EMQ X Delayed Publish

MQTT Delayed Publish Plugin.

Specification

A MQTT client can publish a delayed message to broker. A Delayed Publish Message is identified using a special style of Topic Name. The format is:

$delayed/{DelayInterval}/{TopicName}

• $delayed is a literal string that marks the Topic Name as being a delayed topic.
• {DelayInterval} The Delayed Interval which specifies the delay seconds of a MQTT message. The max interval allowed is 4294967.
• {TopicName} The topic name of a MQTT message

Exampels:

• $delayed/15/x/y: Publish the MQTT message to topic x/y 15 seconds later.
• $delayed/60//a/b: Publish the MQTT message to /a/b 1 minute later.
• $delayed/3600/$SYS/topic: Publish the MQTT message to $SYS/topic 1 hour later.

The MQTT broker should store a delayed message in memory or disc and then publish it when the delay expired.

Build

make && make tests

Load the Plugin

./bin/emqx_ctl plugins load emqx_delayed_publish

Example

mosquitto_pub -t "$delayed/10/delay1" -q 1 -m 'hello'
mosquitto_pub -t "$delayed/60/topic" -q 1 -m 'hello'

Implementation

• Store delayed messages in local ordered_set table
• Start a publish timer at interval of ttl of the first record
• Submit the publish task to emqx_pooler when timer expired

License

Apache License Version 2.0

Author

EMQ X Team.