---
title: tracing (Caddyfile directive)
---

# tracing

Enables integration with OpenTelemetry tracing facilities, using [`opentelemetry-go` <img src="/old/resources/images/external-link.svg" class="external-link">](https://github.com/open-telemetry/opentelemetry-go).

When enabled, it will propagate an existing trace context or initialize a new one.

It uses [gRPC](https://github.com/grpc/) as an exporter protocol and  W3C [tracecontext](https://www.w3.org/TR/trace-context/) and [baggage](https://www.w3.org/TR/baggage/) as propagators.

The trace ID and span ID are added to [access logs](/docs/caddyfile/directives/log) as the standard `traceID` and `spanID` fields. Additionally, the `{http.vars.trace_id}` and `{http.vars.span_id}` placeholders are available; for example, you can use them in a [`request_header`](request_header) to pass the IDs to your app.



## Syntax

```caddy-d
tracing {
	[span <span_name>]
}
```

- **&lt;span_name&gt;** is a span name. Please see span [naming guidelines](https://github.com/open-telemetry/opentelemetry-specification/blob/v1.7.0/specification/trace/api.md).

  [Placeholders](/docs/caddyfile/concepts#placeholders) may be used in span names; keep in mind that tracing happens as early as possible, so only request placeholders may be used, and not response placeholders.



## Configuration

### Environment variables

It can be configured using the environment variables defined
by the [OpenTelemetry Environment Variable Specification](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/sdk-environment-variables.md).

For the exporter configuration details, please
see [spec](https://github.com/open-telemetry/opentelemetry-specification/blob/v1.7.0/specification/protocol/exporter.md).

For example:

```bash
export OTEL_EXPORTER_OTLP_HEADERS="myAuthHeader=myToken,anotherHeader=value"
export OTEL_EXPORTER_OTLP_TRACES_ENDPOINT=https://my-otlp-endpoint:55680
```



## Examples

Here is a **Caddyfile** example:

```caddy
example.com {
	handle /api* {
		tracing {
			span api
		}
		request_header X-Trace-Id {http.vars.trace_id}
		reverse_proxy localhost:8081
	}

	handle {
		tracing {
			span app
		}
		reverse_proxy localhost:8080
	}
}
```