Auto Subscribe

With Auto Subscription enabled, users can set multiple EMQX rules. After a client is successfully connected to EMQX, EMQX will complete the subscription process for the client automatically, and the clients no longer need to send SUBSCRIBE requests.

Before EMQX 5.0, this feature is called Proxy Subscription.

# Configuration

# Configuration Definition

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

# Subscription Option

Field	Definition	Range	Default
topic	Required. Topic	String, placeholders supported	No default value
qos	Not Required. Subscription QoS	0 or 1 or 2. Refer to the MQTT QoS definition	0
rh	Not Required. 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	Not Required. MQTT version 5.0. When forwarding messages, Whether to send with retain flag	0: Set retain 0 1: Keep retain flag	0
nl	Not Required. 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

# Quick Start

Add the following configuration items to the configuration file

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

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+---------------------------+             +----------------+
| clientid: demo_client1    |             |  EMQX Broker   |
| username: admin | | |
| local host: 192.168.1.234 | <---------> |                |
| local port: 55678         |             |                |
+---------------------------+             +----------------+

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When the client uses versions lower than 5, the following subscriptions are available after connection.

topic: c/demo_client1
qos: 0

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topic: client/demo_client1/username/admin/host/192.168.1.234/port/55678
qos: 1

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When the client uses version 5, the following subscriptions are available after connection.

topic: c/demo_client1
qos: 0
rh: 0
rap: 0
nl: 0

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topic: client/demo_client1/username/admin/host/192.168.1.234/port/55678
qos: 1
rh: 0
rap: 0
nl: 0