core: refactor finding of trace start

lighthouse-core/gather/computed/trace-of-tab.js

@@ -82,10 +82,10 @@ class TraceOfTab {
     });
 
     // Find the inspected frame
-    const {startedInPageEvt, frameId} = TracingProcessor.findTracingStartedEvt(keyEvents);
+    const mainFrameIds = TracingProcessor.findMainFrameIds(keyEvents);
 
     // Filter to just events matching the frame ID for sanity
-    const frameEvents = keyEvents.filter(e => e.args.frame === frameId);
+    const frameEvents = keyEvents.filter(e => e.args.frame === mainFrameIds.frameId);
 
     // Our navStart will be the last frame navigation in the trace
     const navigationStart = frameEvents.filter(TraceOfTab.isNavigationStartOfInterest).pop();
@@ -132,10 +132,10 @@ class TraceOfTab {
     // subset all trace events to just our tab's process (incl threads other than main)
     // stable-sort events to keep them correctly nested.
     const processEvents = TraceOfTab
-      .filteredStableSort(trace.traceEvents, e => e.pid === startedInPageEvt.pid);
+      .filteredStableSort(trace.traceEvents, e => e.pid === mainFrameIds.pid);
 
     const mainThreadEvents = processEvents
-      .filter(e => e.tid === startedInPageEvt.tid);
+      .filter(e => e.tid === mainFrameIds.tid);
 
     // traceEnd must exist since at least navigationStart event was verified as existing.
     const traceEnd = trace.traceEvents.reduce((max, evt) => {
@@ -177,7 +177,7 @@ class TraceOfTab {
       timestamps,
       processEvents,
       mainThreadEvents,
-      startedInPageEvt,
+      mainFrameIds,
       navigationStartEvt: navigationStart,
       firstPaintEvt: firstPaint,
       firstContentfulPaintEvt: firstContentfulPaint,

lighthouse-core/lib/traces/tracing-processor.js

@@ -198,39 +198,56 @@ class TraceProcessor {
 
   /**
    * @param {LH.TraceEvent[]} events
-   * @return {{startedInPageEvt: LH.TraceEvent, frameId: string}}
+   * @return {{pid: number, tid: number, frameId: string, ts: number}}
    */
-  static findTracingStartedEvt(events) {
-    /** @type {LH.TraceEvent|undefined} */
-    let startedInPageEvt;
+  static findMainFrameIds(events) {
+    /** @type {number|undefined} */
+    let pid;
+    /** @type {number|undefined} */
+    let tid;
+    /** @type {number|undefined} */
+    let ts;
+    /** @type {string|undefined} */
+    let frameId;
 
     // Prefer the newer TracingStartedInBrowser event first, if it exists
     const startedInBrowserEvt = events.find(e => e.name === 'TracingStartedInBrowser');
     if (startedInBrowserEvt && startedInBrowserEvt.args.data &&
         startedInBrowserEvt.args.data.frames) {
       const mainFrame = startedInBrowserEvt.args.data.frames.find(frame => !frame.parent);
-      const pid = mainFrame && mainFrame.processId;
+      frameId = mainFrame && mainFrame.frame;
+      pid = mainFrame && mainFrame.processId;
+
       const threadNameEvt = events.find(e => e.pid === pid && e.ph === 'M' &&
         e.cat === '__metadata' && e.name === 'thread_name' && e.args.name === 'CrRendererMain');
-      startedInPageEvt = mainFrame && threadNameEvt ?
-        Object.assign({}, startedInBrowserEvt, {
-          pid, tid: threadNameEvt.tid, name: 'TracingStartedInPage',
-          args: {data: {page: mainFrame.frame}}}) :
-        undefined;
+      tid = threadNameEvt && threadNameEvt.tid;
+
+      ts = startedInBrowserEvt.ts;
     }
 
     // Support legacy browser versions that do not emit TracingStartedInBrowser event.
-    if (!startedInPageEvt) {
+    if (!pid || !tid || !frameId || ts === undefined) {
       // The first TracingStartedInPage in the trace is definitely our renderer thread of interest
       // Beware: the tracingStartedInPage event can appear slightly after a navigationStart
-      startedInPageEvt = events.find(e => e.name === 'TracingStartedInPage');
+      const startedInPageEvt = events.find(e => e.name === 'TracingStartedInPage');
+      if (startedInPageEvt && startedInPageEvt.args && startedInPageEvt.args.data) {
+        pid = startedInPageEvt.pid;
+        tid = startedInPageEvt.tid;
+        frameId = startedInPageEvt.args.data.page;
+        ts = startedInPageEvt.ts;
+      }
     }
 
-    if (!startedInPageEvt) throw new LHError(LHError.errors.NO_TRACING_STARTED);
+    if (!pid || !tid || !frameId || ts === undefined) {
+      throw new LHError(LHError.errors.NO_TRACING_STARTED);
+    }
 
-    // @ts-ignore - property chain exists for 'TracingStartedInPage' event.
-    const frameId = /** @type {string} */ (startedInPageEvt.args.data.page);
-    return {startedInPageEvt, frameId};
+    return {
+      pid,
+      tid,
+      frameId,
+      ts,
+    };
   }
 
   /**

lighthouse-core/scripts/lantern/minify-trace.js

@@ -78,11 +78,11 @@ const traceEventsToKeepInProcess = new Set([
  * @param {LH.TraceEvent[]} events
  */
 function filterOutUnnecessaryTasksByNameAndDuration(events) {
-  const {startedInPageEvt} = TracingProcessor.findTracingStartedEvt(events);
+  const {pid} = TracingProcessor.findMainFrameIds(events);
 
   return events.filter(evt => {
     if (toplevelTaskNames.has(evt.name) && evt.dur < 1000) return false;
-    if (evt.pid === startedInPageEvt.pid && traceEventsToKeepInProcess.has(evt.name)) return true;
+    if (evt.pid === pid && traceEventsToKeepInProcess.has(evt.name)) return true;
     return traceEventsToAlwaysKeep.has(evt.name);
   });
 }

lighthouse-core/test/gather/computed/main-thread-tasks-test.js

@@ -14,15 +14,18 @@ const TracingProcessor = require('../../../lib/traces/tracing-processor.js');
 const assert = require('assert');
 
 describe('MainResource computed artifact', () => {
-  const args = {data: {}};
+  const pid = 1;
+  const tid = 2;
+  const frameId = 'BLAH';
+  const args = {data: {}, frame: frameId};
   const baseTs = 1241250325;
   let boilerplateTrace;
 
   beforeEach(() => {
     boilerplateTrace = [
-      {ph: 'I', name: 'TracingStartedInPage', ts: baseTs, args},
-      {ph: 'I', name: 'navigationStart', ts: baseTs, args},
-      {ph: 'R', name: 'firstContentfulPaint', ts: baseTs + 1, args},
+      {ph: 'I', name: 'TracingStartedInPage', pid, tid, ts: baseTs, args: {data: {page: frameId}}},
+      {ph: 'I', name: 'navigationStart', pid, tid, ts: baseTs, args},
+      {ph: 'R', name: 'firstContentfulPaint', pid, tid, ts: baseTs + 1, args},
     ];
   });
 
@@ -60,13 +63,13 @@ describe('MainResource computed artifact', () => {
     */
     const traceEvents = [
       ...boilerplateTrace,
-      {ph: 'X', name: 'TaskA', ts: baseTs, dur: 100e3},
-      {ph: 'B', name: 'TaskB', ts: baseTs + 5e3},
-      {ph: 'X', name: 'TaskC', ts: baseTs + 10e3, dur: 30e3},
-      {ph: 'E', name: 'TaskB', ts: baseTs + 55e3},
+      {ph: 'X', name: 'TaskA', pid, tid, ts: baseTs, dur: 100e3, args},
+      {ph: 'B', name: 'TaskB', pid, tid, ts: baseTs + 5e3, args},
+      {ph: 'X', name: 'TaskC', pid, tid, ts: baseTs + 10e3, dur: 30e3, args},
+      {ph: 'E', name: 'TaskB', pid, tid, ts: baseTs + 55e3, args},
     ];
 
-    traceEvents.forEach(evt => Object.assign(evt, {cat: 'devtools.timeline', args}));
+    traceEvents.forEach(evt => Object.assign(evt, {cat: 'devtools.timeline'}));
 
     const context = {computedCache: new Map()};
     const tasks = await MainThreadTasks.request({traceEvents}, context);
@@ -116,11 +119,11 @@ describe('MainResource computed artifact', () => {
     */
     const traceEvents = [
       ...boilerplateTrace,
-      {ph: 'X', name: 'TaskA', ts: baseTs, dur: 100e3, ...url('about:blank')},
-      {ph: 'B', name: 'TaskB', ts: baseTs + 5e3, ...stackFrames(['urlB.1', 'urlB.2'])},
-      {ph: 'X', name: 'EvaluateScript', ts: baseTs + 10e3, dur: 30e3, ...url('urlC')},
-      {ph: 'X', name: 'TaskD', ts: baseTs + 15e3, dur: 5e3, ...stackFrames(['urlD'])},
-      {ph: 'E', name: 'TaskB', ts: baseTs + 55e3},
+      {ph: 'X', name: 'TaskA', pid, tid, ts: baseTs, dur: 100e3, ...url('about:blank')},
+      {ph: 'B', name: 'TaskB', pid, tid, ts: baseTs + 5e3, ...stackFrames(['urlB.1', 'urlB.2'])},
+      {ph: 'X', name: 'EvaluateScript', pid, tid, ts: baseTs + 10e3, dur: 30e3, ...url('urlC')},
+      {ph: 'X', name: 'TaskD', pid, tid, ts: baseTs + 15e3, dur: 5e3, ...stackFrames(['urlD'])},
+      {ph: 'E', name: 'TaskB', pid, tid, ts: baseTs + 55e3},
     ];
 
     traceEvents.forEach(evt => {

lighthouse-core/test/gather/computed/trace-of-tab-test.js

@@ -27,7 +27,7 @@ describe('Trace of Tab computed artifact:', () => {
       assert.equal(evt.pid, firstEvt.pid, 'A traceEvent is found from another process');
     });
 
-    assert.ok(firstEvt.pid === trace.startedInPageEvt.pid);
+    assert.ok(firstEvt.pid === trace.mainFrameIds.pid);
     assert.ok(firstEvt.pid === trace.navigationStartEvt.pid);
     assert.ok(firstEvt.pid === trace.firstContentfulPaintEvt.pid);
     assert.ok(firstEvt.pid === trace.firstMeaningfulPaintEvt.pid);
@@ -54,7 +54,7 @@ describe('Trace of Tab computed artifact:', () => {
   describe('finds correct FMP', () => {
     it('if there was a tracingStartedInPage after the frame\'s navStart', async () => {
       const trace = await TraceOfTab.compute_(lateTracingStartedTrace);
-      assert.equal(trace.startedInPageEvt.ts, 29343544280);
+      assert.equal(trace.mainFrameIds.ts, 29343544280);
       assert.equal(trace.navigationStartEvt.ts, 29343540951);
       assert.equal(trace.firstContentfulPaintEvt.ts, 29343621005);
       assert.equal(trace.firstMeaningfulPaintEvt.ts, 29344070867);
@@ -63,7 +63,7 @@ describe('Trace of Tab computed artifact:', () => {
 
     it('if there was a tracingStartedInPage after the frame\'s navStart #2', async () => {
       const trace = await TraceOfTab.compute_(badNavStartTrace);
-      assert.equal(trace.startedInPageEvt.ts, 8885435611);
+      assert.equal(trace.mainFrameIds.ts, 8885435611);
       assert.equal(trace.navigationStartEvt.ts, 8885424467);
       assert.equal(trace.firstContentfulPaintEvt.ts, 8886056886);
       assert.equal(trace.firstMeaningfulPaintEvt.ts, 8886056891);
@@ -72,7 +72,7 @@ describe('Trace of Tab computed artifact:', () => {
 
     it('if it appears slightly before the fCP', async () => {
       const trace = await TraceOfTab.compute_(preactTrace);
-      assert.equal(trace.startedInPageEvt.ts, 1805796376829);
+      assert.equal(trace.mainFrameIds.ts, 1805796376829);
       assert.equal(trace.navigationStartEvt.ts, 1805796384607);
       assert.equal(trace.firstContentfulPaintEvt.ts, 1805797263653);
       assert.equal(trace.firstMeaningfulPaintEvt.ts, 1805797262960);
@@ -81,7 +81,7 @@ describe('Trace of Tab computed artifact:', () => {
 
     it('from candidates if no defined FMP exists', async () => {
       const trace = await TraceOfTab.compute_(noFMPtrace);
-      assert.equal(trace.startedInPageEvt.ts, 2146735802456);
+      assert.equal(trace.mainFrameIds.ts, 2146735802456);
       assert.equal(trace.navigationStartEvt.ts, 2146735807738);
       assert.equal(trace.firstContentfulPaintEvt.ts, 2146737302468);
       assert.equal(trace.firstMeaningfulPaintEvt.ts, 2146740268666);
@@ -91,7 +91,7 @@ describe('Trace of Tab computed artifact:', () => {
 
   it('handles traces missing a paints (captured in background tab)', async () => {
     const trace = await TraceOfTab.compute_(backgroundTabTrace);
-    assert.equal(trace.startedInPageEvt.ts, 1966813248134);
+    assert.equal(trace.mainFrameIds.ts, 1966813248134);
     assert.notEqual(trace.navigationStartEvt.ts, 1966813346529, 'picked wrong frame');
     assert.notEqual(trace.navigationStartEvt.ts, 1966813520313, 'picked wrong frame');
     assert.equal(
@@ -158,7 +158,7 @@ describe('Trace of Tab computed artifact:', () => {
         'args': {'name': 'CrRendererMain'},
       }]};
     const trace = await TraceOfTab.compute_(tracingStartedInBrowserTrace);
-    assert.equal(trace.startedInPageEvt.ts, 2193564729582);
+    assert.equal(trace.mainFrameIds.ts, 2193564729582);
     assert.equal(trace.navigationStartEvt.ts, 2193564790059);
   });
 

typings/artifacts.d.ts

@@ -359,8 +359,8 @@ declare global {
         processEvents: Array<TraceEvent>;
         /** The subset of trace events from the page's main thread, sorted by timestamp. */
         mainThreadEvents: Array<TraceEvent>;
-        /** The event marking the start of tracing in the target browser. */
-        startedInPageEvt: TraceEvent;
+        /** Various ids for the current trace context. */
+        mainFrameIds: {pid: number, tid: number, frameId: string, ts: number};
         /** The trace event marking navigationStart. */
         navigationStartEvt: TraceEvent;
         /** The trace event marking firstPaint, if it was found. */