Metrics Part 1 - Add Counter Metric API

CHANGELOG.md

@@ -2,6 +2,21 @@
 
 ## Unreleased
 
+### Features
+
+- Experimental: Add support for Sentry Developer Metrics ([#1940](https://github.com/getsentry/sentry-dart/pull/1940), [#1949](https://github.com/getsentry/sentry-dart/pull/1949), [#1954](https://github.com/getsentry/sentry-dart/pull/1954), [#1958](https://github.com/getsentry/sentry-dart/pull/1958))  
+  Use the Metrics API to track processing time, download sizes, user signups, and conversion rates and correlate them back to tracing data in order to get deeper insights and solve issues faster. Our API supports counters, distributions, sets, gauges and timers, and it's easy to get started:
+  ```dart
+  Sentry.metrics()
+      .increment(
+      'button_login_click', // key
+      value: 1.0,
+      unit: null,
+      tags: {"provider": "e-mail"}
+  );
+  ```
+  To learn more about Sentry Developer Metrics, head over to our [Dart](https://docs.sentry.io/platforms/dart/metrics/) and [Flutter](https://docs.sentry.io/platforms/flutter/metrics/) docs page.
+
 ### Dependencies
 
 - Expand `package_info_plus` version range to `6.0.0` ([#1948](https://github.com/getsentry/sentry-dart/pull/1948))

dart/lib/src/hub.dart

@@ -2,6 +2,9 @@ import 'dart:async';
 import 'dart:collection';
 
 import 'package:meta/meta.dart';
+import 'metrics/metric.dart';
+import 'metrics/metrics_aggregator.dart';
+import 'metrics/metrics_api.dart';
 import 'profiling.dart';
 import 'propagation_context.dart';
 import 'transport/data_category.dart';
@@ -38,6 +41,14 @@ class Hub {
 
   late final _WeakMap _throwableToSpan;
 
+  late final MetricsApi _metricsApi;
+
+  @internal
+  MetricsApi get metricsApi => _metricsApi;
+
+  @internal
+  MetricsAggregator? get metricsAggregator => _peek().client.metricsAggregator;
+
   factory Hub(SentryOptions options) {
     _validateOptions(options);
 
@@ -49,6 +60,7 @@ class Hub {
     _stack.add(_StackItem(_getClient(_options), Scope(_options)));
     _isEnabled = true;
     _throwableToSpan = _WeakMap(_options);
+    _metricsApi = MetricsApi(hub: this);
   }
 
   static void _validateOptions(SentryOptions options) {
@@ -554,6 +566,42 @@ class Hub {
     return sentryId;
   }
 
+  @internal
+  Future<SentryId> captureMetrics(
+      Map<int, Iterable<Metric>> metricsBuckets) async {
+    var sentryId = SentryId.empty();
+
+    if (!_isEnabled) {
+      _options.logger(
+        SentryLevel.warning,
+        "Instance is disabled and this 'captureMetrics' call is a no-op.",
+      );
+    } else if (!_options.enableMetrics) {
+      _options.logger(
+        SentryLevel.info,
+        "Metrics are disabled and this 'captureMetrics' call is a no-op.",
+      );
+    } else if (metricsBuckets.isEmpty) {
+      _options.logger(
+        SentryLevel.info,
+        "Metrics are empty and this 'captureMetrics' call is a no-op.",
+      );
+    } else {
+      final item = _peek();
+      try {
+        sentryId = await item.client.captureMetrics(metricsBuckets);
+      } catch (exception, stackTrace) {
+        _options.logger(
+          SentryLevel.error,
+          'Error while capturing metrics.',
+          exception: exception,
+          stackTrace: stackTrace,
+        );
+      }
+    }
+    return sentryId;
+  }
+
   @internal
   void setSpanContext(
     dynamic throwable,

dart/lib/src/hub_adapter.dart

@@ -4,6 +4,9 @@ import 'package:meta/meta.dart';
 import 'hint.dart';
 
 import 'hub.dart';
+import 'metrics/metric.dart';
+import 'metrics/metrics_aggregator.dart';
+import 'metrics/metrics_api.dart';
 import 'profiling.dart';
 import 'protocol.dart';
 import 'scope.dart';
@@ -23,6 +26,10 @@ class HubAdapter implements Hub {
   @internal
   SentryOptions get options => Sentry.currentHub.options;
 
+  @override
+  @internal
+  MetricsApi get metricsApi => Sentry.currentHub.metricsApi;
+
   factory HubAdapter() {
     return _instance;
   }
@@ -181,4 +188,12 @@ class HubAdapter implements Hub {
 
   @override
   Scope get scope => Sentry.currentHub.scope;
+
+  @override
+  Future<SentryId> captureMetrics(Map<int, Iterable<Metric>> metricsBuckets) =>
+      Sentry.currentHub.captureMetrics(metricsBuckets);
+
+  @override
+  MetricsAggregator? get metricsAggregator =>
+      Sentry.currentHub.metricsAggregator;
 }

dart/lib/src/metrics/local_metrics_aggregator.dart

@@ -0,0 +1,37 @@
+import 'dart:core';
+import 'package:meta/meta.dart';
+import '../protocol/metric_summary.dart';
+import 'metric.dart';
+
+@internal
+class LocalMetricsAggregator {
+  // format: <export key, <metric key, gauge>>
+  final Map<String, Map<String, GaugeMetric>> _buckets = {};
+
+  void add(final Metric metric, final num value) {
+    final bucket =
+        _buckets.putIfAbsent(metric.getSpanAggregationKey(), () => {});
+
+    bucket.update(metric.getCompositeKey(), (m) => m..add(value),
+        ifAbsent: () => Metric.fromType(
+            type: MetricType.gauge,
+            key: metric.key,
+            value: value,
+            unit: metric.unit,
+            tags: metric.tags) as GaugeMetric);
+  }
+
+  Map<String, List<MetricSummary>> getSummaries() {
+    final Map<String, List<MetricSummary>> summaries = {};
+    for (final entry in _buckets.entries) {
+      final String exportKey = entry.key;
+
+      final metricSummaries = entry.value.values
+          .map((gauge) => MetricSummary.fromGauge(gauge))
+          .toList();
+
+      summaries[exportKey] = metricSummaries;
+    }
+    return summaries;
+  }
+}