spin-trigger-mqtt VS mosquitto

The MQTT trigger is a feature of the Spin framework that allows a Spin application to subscribe to a specific MQTT address. Individual components within that application can then be configured to monitor particular topics at the address. When messages are detected on these topics, the corresponding component functions are triggered.

Let’s start by looking at the implementation of our first component, which is triggered by messages published to an MQTT topic and persists the data in a SQLite database. It is implemented in Rust and was scaffolded using the MQTT template. In the Spin application manifest (spin.toml), we are using a Spin application variable to dynamically configure the address for the MQTT broker. This will enable us to set Spin to connect to a broker at "mqtt://localhost:1883" when running locally and at "mqtt://emqx.default.svc.cluster.local:1883" when running in SpinKube. We also set the keep alive interval (secs) for connections with the broker and username and password authentication credentials. In this example application, the broker does not require authentication, so the credentials are left empty.

I am on Ubuntu, so installing and running an MQTT broker is fairly simple. We will use an open source MQTT broker called Mosquitto from hereon out. If you are connecting to a different remote MQTT broker, you might want to skip this step: