feat: Emit SM on rum response invalid timestamps (#1518)

Author: ellisong

docs/supportability-metrics.md

@@ -159,6 +159,8 @@ A timeslice metric is harvested to the JSE/XHR consumer. An aggregation service
 * Generic/WebDriver/Detected
 <!--- A CSP violation was detected --->
 * Generic/CSPViolation/Detected
+<!-- Invalid timestamp seen in processing RUM response -->
+* Generic/TimeKeeper/InvalidTimestamp/Seen
 
 ### Frameworks
 <!--- React was Detected --->

src/features/page_view_event/aggregate/index.js

@@ -152,9 +152,17 @@ export class Aggregate extends AggregateBase {
     }
 
     try {
+      const wasReady = this.agentRef.runtime.timeKeeper.ready
+
       // will do nothing if already done
       this.agentRef.runtime.timeKeeper.processRumRequest(xhr, this.rumStartTime, rumEndTime, app.nrServerTime)
       if (!this.agentRef.runtime.timeKeeper.ready) throw new Error('TimeKeeper not ready')
+
+      // If timeKeeper's origin time is ahead of nrServerTime, then the timestamp is invalid. Report a supportability metric.
+      const timeDiff = this.agentRef.runtime.timeKeeper.correctedOriginTime - app.nrServerTime
+      if (wasReady && timeDiff > 0) {
+        this.reportSupportabilityMetric('Generic/TimeKeeper/InvalidTimestamp/Seen', timeDiff)
+      }
     } catch (error) {
       this.ee.abort()
       warn(17, error)

tests/components/page_view_event/aggregate.test.js

@@ -30,3 +30,57 @@ test('PageViewEvent does not throw on Harvester driven processes', () => {
     sendEmptyBody: true
   })).toEqual(true) // mimics the manual trigger in PVE `sendRum`; this should return true as it actually tries to "send"
 })
+
+test('PageViewEvent reports SM on invalid timestamp', () => {
+  const spy = jest.spyOn(pveAggregate, 'reportSupportabilityMetric')
+  jest.useFakeTimers()
+
+  mainAgent.runtime.timeKeeper.processRumRequest(undefined, 0, 2, Date.now() + 20000)
+  expect(mainAgent.runtime.timeKeeper.ready).toEqual(true)
+
+  const originTime = mainAgent.runtime.timeKeeper.correctedOriginTime
+  pveAggregate.postHarvestCleanup({
+    status: 200,
+    responseText: JSON.stringify({
+      app: {
+        agents: [{ entityGuid: 'Mjk0MjgxMXxCUk9XU0VSfEFQUExJQ0FUSU9OfDQwNzUwNDQ3NQ' }],
+        // agent's timestamp is in the future, so it is invalid
+        nrServerTime: originTime - 10000
+      }
+    }),
+    xhr: { status: 200 },
+    targetApp: undefined
+  })
+
+  expect(spy).toHaveBeenCalledWith('Generic/TimeKeeper/InvalidTimestamp/Seen', 10000)
+
+  jest.useRealTimers()
+  spy.mockRestore()
+})
+
+test('PageViewEvent does not report SM on valid timestamp', () => {
+  const spy = jest.spyOn(pveAggregate, 'reportSupportabilityMetric')
+  jest.useFakeTimers()
+
+  mainAgent.runtime.timeKeeper.processRumRequest(undefined, 0, 2, Date.now() + 20000)
+  expect(mainAgent.runtime.timeKeeper.ready).toEqual(true)
+
+  const originTime = mainAgent.runtime.timeKeeper.correctedOriginTime
+  pveAggregate.postHarvestCleanup({
+    status: 200,
+    responseText: JSON.stringify({
+      app: {
+        agents: [{ entityGuid: 'Mjk0MjgxMXxCUk9XU0VSfEFQUExJQ0FUSU9OfDQwNzUwNDQ3NQ' }],
+        // agent's timestamp is in the past, so it is valid
+        nrServerTime: originTime + 10000
+      }
+    }),
+    xhr: { status: 200 },
+    targetApp: undefined
+  })
+
+  expect(spy).not.toHaveBeenCalled()
+
+  jest.useRealTimers()
+  spy.mockRestore()
+})