Initial UI for Metrics in Observatory

runtime/bin/vmservice/observatory/lib/src/service/object.dart

Index: runtime/bin/vmservice/observatory/lib/src/service/object.dart
diff --git a/runtime/bin/vmservice/observatory/lib/src/service/object.dart b/runtime/bin/vmservice/observatory/lib/src/service/object.dart
index 32055de734f4b986228c6f2300ff393a7c887be1..ea40c3c92e515d5453eea4d1e825e34475de643b 100644
--- a/runtime/bin/vmservice/observatory/lib/src/service/object.dart
+++ b/runtime/bin/vmservice/observatory/lib/src/service/object.dart
@@ -76,12 +76,18 @@ abstract class ServiceObject extends Observable {
       case 'Code':
         obj = new Code._empty(owner);
         break;
+      case 'Counter':
+        obj = new Metric._empty(owner);
+        break;
       case 'Error':
         obj = new DartError._empty(owner);
         break;
       case 'Function':
         obj = new ServiceFunction._empty(owner);
         break;
+      case 'Gauge':
+        obj = new Metric._empty(owner);
+        break;
       case 'Isolate':
         obj = new Isolate._empty(owner.vm);
         break;
@@ -697,6 +703,7 @@ class Isolate extends ServiceObjectOwner with Coverage {
     String id = map['id'];
     var obj = _cache[id];
     if (obj != null) {
+      // Consider calling update when map is not a reference.
       return obj;
     }
     // Build the object from the map directly.
@@ -1009,7 +1016,6 @@ class Isolate extends ServiceObjectOwner with Coverage {
   }
 
   Future stepInto() {
-    print('isolate.stepInto');
     return get("debug/resume?step=into").then((result) {
         if (result is DartError) {
           // TODO(turnidge): Handle this more gracefully.
@@ -1038,6 +1044,25 @@ class Isolate extends ServiceObjectOwner with Coverage {
         return isolate.reload();
       });
   }
+
+  final ObservableMap<String, Metric> metrics =
+      new ObservableMap<String, Metric>();
+
+  Future<ObservableMap<String, Metric>> refreshMetrics() {
+    return get('metrics').then((result) {
+      if (result is DartError) {
+        // TODO(turnidge): Handle this more gracefully.
+        Logger.root.severe(result.message);
+      }
+      // Clear metrics map.
+      metrics.clear();
+      // Repopulate metrics map.
+      var members = result['members'];
+      for (var metric in members) {
+        metrics[metric.name] = metric;
+      }
+    });
+  }
 }
 
 /// A [ServiceObject] which implements [ObservableMap].
@@ -1515,7 +1540,7 @@ class ScriptLine extends Observable {
 
   ScriptLine(this.script, this.line, this.text) {
     possibleBpt = !_isTrivialLine(text);
-    
+
     // TODO(turnidge): This is not so efficient.  Consider improving.
     for (var bpt in this.script.isolate.breakpoints['breakpoints']) {
       var bptScript = bpt['location']['script'];
@@ -2193,6 +2218,101 @@ class Socket extends ServiceObject {
   }
 }
 
+class MetricSample {
+  final double value;
+  final DateTime time;
+  MetricSample(this.value) : time = new DateTime.now();
+}
+
+class Metric extends ServiceObject {
+  Metric._empty(ServiceObjectOwner owner) : super._empty(owner) {
+  }
+
+  bool get canCache => true;
+  bool get immutable => false;
+
+  @observable bool recording = false;
+  MetricPoller poller;
+
+  // 8 seconds, 4 seconds, 2 seconds, 1 second, and one hundred milliseconds.
+  static final List<int> pollPeriods = [8000, 4000, 2000, 1000, 100];

[koda, 2014/08/11 16:34:53]

Couldn't you traverse the DOM to get this list instead of hard-coding it?

If you need it, it should be const POLL_PERIODS.

[Cutch, 2014/08/27 22:25:40]

The service library doesn't import dart:html. Also, traversing the DOM requires
waiting for Polymer to "settle" and then traverse- which is heavy. I've moved
this into the MetricsPage (it didn't belong here) but am still not traversing
the DOM.
Done.

+
+  final ObservableList<MetricSample> samples =
+      new ObservableList<MetricSample>();
+  int _sampleBufferSize = 100;
+  int get sampleBufferSize => _sampleBufferSize;
+  set sampleBufferSize(int size) {
+    _sampleBufferSize = size;
+    _removeOld();
+  }
+
+  void addSample(MetricSample sample) {
+    samples.add(sample);
+    _removeOld();
+  }
+
+  void _removeOld() {
+    if (samples.length > _sampleBufferSize) {
+      int count = samples.length - _sampleBufferSize;
+      samples.removeRange(0, count);

[koda, 2014/08/11 16:34:54]

I assume ObservableList is backed by an array? If you have many large buffers,
the quadratic behavior might become costly.

At least remark that using a circular buffer is possible if needed.

[Cutch, 2014/08/27 22:25:40]

Done.

+    }
+  }
+
+  @observable String description;
+  @observable double value = 0.0;
+  @observable double min;
+  @observable double max;
+
+  bool get isGauge => (min != null) && (max != null);

[koda, 2014/08/11 16:34:53]

The fact that 'null' is valid and has this particular meaning should also be
noted on the fields themselves, since it's not obvious (+/-inf would be another
option).

Did you consider having Counter and Gauge subclasses? (Encoding types with
special values is fine if it's internal only, but in this case, it becomes part
of the interface.)

[Cutch, 2014/08/27 22:25:40]

Noted.
Yes, I've considered it and may do this in the future. For now the distinction
is a minor one- proper gauge support will come in a follow up CL and at that
point I may make distinct Counter and Gauge types.

+
+  void _update(ObservableMap map, bool mapIsRef) {
+    name = map['name'];
+    description = map['description'];
+    vmName = map['name'];
+    value = map['value'];
+    min = map['min'];
+    max = map['max'];
+  }
+}
+
+class MetricPoller {
+  // Metrics to be polled.
+  final List<Metric> metrics = new List<Metric>();
+  final int period;

[koda, 2014/08/11 16:34:54]

Redundant? In any case, avoid untyped times (or at least add "Ms" suffix).

[Cutch, 2014/08/27 22:25:40]

Redundant. Removed.

+  final Duration _pollPeriod;
+  Timer _pollTimer;
+
+  MetricPoller(int milliseconds) :
+      period = milliseconds,
+      _pollPeriod = new Duration(milliseconds: milliseconds) {
+    start();
+  }
+
+  void start() {
+    _pollTimer = new Timer.periodic(_pollPeriod, _onPoll);
+  }
+
+  void cancel() {
+    if (_pollTimer != null) {
+      _pollTimer.cancel();
+    }
+    _pollTimer = null;
+  }
+
+  void _onPoll(_) {
+    if (metrics.length == 0) {

[koda, 2014/08/11 16:34:53]

Redundant.

[Cutch, 2014/08/27 22:25:40]

Done.

+      return;
+    }
+    // Reload metrics and add a sample to each.
+    for (var i = 0; i < metrics.length; i++) {

[koda, 2014/08/11 16:34:53]

Use for-in when possible.

[Cutch, 2014/08/27 22:25:40]

Done.

+      var metric = metrics[i];
+      metric.reload().then((m) {
+        m.addSample(new MetricSample(m.value));
+      });
+    }
+  }
+}
+
 // Convert any ServiceMaps representing a null instance into an actual null.
 _convertNull(obj) {
   if (obj is ServiceMap &&