Introduce heap snapshot into Memory Dashboard

runtime/observatory/lib/src/elements/memory/snapshot.dart

+// Copyright (c) 2017, 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:async';
+import 'dart:html';
+import 'dart:math' as Math;
+import 'package:observatory/models.dart' as M;
+import 'package:observatory/src/elements/class_ref.dart';
+import 'package:observatory/src/elements/containers/virtual_tree.dart';
+import 'package:observatory/src/elements/helpers/any_ref.dart';
+import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
+import 'package:observatory/src/elements/helpers/tag.dart';
+import 'package:observatory/src/elements/helpers/uris.dart';
+import 'package:observatory/utils.dart';
+
+class MemorySnapshotElement extends HtmlElement implements Renderable {
+  static const tag =
+      const Tag<MemorySnapshotElement>('memory-snapshot', dependencies: const [
+    ClassRefElement.tag,
+    VirtualTreeElement.tag,
+  ]);
+
+  RenderingScheduler<MemorySnapshotElement> _r;
+
+  Stream<RenderedEvent<MemorySnapshotElement>> get onRendered => _r.onRendered;
+
+  M.IsolateRef _isolate;
+  M.EditorRepository _editor;
+  M.HeapSnapshotRepository _snapshots;
+  M.ObjectRepository _objects;
+  M.HeapSnapshot _snapshot;
+  Stream<M.HeapSnapshotLoadingProgressEvent> _progressStream;
+  M.HeapSnapshotLoadingProgress _progress;
+
+  M.IsolateRef get isolate => _isolate;
+
+  factory MemorySnapshotElement(M.IsolateRef isolate, M.EditorRepository editor,
+      M.HeapSnapshotRepository snapshots, M.ObjectRepository objects,
+      {RenderingQueue queue}) {
+    assert(isolate != null);
+    assert(editor != null);
+    assert(snapshots != null);
+    assert(objects != null);
+    MemorySnapshotElement e = document.createElement(tag.name);
+    e._r = new RenderingScheduler(e, queue: queue);
+    e._isolate = isolate;
+    e._editor = editor;
+    e._snapshots = snapshots;
+    e._objects = objects;
+    return e;
+  }
+
+  MemorySnapshotElement.created() : super.created();
+
+  @override
+  attached() {
+    super.attached();
+    _r.enable();
+    _refresh();
+  }
+
+  @override
+  detached() {
+    super.detached();
+    _r.disable(notify: true);
+    children = [];
+  }
+
+  void render() {
+    if (_progress == null) {
+      children = const [];
+      return;
+    }
+    List<HtmlElement> content;
+    switch (_progress.status) {
+      case M.HeapSnapshotLoadingStatus.fetching:
+        content = _createStatusMessage('Fetching snapshot from VM...',
+            description: _progress.stepDescription,
+            progress: _progress.progress);
+        break;
+      case M.HeapSnapshotLoadingStatus.loading:
+        content = _createStatusMessage('Loading snapshot...',
+            description: _progress.stepDescription,
+            progress: _progress.progress);
+        break;
+      case M.HeapSnapshotLoadingStatus.loaded:
+        content = _createReport();
+        break;
+    }
+    children = content;
+  }
+
+  Future reload({bool gc: false}) => _refresh(gc: gc);
+
+  Future _refresh({bool gc: false}) async {
+    _progress = null;
+    _progressStream =
+        _snapshots.get(isolate, roots: M.HeapSnapshotRoots.user, gc: gc);
+    _r.dirty();
+    _progressStream.listen((e) {
+      _progress = e.progress;
+      _r.dirty();
+    });
+    _progress = (await _progressStream.first).progress;
+    _r.dirty();
+    if (M.isHeapSnapshotProgressRunning(_progress.status)) {
+      _progress = (await _progressStream.last).progress;
+      _snapshot = _progress.snapshot;
+      _r.dirty();
+    }
+  }
+
+  static List<Element> _createStatusMessage(String message,
+      {String description: '', double progress: 0.0}) {
+    return [
+      new DivElement()
+        ..classes = ['content-centered-big']
+        ..children = [
+          new DivElement()
+            ..classes = ['statusBox', 'shadow', 'center']
+            ..children = [
+              new DivElement()
+                ..classes = ['statusMessage']
+                ..text = message,
+              new DivElement()
+                ..classes = ['statusDescription']
+                ..text = description,
+              new DivElement()
+                ..style.background = '#0489c3'
+                ..style.width = '$progress%'
+                ..style.height = '15px'
+                ..style.borderRadius = '4px'
+            ]
+        ]
+    ];
+  }
+
+  VirtualTreeElement _tree;
+
+  List<Element> _createReport() {
+    final List roots = _getChildrenDominator(_snapshot.dominatorTree);
+    _tree = new VirtualTreeElement(
+        _createDominator, _updateDominator, _getChildrenDominator,
+        items: roots, queue: _r.queue);
+    if (roots.length == 1) {
+      _tree.expand(roots.first, autoExpandSingleChildNodes: true);
+    }
+    final text = 'In a heap dominator tree, an object X is a parent of '
+        'object Y if every path from the root to Y goes through '
+        'X. This allows you to find "choke points" that are '
+        'holding onto a lot of memory. If an object becomes '
+        'garbage, all its children in the dominator tree become '
+        'garbage as well. '
+        'The retained size of an object is the sum of the '
+        'retained sizes of its children in the dominator tree '
+        'plus its own shallow size, and is the amount of memory '
+        'that would be freed if the object became garbage.';
+    return <HtmlElement>[
+      new DivElement()
+        ..classes = ['content-centered-big', 'explanation']
+        ..text = text
+        ..title = text,
+      _tree
+    ];
+  }
+
+  static Element _createDominator(toggle) {
+    return new DivElement()
+      ..classes = ['tree-item']
+      ..children = [
+        new SpanElement()
+          ..classes = ['size']
+          ..title = 'retained size',
+        new SpanElement()..classes = ['lines'],
+        new ButtonElement()
+          ..classes = ['expander']
+          ..onClick.listen((_) => toggle(autoToggleSingleChildNodes: true)),
+        new SpanElement()
+          ..classes = ['percentage']
+          ..title = 'percentage of heap being retained',
+        new SpanElement()..classes = ['name']
+      ];
+  }
+
+  static const int kMaxChildren = 100;
+  static const int kMinRetainedSize = 4096;
+
+  static _getChildrenDominator(M.HeapSnapshotDominatorNode node) {
+    final list = node.children.toList();
+    list.sort((a, b) => b.retainedSize - a.retainedSize);
+    return list
+        .where((child) => child.retainedSize >= kMinRetainedSize)
+        .take(kMaxChildren);
+  }
+
+  void _updateDominator(
+      HtmlElement element, M.HeapSnapshotDominatorNode node, int depth) {
+    element.children[0].text = Utils.formatSize(node.retainedSize);
+    _updateLines(element.children[1].children, depth);
+    if (_getChildrenDominator(node).isNotEmpty) {
+      element.children[2].text = _tree.isExpanded(node) ? '▼' : '►';
+    } else {
+      element.children[2].text = '';
+    }
+    element.children[3].text =
+        Utils.formatPercentNormalized(node.retainedSize * 1.0 / _snapshot.size);
+    final wrapper = new SpanElement()
+      ..classes = ['name']
+      ..text = 'Loading...';
+    element.children[4] = wrapper;
+    if (node.isStack) {
+      wrapper
+        ..text = ''
+        ..children = [
+          new AnchorElement(href: Uris.debugger(isolate))..text = 'stack frames'
+        ];
+    } else {
+      node.object.then((object) {
+        wrapper
+          ..text = ''
+          ..children = [
+            anyRef(_isolate, object, _objects,
+                queue: _r.queue, expandable: false)
+          ];
+      });
+    }
+    Element.clickEvent
+        .forTarget(element.children[4], useCapture: true)
+        .listen((e) {
+      if (_editor.isAvailable) {
+        e.preventDefault();
+        _sendNodeToEditor(node);
+      }
+    });
+  }
+
+  Future _sendNodeToEditor(M.HeapSnapshotDominatorNode node) async {
+    final object = await node.object;
+    if (node.isStack) {
+      // TODO (https://github.com/flutter/flutter-intellij/issues/1290)
+      // open debugger
+      return new Future.value();
+    }
+    _editor.openObject(_isolate, object);
+  }
+
+  static _updateLines(List<Element> lines, int n) {
+    n = Math.max(0, n);
+    while (lines.length > n) {
+      lines.removeLast();
+    }
+    while (lines.length < n) {
+      lines.add(new SpanElement());
+    }
+  }
+
+  static String rootsToString(M.HeapSnapshotRoots roots) {
+    switch (roots) {
+      case M.HeapSnapshotRoots.user:
+        return 'User';
+      case M.HeapSnapshotRoots.vm:
+        return 'VM';
+    }
+    throw new Exception('Unknown HeapSnapshotRoots');
+  }
+}