Observability

YedMQ exposes lightweight broker observability through MQTT $SYS topics, the REST management API, and a node-local metrics endpoint.

$SYS topics

$SYS publishing reports the status of the current broker node. Numeric payloads are encoded as ASCII decimal strings, so MQTT clients can read values directly without decoding a binary counter byte.

Current $SYS values are node-local. In a cluster, subscribe to each node or use management tooling to query nodes individually when you need a full-cluster view.

Node-local metrics endpoint

The REST API exposes a protected metrics endpoint:

GET /metrics

The endpoint returns OpenMetrics-style text for the current node. It is intended for scraping each broker node independently.

The metrics endpoint does not aggregate cluster-wide state. For cluster topology and raft status, use the existing cluster management endpoints under /api/v1/cluster.

Operational model

• $SYS is useful for MQTT-native node status checks.
• /metrics is useful for Prometheus-compatible node scraping.
• Cluster operators should scrape every node and aggregate in the monitoring system.
• YedMQ does not currently expose a single built-in global cluster metrics endpoint.