otel_provider 0.1.0-beta.1

OpenTelemetry instrumentation for `package:provider`. A mixin on `ChangeNotifier` that emits short spans on every notifyListeners / dispose. Works with any ChangeNotifier — provider just happens to be [...]

otel_provider

OpenTelemetry instrumentation for package:provider and any code using ChangeNotifier. Built on the Dartastic OpenTelemetry SDK.

Mix in OTelChangeNotifierMixin on your notifier and every notifyListeners() + dispose() produces a short span — your state-mutation timeline in Tempo, automatically.

class CartModel extends ChangeNotifier with OTelChangeNotifierMixin {
  final _items = <Item>[];
  void add(Item i) {
    _items.add(i);
    notifyListeners(); // span emitted here
  }
}

The notifier machinery lives in Flutter foundation, not in package:provider itself, so this package works for any ChangeNotifier — pure-Flutter code, GetX models that happen to be ChangeNotifiers, custom solutions, all of them. The name is provider because that's the most common consumer.

Why mix in, not wrap?

A ChangeNotifierProvider wrapper widget can't see notifications — the only way to hook them is from inside the notifier itself. The mixin pattern is the cleanest version of that: minimal viral spread through your code (one extra with clause), no behavior changes, no API for downstream callers to learn.

Span shape

Hook	Span name	Status
notifyListeners (when hasListeners)	notifier.notify:<runtimeType>	unset
dispose	notifier.disposed:<runtimeType>	unset

Attribute	Source	When set
notifier.name	runtimeType.toString()	every span
notifier.event	notify / disposed	every span
notifier.value	value.toString() (clipped)	only on ValueNotifier-style classes with otelRecordValues == true
notifier.value.type	value.runtimeType	same conditions

notifyListeners with no current listeners short-circuits — no span is emitted. This matches ChangeNotifier's own behavior (it doesn't dispatch when nobody is listening), and prevents off-screen models from polluting your Tempo view with noise.

ValueNotifier support

When you mix the OTel mixin into a ValueNotifier<T>, you can opt into recording the value itself by overriding otelRecordValues:

class _Search extends ValueNotifier<String> with OTelChangeNotifierMixin {
  _Search(super.initial);

  @override
  bool get otelRecordValues => true;

  @override
  int get otelValueMaxLength => 64;
}

Off by default because notifier values often carry user data.

Caveats

• Resolves the tracer lazily on first emit, so it's safe to mix this in even before OTel.initialize() runs. The tracer is cached after first use.
• The notifier.notify span is emitted before super.notifyListeners() fires, so it appears before listeners are notified — the natural order for trace causality.
• package:provider's ChangeNotifierProvider auto-disposes its notifier when the surrounding widget tree unmounts. The dispose span will fire then.

License

Apache 2.0 — see LICENSE.