Transport Metrics

ID: transport.metrics
Name: Transport metrics
Maturity: GA
Summary: Shared OpenTelemetry meter and observable circuit-breaker gauges for all transport adapters.

What It Does

TransportMetricsRegistration.RegisterIfNeeded installs one startup initializer (TransportObservableMetricsInitializer) and optional broker identity (TransportBrokerIdentity). The initializer creates TransportObservableMetrics, which exports aggregate publisher state from ITransportCircuitBreakerRegistry.

Applications subscribe with AddLiteBusTransportMetrics(). AMQP package keeps compatibility alias AddLiteBusAmqpMetrics() and points to the same shared meter.

Public Surface

API	Role
`TransportMetricsRegistration.RegisterIfNeeded(IModuleConfiguration, string? broker)`	One-time registration of metrics hooks
`TransportObservableMetricsInitializer`	Startup task that creates gauges
`TransportObservableMetrics`	Gauge producer bound to aggregate publisher breaker state
`TransportBrokerIdentity`	Broker tag identity value
`TransportMetricsRegisteredMarker`	Marker to prevent duplicate registration
`AddLiteBusTransportMetrics()`	OpenTelemetry meter registration extension
`AddLiteBusAmqpMetrics()`	AMQP alias to shared meter
`LiteBusTransportTelemetry` constants	Stable meter, instrument, and tag names

Packages

LiteBus.Transport
LiteBus.Transport.Extensions.OpenTelemetry
LiteBus.Transport.Amqp.Extensions.OpenTelemetry (alias)

Requires

transport.circuit-breaker
Host startup execution for IStartupTask

Invariants

Shared meter name is LiteBus.Transport.
Public gauge names remain stable on LiteBusTransportTelemetry.
Registration is idempotent per module configuration.

Non-Goals

Per-message publish and consume counters.
Prebuilt dashboard bundles.
Legacy AMQP-only meter names from pre-v6.

Observability

Shared Meter Contract

Constant	Value
`LiteBusTransportTelemetry.MeterName`	`LiteBus.Transport`
`LiteBusTransportTelemetry.BrokerTagName`	`litebus.transport.broker`
`LiteBusTransportTelemetry.CircuitBreakerOpenInstrumentName`	`litebus.transport.circuit_breaker.open`
`LiteBusTransportTelemetry.CircuitBreakerFailureCountInstrumentName`	`litebus.transport.circuit_breaker.failure_count`

Observable Gauges

Instrument	Source	Value
`litebus.transport.circuit_breaker.open`	`ITransportCircuitBreakerRegistry.IsAnyOpen`	`1` when any publisher circuit is open or half-open; otherwise `0`
`litebus.transport.circuit_breaker.failure_count`	`ITransportCircuitBreakerRegistry.FailureCount`	sum of current failures across publisher circuits

Broker Tag Values

Broker	Tag value
AMQP	`amqp`
Kafka	`kafka`
AWS SQS	`sqs`
Azure Service Bus	`azure_service_bus`
In-memory	`inmemory`

OpenTelemetry Registration

Extension	Package	Effect
`AddLiteBusTransportMetrics()`	`LiteBus.Transport.Extensions.OpenTelemetry`	Adds meter `LiteBus.Transport`
`AddLiteBusAmqpMetrics()`	`LiteBus.Transport.Amqp.Extensions.OpenTelemetry`	Adds the same meter

Test Coverage

Covered

Test method	Project
`RecordFailure_until_threshold_ShouldOpenCircuitAndExposeFailureCount`	`LiteBus.Transport.UnitTests` (`Amqp/`)
`RecordSuccess_after_failures_ShouldCloseCircuit`	`LiteBus.Transport.UnitTests` (`Amqp/`)
`ObservableGauges_ShouldReportBreakerStateAndStopAfterDisposal`	`LiteBus.Transport.UnitTests`
`ProcessPendingAsync_WhenCircuitBreakerOpen_ShouldNotPublish`	`LiteBus.Durable.IntegrationTests` (`Dispatch/Outbox/Kafka/`, `Dispatch/Outbox/AwsSqs/`)

Untested

Assertions for startup task registration and execution in host composition tests.
Assertions for OpenTelemetry meter provider subscription (AddLiteBusTransportMetrics, AddLiteBusAmqpMetrics).
Broker-tagged gauge export assertions.

Out-of-Scope

Transport-level throughput and latency histograms.
Bundled exporter configurations.