Services

A service is a container the generated stack can run alongside the Ignition gateways: a database, an MQTT broker, an identity provider, a simulator, or an automation engine. Each one is a self-contained entry in the catalog under templates/services/<name>/, carrying its own manifest, compose fragment, and seed assets. Adding or changing a service is a data change, not a code change; see Adding a service.

The catalog

Service	Kind	Image	Provides
Postgres	database	postgres:18.1	sql-database, postgres-compatible
MySQL	database	mysql:9	sql-database, mysql-compatible
MariaDB	database	mariadb:11	sql-database, mysql-compatible
MongoDB	database	mongo:7	document-store
Keycloak	idp	quay.io/keycloak/keycloak:26.6.2	oidc-idp
Chariot	mqtt-broker	cirruslink/chariot:3.0.0	mqtt-broker
HiveMQ	mqtt-broker	hivemq/hivemq-ce:2025.5	mqtt-broker
EMQX	mqtt-broker	emqx/emqx:6.2.0	mqtt-broker
RabbitMQ	mqtt-broker	rabbitmq:4.3.1-management	mqtt-broker
Kafka	streaming	confluentinc/cp-kafka:8.2.1	kafka-broker
OPC-UA simulator	simulator	mcr.microsoft.com/iotedge/opc-plc:2.9.9	opcua-server
Modbus simulator	simulator	oitc/modbus-server:2.2.0	modbus-server
n8n	automation	n8nio/n8n:2.23.0	automation

Every image is pinned and overridable through an .env key (for example POSTGRES_IMAGE); each service page lists its own.

How services reach a stack

• Databases are chosen at the wizard's database prompt: Postgres (the default), MySQL, MariaDB, MongoDB, or none. The non-interactive --arch path uses Postgres.
• n8n is added as a service, optionally paired with the Ignition MCP module drop-in (mcp_dropin).
• Dependencies are pulled in by the resolver. A service that requires a capability gets it satisfied automatically: Keycloak requires sql-database, so it brings in Postgres (and a dedicated keycloak logical database) when none is present.

The brokers, the Kafka broker, the simulators, and Keycloak are full catalog entries: each ships a manifest, a compose fragment, seed assets, and a golden snapshot under tests/golden/services/. They are composed into a stack through the project's resolved services list, which the generation engine and resolver act on.

Capabilities and dependencies

Services describe themselves with two capability lists in their manifest:

• provides: the capabilities a service offers (Postgres provides sql-database).
• requires: the capabilities it needs from the rest of the stack (Keycloak requires sql-database).

The resolver matches requires against provides and adds whatever is missing, so a dependency never has to be selected by hand. It also applies one imperative coupling: selecting MySQL attaches the mysql-jdbc driver to every gateway, because Ignition ships no MySQL driver built in.

Seeding and post-setup

Most services run the moment their container is up, but the gateway-side connection often cannot be fully baked into the seed. Postgres is the exception: it file-seeds a working gateway db-connection and its secret. The other services declare the connections they defer to POST-SETUP.md, and each service page lists them. The seeding matrix is the underlying contract for what is file-seedable on Ignition 8.3 and what is not.