tracing

Enables integration with OpenTelemetry tracing facilities, using opentelemetry-go .

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

It uses gRPC as an exporter protocol and W3C tracecontext and baggage as propagators.

The trace ID and span ID are added to access logs 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 to pass the IDs to your app.

Syntax

tracing {
	span <span_name>
	span_attributes {
		<attr1> <value1>
		<attr2> <value2>
	}
}

• <span_name> is a span name. Please see span naming guidelines.

• <span_attributes> are additional attributes attached to each recorded span. Many span attributes are set by default according to OTEL Semantic conventions for HTTP spans like details about the request, response and client.

  Placeholders may be used in span names and attributes. Keep in mind that the span name is set before the request is forwarded, so only request placeholders may be used. All placeholders are available in span attributes.

Configuration

Environment variables

It can be configured using the environment variables defined by the OpenTelemetry Environment Variable Specification.

For the exporter configuration details, please see spec.

For example:

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:

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

	handle {
		tracing {
			span app
			span_attributes {
				user_id {http.request.cookie.user-id}
			}
		}
		reverse_proxy localhost:8080
	}
}