Integrations MQTT and Sparkplug B

MQTT and Sparkplug B

Verified live

Plain MQTT, or Sparkplug B as a full primary host application.

Verified against Eclipse Mosquitto 2.0, with crafted Tahu frames

As a primary host, the driver does the things the specification asks for and most integrations skip.

It publishes a retained STATE birth with a matching will, so edge nodes can see the host drop rather than inferring it from a timeout. The Sparkplug 3.0 form (spBv1.0/STATE/<host> carrying JSON) is the default, and legacyState selects the pre-3.0 ONLINE and OFFLINE string.

It tracks the per-node rolling sequence number and asks a node to rebirth when it skips, because a gap means messages were missed and the alias table can no longer be trusted.

It requests a rebirth after its own reconnect, because a host that was away has no idea what changed while it was gone.

It matches NDEATH to NBIRTH by bdSeq, so a death certificate left over from a previous session cannot kill the current one.

Addressing

Address	Means
`mqtt:plant/line1/temperature`	A scalar payload.
`mqtt:plant/line1/state\|data.temperature`	JSON, extracted by path.
`mqtt:plant/+/flow`	Wildcards work.
`spb:GroupId\|EdgeNodeId\|DeviceId\|Metric/Name`	A Sparkplug metric.
`spb:Plant\|Edge1\|\|Node/Uptime`	An empty device is a node-level metric.

The trap

Delivering Sparkplug messages concurrently reorders them, which makes a healthy node look like it is dropping messages and provokes a rebirth storm. Message ordering is enforced.

Configuration

legacyState