ADR-0212: The broker client is wired by OpenBroker's starter

• Status: accepted
• Date: 2026-10-27
• Deciders: Mahdi Amirabdollahi
• Change: openspec/changes/19e2b-rahdar-on-the-openbroker-starter
• Builds on: ADR-0203, ADR-0211

Context

Rahdar opens one OpenBroker connection per registered cluster, at runtime, and built every part of its options by hand: the drivers, SSL-bundle TLS with reload, the interceptor, the clock, and an OpenTelemetry observer wrapped so that it never writes into a message. OpenBroker 0.4.0 ships a Spring Boot starter that provides these building blocks for applications that open connections at runtime, records messaging metrics through Micrometer, and can trace sends without writing into the message. Its other parts (connections from configuration or from Spring's Kafka and Artemis settings, health per connection, a processor lifecycle) are made for applications whose brokers are their own dependencies, not for a product that manages other people's brokers.

Decision

Rahdar takes from the starter the drivers, each cluster's connect options, SSL-bundle TLS, the link listener and the observers, with openbroker.tracing.inject-context: false, and removes its own versions. Messaging metrics become Micrometer meters tagged with the cluster, and spans stay in OpenTelemetry. Rahdar keeps, through one ConnectOptionsCustomizer:

• the live broker timeouts, which Settings changes without reconnecting (ADR-0010);
• identity context propagation, so a broker callback never runs with the context of the thread that started it, such as an operator's request that started a plugin consumer.

Rahdar turns off connections derived from Spring's settings and declares none in configuration; cluster health and the plugin consumers' shutdown order stay Rahdar's.

Consequences

• Less wiring code in platform/broker, and the SDK's own defaults and fixes arrive with each OpenBroker release.
• Messaging metrics reach Prometheus and OTLP with the rest of Rahdar's metrics (ADR-0147), under the names the OpenTelemetry observer used before.
• Rahdar depends on the starter's API for runtime connections; a change there is an OpenBroker release note to follow.
• A Spring spring.kafka.* or spring.artemis.* property never creates a hidden broker connection.

Alternatives considered

• Keep the hand-built wiring: a second copy of what the SDK now ships, maintained apart.
• Adopt the whole starter, with clusters in configuration: clusters are registered in the product, and a managed broker must not decide Rahdar's readiness.
• The starter's Micrometer context propagation: it would carry an operator's identity into long-lived consumer threads.