blob: 0a666d80084b95806571dca462f4d7a3acb9a275 [file] [log] [blame]
// Copyright 2015 The Chromium Authors. 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 'base/file_system.dart';
import 'base/logger.dart';
import 'base/utils.dart';
import 'build_info.dart';
import 'globals.dart';
import 'vmservice.dart';
// Names of some of the Timeline events we care about.
const String _kFlutterEngineMainEnterEventName = 'FlutterEngineMainEnter';
const String _kFrameworkInitEventName = 'Framework initialization';
const String _kFirstUsefulFrameEventName = 'Widgets completed first useful frame';
class Tracing {
static const String firstUsefulFrameEventName = _kFirstUsefulFrameEventName;
static Future<Tracing> connect(Uri uri) async {
final VMService observatory = await VMService.connect(uri);
return Tracing(observatory);
final VMService vmService;
Future<void> startTracing() async {
await vmService.vm.setVMTimelineFlags(<String>['Compiler', 'Dart', 'Embedder', 'GC']);
await vmService.vm.clearVMTimeline();
/// Stops tracing; optionally wait for first frame.
Future<Map<String, dynamic>> stopTracingAndDownloadTimeline({
bool awaitFirstFrame = false,
}) async {
if (awaitFirstFrame) {
final Status status = logger.startProgress(
'Waiting for application to render first frame...',
timeout: timeoutConfiguration.fastOperation,
try {
final Completer<void> whenFirstFrameRendered = Completer<void>();
(await vmService.onTimelineEvent).listen((ServiceEvent timelineEvent) {
final List<Map<String, dynamic>> events = timelineEvent.timelineEvents;
for (Map<String, dynamic> event in events) {
if (event['name'] == _kFirstUsefulFrameEventName)
bool done = false;
for (FlutterView view in vmService.vm.views) {
if (await view.uiIsolate.flutterAlreadyPaintedFirstUsefulFrame()) {
done = true;
if (!done)
await whenFirstFrameRendered.future;
} catch (exception) {
final Map<String, dynamic> timeline = await vmService.vm.getVMTimeline();
await vmService.vm.setVMTimelineFlags(<String>[]);
return timeline;
/// Download the startup trace information from the given observatory client and
/// store it to build/start_up_info.json.
Future<void> downloadStartupTrace(VMService observatory, { bool awaitFirstFrame = true }) async {
final String traceInfoFilePath = fs.path.join(getBuildDirectory(), 'start_up_info.json');
final File traceInfoFile = fs.file(traceInfoFilePath);
// Delete old startup data, if any.
if (await traceInfoFile.exists())
await traceInfoFile.delete();
// Create "build" directory, if missing.
if (!(await traceInfoFile.parent.exists()))
await traceInfoFile.parent.create();
final Tracing tracing = Tracing(observatory);
final Map<String, dynamic> timeline = await tracing.stopTracingAndDownloadTimeline(
awaitFirstFrame: awaitFirstFrame,
int extractInstantEventTimestamp(String eventName) {
final List<Map<String, dynamic>> events =
List<Map<String, dynamic>>.from(timeline['traceEvents']);
final Map<String, dynamic> event = events.firstWhere(
(Map<String, dynamic> event) => event['name'] == eventName, orElse: () => null,
return event == null ? null : event['ts'];
String message = 'No useful metrics were gathered.';
final int engineEnterTimestampMicros = extractInstantEventTimestamp(_kFlutterEngineMainEnterEventName);
final int frameworkInitTimestampMicros = extractInstantEventTimestamp(_kFrameworkInitEventName);
if (engineEnterTimestampMicros == null) {
printTrace('Engine start event is missing in the timeline: $timeline');
throw 'Engine start event is missing in the timeline. Cannot compute startup time.';
final Map<String, dynamic> traceInfo = <String, dynamic>{
'engineEnterTimestampMicros': engineEnterTimestampMicros,
if (frameworkInitTimestampMicros != null) {
final int timeToFrameworkInitMicros = frameworkInitTimestampMicros - engineEnterTimestampMicros;
traceInfo['timeToFrameworkInitMicros'] = timeToFrameworkInitMicros;
message = 'Time to framework init: ${timeToFrameworkInitMicros ~/ 1000}ms.';
if (awaitFirstFrame) {
final int firstFrameTimestampMicros = extractInstantEventTimestamp(_kFirstUsefulFrameEventName);
if (firstFrameTimestampMicros == null) {
printTrace('First frame event is missing in the timeline: $timeline');
throw 'First frame event is missing in the timeline. Cannot compute startup time.';
final int timeToFirstFrameMicros = firstFrameTimestampMicros - engineEnterTimestampMicros;
traceInfo['timeToFirstFrameMicros'] = timeToFirstFrameMicros;
message = 'Time to first frame: ${timeToFirstFrameMicros ~/ 1000}ms.';
if (frameworkInitTimestampMicros != null)
traceInfo['timeAfterFrameworkInitMicros'] = firstFrameTimestampMicros - frameworkInitTimestampMicros;
printStatus('Saved startup trace info in ${traceInfoFile.path}.');