The Thin Edge MQTT bus
Sending measurements to thin-edge.io
The thin-edge.io framework exposes some MQTT endpoints that can be used by local processes
to exchange data between themselves as well as to get some data forwarded to the cloud.
It will essentially act like an MQTT broker against which you can write your application logic.
Other thin-edge processes can use this broker as an inter-process communication mechanism by publishing and
subscribing to various MQTT topics.
Any data can be forwarded to the connected cloud-provider as well, by publishing the data to some standard topics.
All topics with the prefix tedge/ are reserved by thin-edge.io for this purpose.
To send measurements to thin-edge.io, the measurements represented in Thin Edge JSON format can be published
to the tedge/measurements topic.
Other processes running on the thin-edge device can subscribe to this topic to process these measurements.
If the messages published to this tedge/measurements topic is not a well-formed Thin Edge JSON,
then that message won’t be processed by thin-edge.io, not even partially,
and an appropriate error message on why the validation failed will be published to a dedicated tedge/errors topic.
The messages published to this topic will be highly verbose error messages and can be used for any debugging during development.
You should not rely on the structure of these error messages to automate any actions as they are purely textual data
and bound to change from time-to-time.
More topics will be added under the tedge/ topic in future to support more data types like events, alarms etc.
So, it is advised to avoid any sub-topics under tedge/ for any other data exchange between processes.
Here is the complete list of topics reserved by thin-edge.io for its internal working:
| Topic | Description |
|---|---|
tedge/ | Reserved root topic of thin-edge.io |
tedge/measurements | Topic to publish measurements to thin-edge.io |
tedge/errors | Topic to subscribe to receive any error messages emitted by thin-edge.io while processing measurements |
Sending measurements to the cloud
The thin-edge.io framework allows users forward all the measurements generated and published to
tedge/measurements MQTT topic in the thin-edge device to any IoT cloud provider that it is connected to,
with the help of a mapper component designed for that cloud.
The responsibility of a mapper is to subscribe to the tedge/measurements topic to receive all incoming measurements
represented in the cloud vendor neutral Thin Edge JSON format, to a format that the connected cloud understands.
Refer to Cloud Message Mapper Architecture for more details on the mapper component.