[mqtt] Reuse connections #448

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opened 2025-05-09 23:30:53 +02:00 by blacklight · 0 comments

blacklight commented

2025-05-09 23:30:53 +02:00

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As of now integrations like zigbee.mqtt and zwave.mqtt that extend the MqttPlugin and do a lot of publish+subscribe cycles are subject to big reconnection overheads - the current implementation of mqtt.publish closes the client after the response has been received.

If I have to query the state of many devices on a Zigbee or Z-Wave network, this can mean dozens of reconnections in a short time span.

A better implementation should:

Retain an MQTT connection open on the MqttPlugin level, on a <host>:<port> basis.
Add new subscriptions to the existing connection when needed.
Internally dispatch calls to on_message to the right subscription(s) on a topic basis.
Close the connection only when the plugin is stopped or when the last topic is unsubscribed - and only after a given keepalive time.

As of now integrations like `zigbee.mqtt` and `zwave.mqtt` that extend the `MqttPlugin` and do a lot of publish+subscribe cycles are subject to big reconnection overheads - the current implementation of `mqtt.publish` closes the client after the response has been received. If I have to query the state of many devices on a Zigbee or Z-Wave network, this can mean dozens of reconnections in a short time span. A better implementation should: 1. Retain an MQTT connection open on the `MqttPlugin` level, on a `<host>:<port>` basis. 2. Add new subscriptions to the existing connection when needed. 3. Internally dispatch calls to `on_message` to the right subscription(s) on a topic basis. 4. Close the connection only when the plugin is stopped or when the last topic is unsubscribed - and only after a given `keepalive` time.