Initial backend for metrics in Observatory

runtime/lib/profiler.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import "dart:_internal";
+import 'dart:convert';
 
 patch class UserTag {
   /* patch */ factory UserTag(String label) {
     return new _UserTag(label);
   }
   /* patch */ static UserTag get defaultTag => _getDefaultTag();
 }
 
 
 class _UserTag implements UserTag {
   factory _UserTag(String label) native "UserTag_new";
   String get label native "UserTag_label";
   UserTag makeCurrent() native "UserTag_makeCurrent";
 }
 
 patch UserTag getCurrentTag() => _getCurrentTag();
 UserTag _getCurrentTag() native "Profiler_getCurrentTag";
 
 UserTag _getDefaultTag() native "UserTag_defaultTag";
+
+/// A measurement.
+abstract class Metric {
+  final String _id;
+  final String name;
+  final String description;
+  double _value = 0.0;
+
+  double get value => _value;
+
+  Metric(this.name, this.description)
+      : _id = '${Metrics._idCounter++}';
+
+  Map _toJSON();
+}
+
+/// A measured value, with an optional min and max.
+class Gauge extends Metric {
+  final double min;
+  final double max;
+
+  Gauge(String name, String description)
+      : min = null,
+        max = null,

[srdjan, 2014/07/29 00:30:01]

Why setting it to null a second time (first at allocation, implicitly)?

+        super(name, description);
+
+  Gauge.range(String name, String description, this.min, this.max)
+      : super(name, description) {
+    if ((min == null) || (max == null)) {
+      throw new ArgumentError('min and max cannot be null.');

[srdjan, 2014/07/29 00:30:01]

the min/max is! double should also cover min/max == null test.

+    }
+    if ((min is! double) || (max is! double)) {
+      throw new ArgumentError('min and max must be doubles.');
+    }
+    if (min >= max) {
+      throw new ArgumentError('min must be less than max.');
+    }
+  }
+
+  set value(double v) {
+    _value = v;
+  }
+
+  Map _toJSON() {
+    var map = {
+      'type': 'Gauge',
+      'id': 'metrics/$_id',
+      'name': name,
+      'description': description,
+      'value': _value,
+    };
+    if (min != null) {
+      map['min'] = min;
+      map['max'] = max;
+    }
+    return map;
+  }
+}
+
+/// A monotonically changing value.
+class Counter extends Metric {
+  Counter(String name, String description)
+      : super(name, description);
+
+  void add(double v) {
+    _value += v;
+  }
+
+  Map _toJSON() {
+    var map = {
+      'type': 'Counter',
+      'id': 'metrics/$_id',
+      'name': name,
+      'description': description,
+      'value': _value,
+    };
+    return map;
+  }
+}
+
+/// Manager of register metrics.
+class Metrics {
+  static int _idCounter = 0;
+  static final List<Metric> _metrics = new List<Metric>();
+
+  static void add(Metric m) {
+    if (m == null) {
+      return;
+    }
+    if (_metrics.contains(m)) {
+      return;
+    }
+    _metrics.add(m);
+  }
+
+  static void remove(Metric m) {
+    _metrics.remove(m);
+  }
+
+  static bool contains(Metric m) {
+    return _metrics.contains(m);
+  }
+
+  static String _printMetric(String id) {
+    for (var i = 0; i < _metrics.length; i++) {
+      var m = _metrics[i];
+      if (m._id == id) {
+        return JSON.encode(m._toJSON());
+      }
+    }
+    return null;
+  }
+
+  static String _printMetrics() {
+    var l = [];
+    for (var i = 0; i < _metrics.length; i++) {
+      var m = _metrics[i];
+      l.add(m._toJSON());
+    }
+    var map = {
+      'type': 'MetricList',
+      'id': 'metrics',
+      'members': l,
+    };
+    return JSON.encode(map);
+  }
+}