From f6d0dc1931ca881f63152270b9ad0f88743ce71d Mon Sep 17 00:00:00 2001
From: Harrison Healey <harrisonmhealey@gmail.com>
Date: Thu, 20 Jun 2024 12:11:45 -0400
Subject: [PATCH] MM-58772 Change PerformanceReporter to use Date.now for
 timestamps (#27396)

* MM-58772 Change PerformanceReporter to use Date.now for timestamps

* Let timestamps be equal in test
---
 .../performance_telemetry/reporter.test.ts      | 17 ++++++++++++-----
 .../src/utils/performance_telemetry/reporter.ts |  6 +++---
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/webapp/channels/src/utils/performance_telemetry/reporter.test.ts b/webapp/channels/src/utils/performance_telemetry/reporter.test.ts
index ab84e2e96d..c4a1df1e5b 100644
--- a/webapp/channels/src/utils/performance_telemetry/reporter.test.ts
+++ b/webapp/channels/src/utils/performance_telemetry/reporter.test.ts
@@ -33,9 +33,15 @@ describe('PerformanceReporter', () => {
 
         const testMarkA = performance.mark('testMarkA');
         const testMarkB = performance.mark('testMarkB');
+
+        const timeA = Date.now();
         measureAndReport('testMeasureA', 'testMarkA', 'testMarkB');
 
+        await waitForObservations();
+
         const testMarkC = performance.mark('testMarkC');
+
+        const timeBC = Date.now();
         measureAndReport('testMeasureB', 'testMarkA', 'testMarkC');
         measureAndReport('testMeasureC', 'testMarkB', 'testMarkC');
 
@@ -49,26 +55,27 @@ describe('PerformanceReporter', () => {
         expect(sendBeacon.mock.calls[0][0]).toEqual(siteUrl + '/api/v4/client_perf');
         const report = JSON.parse(sendBeacon.mock.calls[0][1]);
         expect(report).toMatchObject({
-            start: performance.timeOrigin + testMarkA.startTime,
-            end: performance.timeOrigin + testMarkB.startTime,
             histograms: [
                 {
                     metric: 'testMeasureA',
                     value: testMarkB.startTime - testMarkA.startTime,
-                    timestamp: performance.timeOrigin + testMarkA.startTime,
                 },
                 {
                     metric: 'testMeasureB',
                     value: testMarkC.startTime - testMarkA.startTime,
-                    timestamp: performance.timeOrigin + testMarkA.startTime,
                 },
                 {
                     metric: 'testMeasureC',
                     value: testMarkC.startTime - testMarkB.startTime,
-                    timestamp: performance.timeOrigin + testMarkB.startTime,
                 },
             ],
         });
+        expect(report.start).toEqual(report.histograms[0].timestamp);
+        expect(report.end).toEqual(report.histograms[2].timestamp);
+        expect(report.histograms[0].timestamp).toBeGreaterThanOrEqual(timeA);
+        expect(report.histograms[0].timestamp).toBeLessThanOrEqual(timeBC);
+        expect(report.histograms[1].timestamp).toBeGreaterThanOrEqual(timeBC);
+        expect(report.histograms[2].timestamp).toBeGreaterThanOrEqual(timeBC);
 
         reporter.disconnect();
     });
diff --git a/webapp/channels/src/utils/performance_telemetry/reporter.ts b/webapp/channels/src/utils/performance_telemetry/reporter.ts
index 6a003a5e86..21d2cde24d 100644
--- a/webapp/channels/src/utils/performance_telemetry/reporter.ts
+++ b/webapp/channels/src/utils/performance_telemetry/reporter.ts
@@ -126,7 +126,7 @@ export default class PerformanceReporter {
         this.histogramMeasures.push({
             metric: Measure.PageLoad,
             value: entries[0].duration,
-            timestamp: performance.timeOrigin + entries[0].startTime,
+            timestamp: Date.now(),
         });
     }
 
@@ -162,7 +162,7 @@ export default class PerformanceReporter {
         this.histogramMeasures.push({
             metric: entry.name,
             value: entry.duration,
-            timestamp: performance.timeOrigin + entry.startTime,
+            timestamp: Date.now(),
         });
     }
 
@@ -187,7 +187,7 @@ export default class PerformanceReporter {
         this.histogramMeasures.push({
             metric: metric.name,
             value: metric.value,
-            timestamp: performance.timeOrigin + performance.now(),
+            timestamp: Date.now(),
         });
     }