Wire an IIoT pipeline

The --iiot overlay adds a Sparkplug B MQTT pipeline to any topology: an MQTT broker plus the Cirrus Link Transmission and Engine modules, wired to the gateways by role:

• Edge-side gateways (spokes in hub-and-spoke, frontends in scale-out) get Transmission — they publish Sparkplug messages to the broker.
• Central gateways (hub, backend) get Engine — they subscribe and aggregate.
• Single-gateway stacks (basic) get both — a self-contained publish/subscribe loop for local development.

The connection seeds are written at generation time: each gateway boots with its Sparkplug identity already set and its broker connection configured, so the pipeline forms with no UI clicks.

Enable the overlay

Pass --iiot to create to add the overlay with the default broker (chariot):

ignition-stack create demo --arch hub-and-spoke --iiot

To choose a different broker, pass --iiot-broker <slug> (which implies --iiot):

ignition-stack create demo --arch hub-and-spoke --iiot-broker emqx

The broker slug must be a catalog mqtt-broker kind. The available options are:

Slug	Broker	Notes
chariot	Cirrus Link Chariot	Default. Requires a license — the generated stack ships a trial init container. Live-verified end-to-end on 8.3.6 + Chariot 3.0.0.
emqx	EMQX CE	Anonymous access; no credentials. Connection seeds are config-shaped (not separately live-verified).
hivemq	HiveMQ CE	Anonymous access; no credentials. Connection seeds are config-shaped.
rabbitmq	RabbitMQ	Credentials seeded via embedded JWE. Connection seeds are config-shaped.

In the wizard

The IIoT prompt appears after the redundancy step:

? Add IIoT (MQTT/Sparkplug)?  No

Accepting opens a broker select defaulting to chariot. The overlay is applied to the resolved config before generation.

What gets generated

For a hub-and-spoke stack with --iiot (three spokes, hub + broker on the same host):

• The broker service is added to the stack's service registry.
• Each spoke gets the MQTT Transmission module (.modl in user-lib/modules/, ACCEPT_MODULE_LICENSES and ACCEPT_MODULE_CERTS env vars set).
• The hub gets the MQTT Engine module.
• Both modules are pinned with fixed download URLs in modules.yaml.
• Sparkplug identity seeds are written for every Transmission gateway:
  • Group ID = the project name
  • Edge Node ID = the gateway name
  • Broker connection = tcp://<broker-host>:<port> with credentials embedded as a JWE blob
• The hub's Engine seeds point the same broker and subscribe to spBv1.0/# by default.

The Cirrus Link module identifier (e.g. com.cirruslink.mqtt.transmission.gateway) is read from the broker manifest rather than hardcoded, so different broker flavors can wire different module pairs.

Chariot trial gate

Chariot's MQTT listener will not open without an active license. The generated stack ships a one-shot init container that fires the trial-start REST call at container-up time:

POST {chariot_base_url}/license?action=start-trial-timer

This gives a fresh deployment a working pipeline automatically. For a real deployment, replace the init container with a valid LICENSE_TYPE environment variable.

Ignition trial interaction: Ignition itself has a ~2-hour platform trial. The Cirrus modules run inside that trial window, so the pipeline will stop working when the trial expires. The reliable reset is the Reset Trial button in the Ignition gateway UI (or POST /data/api/v1/trial). A volume wipe is always a clean slate. Demo posture only.

In the composer

The composer (reached from the summary's Tweak action) exposes an explicit action:

? Composer action?  Add or remove IIoT (MQTT/Sparkplug)

This applies or removes the same overlay: one broker instance, Transmission attachments on edge-side roles, Engine on central roles. The broker select appears when wiring.

You can also wire a broker by hand and choose its role:

• Add a service → select the broker → attach to gateway(s) → choose mqtt-transmission or mqtt-engine.
• Share an existing instance → select the broker → choose the attachment role.

Every mutation is validated immediately; wiring an Edge gateway as Engine, or wiring two brokers, is rejected up front.

In a declarative config

The overlay's result in a saved config is a ServiceInstance for the broker plus mqtt-transmission and mqtt-engine attachment roles on the gateways:

name: plant
gateways:
  - name: hub
    role: hub
    services:
      - instance: chariot
        role: mqtt-engine
  - name: spoke-1
    role: spoke
    ignition_edition: edge
    services:
      - instance: chariot
        role: mqtt-transmission
service_instances:
  - id: chariot
    service: chariot

The attachment role drives which Cirrus module the resolver installs on that gateway. consumer (the default) attaches to the broker container's network without installing either module — useful for external subscribers.

Use create --dry-run --iiot to dump the resolved config and inspect the full shape before building.