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.