883"
  max_conn_rate = "1000/s"
  max_conn_burst = "10000/60m"
  messages_rate = "1000/s"
  messages_burst = "10000/60m"
  bytes_rate = "1MB/s"
  bytes_burst = "100MB/60m"
}

This configuration implies:

  • The maximum rate of connection establishment on the listener is 1000 per second.
  • The listener can accept a maximum of 10,000 connections within 60 minutes.
  • The maximum publishing rate for messages is 1000 per second per client.
  • The listener allows a burst of up to 10,000 messages within a short period every 60 minutes.
  • The maximum publishing rate for data is 1MB per second per client.
  • The listener allows a burst of up to 100MB within a short period every 60 minutes.

Node-Level Limiters ​

Limiters can also operate at the node level, limiting the speed of individual client connections to each EMQX node and the rate at which messages or data are published to the node. EMQX nodes use the following types of limiters to specify rate limits:

TypeDashboard UIDescriptionPost-Overload Behavior
bytes_rateData Publish RateThe amount of data (in bytes) sent by a single client to each EMQX nodeWhen the limit is reached, EMQX will drop QoS 0 messages and reject QoS 1 and QoS 2 messages with a "Quota Exceeded" error (0x97).
bytes_burstData Publish BurstThe burst amount of data allowed per client, based on the regular data publish rateWhen the limit is reached, EMQX will drop QoS 0 messages and reject QoS 1 and QoS 2 messages with a "Quota Exceeded" error (0x97).
messages_rateMessage Publish RateThe rate at which a single client sends messages to each EMQX nodeWhen the limit is reached, EMQX will drop QoS 0 messages and reject QoS 1 and QoS 2 messages with a "Quota Exceeded" error (0x97).
messages_burstMessage Publish BurstThe number of messages allowed to be sent per node in bursts, based on the regular message publishing rateWhen the limit is reached, EMQX will drop QoS 0 messages and reject QoS 1 and QoS 2 messages with a "Quota Exceeded" error (0x97).
max_conn_rateMaximum Connection RateThe rate at which new connections are accepted per nodeWhen the limit is reached, EMQX will pause processing connections in the Accept queue, delaying or rejecting new connections.
max_conn_burstMaximum Connection BurstThe maximum number of connections that a node can accept in burstsPause receiving new connections

Configuring Node-Level Limiters ​

You can configure rate limits for each node on the Management -> MQTT Configuration page in the Dashboard.

Alternatively, you can configure them through the configuration file. For example, you can configure the following in emqx.conf:

bash
mqtt.limiter {
  max_conn_rate = "1000/s"
  max_conn_burst = "10000/60m"
  messages_rate = "500/10s"
  messages_burst = "10000/60m"
  bytes_rate = "500KB/s"
  bytes_burst = "100MB/60m"
}

Zone-level limiters can be embedded in the zone section as follows:

bash
zones.my_zone.mqtt {
  limiter {...}
}
  • The node can receive a maximum of 500 messages every 10 seconds, and any excess will be dropped/rejected.
  • The node allows a burst of up to 10,000 messages within a short period every 60 minutes.
  • The node can receive a maximum of 500MB of data every 10 seconds, and any excess will be dropped/rejected.
  • The node allows a burst of up to 100MB within a short period every 60 minutes.

Rate Unit ​

Time Unit ​

The supported time unit in the rate value could be:

  • s : Second
  • m : Minute
  • h : Hour
  • d : Day

The time unit also can be an interval value, like 1000/10s means setting the limit to 1000 per every 10 seconds.

Size Unit ​

The supported size unit in the rate value could be:

  • KB : Kilobyte
  • MB : Megabyte
  • GB : Gigabyte
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