# Observability


The transport emits OpenTelemetry activities under the source `NServiceBus.Transport.NonDurable`.

| Activity name | Kind | Description |
|:---|:---|:---|
| `NServiceBus.Transport.NonDurable.Send` | Producer | A message is dispatched to a destination queue. |
| `NServiceBus.Transport.NonDurable.Schedule` | Producer | A delayed delivery message is scheduled. |
| `NServiceBus.Transport.NonDurable.Process` | Consumer | A message is received and processed. |

These activities describe the raw transport interactions and are emitted under the transport's own activity source. Enabling or configuring the [NServiceBus Core OpenTelemetry](/nservicebus/operations/opentelemetry.md) does not change this behavior. Core emits its own activities under the `NServiceBus.Core` source. Options such as `StartNewTraceOnReceive()` and `ContinueExistingTraceOnReceive()` control how Core's activities correlate to each other; they do not affect the transport activities described here.

## Span correlation

The `Process` span is a root span. It correlates to the producer span that created the message through an [activity link](https://opentelemetry.io/docs/concepts/signals/traces/), following the [OpenTelemetry messaging semantic conventions](https://opentelemetry.io/docs/specs/semconv/messaging/). The producer span is parented to the handler activity that performed the send.

Keeping the consumer side of each hop a root span prevents trace depth from growing with every hop in self-feeding and saga message chains. Each message's processing is a bounded sub-trace, with causal linkage preserved via the link.

```mermaid
flowchart LR;
  subgraph PRODUCER
  direction TB
   SEND[NServiceBus.Transport.NonDurable.Send span]
  end
  subgraph CONSUMER
  direction TB
   PROCESS[NServiceBus.Transport.NonDurable.Process span]
  end
  SEND-. link .-PROCESS;
```

With [inline execution](/transports/non-durable/index.md#inline-execution) enabled, a message processed synchronously within the send uses the producer span as its parent. The `Process` span is a child of the `Send` span and carries no links, mirroring the synchronous call stack.

```mermaid
flowchart LR;
  subgraph PRODUCER
  direction TB
   SEND[NServiceBus.Transport.NonDurable.Send span]
  end
  subgraph CONSUMER
  direction TB
   PROCESS[NServiceBus.Transport.NonDurable.Process span]
  end
  SEND--child--> PROCESS;
```

Delayed delivery is processed asynchronously by the message pump even when inline execution is enabled. Delayed messages therefore keep the root span and link correlation described above.

Tags include `messaging.system = nondurable`, `messaging.destination.name`, `messaging.operation.name`, `messaging.message.id`, and `messaging.message.conversation_id`.