Instrument outgoing Dio requests with client spans, trace-context propagation, and selected HTTP headers.

Dio

comon_otel_dio adds OtelDioInterceptor on top of comon_otel.

Minimal setup

import 'package:comon_otel/comon_otel.dart';
import 'package:comon_otel_dio/comon_otel_dio.dart';
import 'package:dio/dio.dart';

Future<void> main() async {
  await Otel.init(
    serviceName: 'shopping-api-client',
    exporter: OtelExporter.console,
  );

  final dio = Dio()
    ..interceptors.add(OtelDioInterceptor());

  await dio.get('https://example.com/users');
  await Otel.shutdown();
}

What it does

creates one client span per request
injects the current trace context into outgoing headers
records common HTTP semantic attributes
maps 5xx and transport failures to error span status
optionally captures selected request and response headers

Common tuning

final dio = Dio()
  ..interceptors.add(
    OtelDioInterceptor(
      requestFilter: (options) => !options.path.startsWith('/health'),
      spanNameBuilder: (options) => 'api ${options.method} ${options.uri.path}',
      captureRequestHeaders: const <String>{'x-request-id'},
      captureResponseHeaders: const <String>{'content-type', 'x-request-id'},
    ),
  );

Redaction

Sensitive headers are redacted by default when captured. That keeps the feature safer than blindly copying all outbound or inbound headers.

W3C propagation

The interceptor relies on the SDK propagator installed during Otel.init(). In the default setup, that means W3C trace-context and baggage are injected automatically.

Practical rule

Capture only the headers you truly need. Full header capture is usually noisy and often risky for privacy or secret handling.

Dio