Tracing

The Mercure.rocks Hub emits OpenTelemetry spans for its main internal operations:

Span name	Kind	Description
`mercure.publish`	Producer	Covers the publish flow: authorization, validation, and dispatch to the transport
`mercure.subscribe`	Consumer	Covers subscription setup: authorization, history replay, and transport registration
`mercure.subscriptions`	Internal	Covers requests to the subscription API (`/.well-known/mercure/subscriptions/...`)
`mercure.transport.history`	Internal	Covers history replay from the storage transport (Bolt, Redis...)

Mercure's spans nest under the HTTP request span produced by Caddy's tracing directive, so enable it to start collecting traces:

route {
	tracing
	mercure {
		# ...
	}
}

Exporters, endpoints (OTLP gRPC or HTTP), protocols, resource attributes, and propagators are all configured through the standard OTEL_* environment variables. When the tracing directive is not enabled, Mercure's spans are no-ops and have no runtime cost.