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This application can help clients automatically subscribe to topics compiled from user definitions when they connect, and the clients no longer need to send the MQTT SUBSCRIBE request.

How To Use

Add the following configuration items to the emqx.conf file

auto_subscribe {
    topics = [
        {
            topic = "c/${clientid}"
        },
        {
            topic = "client/${clientid}/username/${username}/host/${host}/port/${port}"
            qos   = 1
            rh    = 0
            rap   = 0
            nl    = 0
        }
    ]
}

This example defines two templates, all of which will be compiled into the final topic by replacing placeholders like ${clientid} ${port} with the actual values when the client connects.

Configuration

Configuration Definition

Field	Definition	Value Range	Default
auto_subscribe	Auto subscribe configuration	topics	topics
topics	Subscription Options	Subscription configurations list. See `Subscription Option`	[]

Subscription Option

Field	Definition	Value Range	Default
topic	Required. Topic template.	String, placeholders supported	No default value
qos	Optional. Subscription QoS	0 or 1 or 2. Refer to the MQTT QoS definition	0
rh	Optional. MQTT version 5.0. Whether to send retain message when a subscription is created.	0: Not send the retain message 1: Send the retain message	0
rap	Optional. MQTT version 5.0. When forwarding messages, Whether to send with retain flag	0: Set retain 0 1: Keep retain flag	0
nl	Optional. MQTT version 5.0. Whether the message can be forwarded to the client when published by itself	0: Forwarded to self 1: Not forwarded to self	0

Subscription Placeholders

Placeholder	Definition
${clientid}	Client ID
${username}	Client Username
${ip}	Client TCP connection local IP address
${port}	Client TCP connection local Port

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