Add addViewLoadingTime() public API by MaelNamNam · Pull Request #4180 · DataDog/browser-sdk

MaelNamNam · 2026-02-13T10:27:07Z

Motivation

Allow developers to manually report when a view has finished loading, instead of relying solely on auto-detection. This is needed for complex async loading patterns (e.g., SPAs with deferred data fetching, skeleton screens) where the SDK's heuristic-based auto-detection cannot accurately determine when the view is truly ready.

This brings the Browser SDK to parity with the iOS and Android SDKs which already expose this API.

Changes

Adds a new public API DD_RUM.addViewLoadingTime(options?) that:

Computes loading time as elapsed time since the current view started
Suppresses auto-detected loading time on first manual call
Defaults to first-call-wins semantics; supports { overwrite: true } to replace a previously set value
Handles pre-start buffering (calls before init() are buffered and drained with preserved timestamps)
Emits telemetry usage tracking (addViewLoadingTime feature)
Gracefully no-ops when called on ended/expired views

Files changed:

File	Change
`packages/core/src/domain/telemetry/telemetryEvent.types.ts`	Add `AddViewLoadingTime` to browser telemetry union
`packages/rum-core/src/domain/view/viewMetrics/trackCommonViewMetrics.ts`	`setManualLoadingTime()` with auto-detection suppression
`packages/rum-core/src/domain/view/trackViews.ts`	`addLoadingTime()` on `newView` with overwrite policy
`packages/rum-core/src/boot/startRum.ts`	Wire `addLoadingTime` through `startRumEventCollection`
`packages/rum-core/src/boot/rumPublicApi.ts`	Public API surface, JSDoc, Strategy type, telemetry
`packages/rum-core/src/boot/preStartRum.ts`	Pre-start buffering with timestamp capture

Test instructions

Running tests

# Unit tests
yarn test:unit --spec packages/rum-core/src/domain/view/trackViews.spec.ts
yarn test:unit --spec packages/rum-core/src/boot/rumPublicApi.spec.ts
yarn test:unit --spec packages/rum-core/src/boot/preStartRum.spec.ts

# E2E (requires setup first)
yarn test:e2e:init
yarn test:e2e -g "has a manual loading time"

Checklist

Tested locally
Tested on staging
Added unit tests for this change.
Added e2e/integration tests for this change.
Updated documentation and/or relevant AGENTS.md file

github-actions · 2026-02-13T10:27:22Z

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cit-pr-commenter-54b7da · 2026-02-13T10:28:08Z

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	169.43 KiB	170.24 KiB	+829 B	+0.48%	✅
Rum Profiler	4.29 KiB	4.29 KiB	0 B	0.00%	✅
Rum Recorder	24.54 KiB	24.54 KiB	0 B	0.00%	✅
Logs	56.72 KiB	56.72 KiB	0 B	0.00%	✅
Flagging	944 B	944 B	0 B	0.00%	✅
Rum Slim	126.26 KiB	127.04 KiB	+792 B	+0.61%	✅
Worker	23.63 KiB	23.63 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base CPU Time (ms)	Local CPU Time (ms)	𝚫%
RUM - add global context	0.0045	0.0039	-13.33%
RUM - add action	0.0142	0.0132	-7.04%
RUM - add error	0.0133	0.0128	-3.76%
RUM - add timing	0.0028	0.0025	-10.71%
RUM - start view	0.0134	0.0121	-9.70%
RUM - start/stop session replay recording	0.0007	0.0006	-14.29%
Logs - log message	0.0155	0.0142	-8.39%

🧠 Memory Performance

Action Name	Base Memory Consumption	Local Memory Consumption	𝚫
RUM - add global context	27.68 KiB	27.41 KiB	-276 B
RUM - add action	51.86 KiB	51.63 KiB	-234 B
RUM - add timing	26.47 KiB	25.84 KiB	-644 B
RUM - add error	57.53 KiB	57.67 KiB	+143 B
RUM - start/stop session replay recording	25.70 KiB	24.95 KiB	-768 B
RUM - start view	453.18 KiB	468.65 KiB	+15.46 KiB
Logs - log message	47.21 KiB	46.78 KiB	-443 B

🔗 RealWorld

datadog-datadog-prod-us1 · 2026-02-13T10:29:04Z

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 77.42%
• Overall Coverage: 77.27% (-0.01%)

_{This comment will be updated automatically if new data arrives.

🔗 Commit SHA: 169989b | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

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chatgpt-codex-connector · 2026-02-13T10:32:08Z

packages/rum-core/src/boot/rumPublicApi.ts

+        no_active_view: isResult && 'no_active_view' in result,
+        overwritten: isResult && 'overwritten' in result && result.overwritten !== false,


Default telemetry flags to false for buffered calls

When addViewLoadingTime() is called before init, strategy.addLoadingTime(...) returns undefined, so isResult && ... evaluates to undefined for both no_active_view and overwritten. Those fields are then omitted from the telemetry payload instead of being sent as explicit booleans, which contradicts the AddViewLoadingTime usage schema and makes pre-start telemetry inaccurate. Please coerce these expressions to false when no result is available.

Useful? React with 👍 / 👎.

Add a new public API `DD_RUM.addViewLoadingTime(options?)` that allows developers to manually report when a view has finished loading. - Computes loading time as elapsed time since view start - Suppresses auto-detected loading time on first manual call - First-call-wins by default; `{ overwrite: true }` to replace - Pre-start buffering with preserved call timestamps - Telemetry usage tracking - Gracefully no-ops on ended/expired views - Unit tests + E2E test

thomas-lebeau · 2026-02-13T14:40:34Z

packages/rum-core/src/domain/view/trackViews.ts

    },
+    addLoadingTime(callTimestamp?: TimeStamp, overwrite = false) {
+      if (endClocks) {
+        return { no_active_view: true as const }


🔨 warning: ‏These are not following the standard naming convention. we use camelCase and convert what need to be to pascal_case just before sending the event.

thomas-lebeau · 2026-02-13T14:41:46Z

packages/rum-core/src/domain/view/viewMetrics/trackCommonViewMetrics.ts

+      const hadPreviousManual = isLoadingTimeSetManually
+      const hadAutoValue = !isLoadingTimeSetManually && commonViewMetrics.loadingTime !== undefined
+
+      // Stop auto-detection entirely on first manual call (CONTEXT decision)


❓ question: ‏what does (CONTEXT decision) means?

thomas-lebeau · 2026-02-13T14:42:05Z

packages/rum-core/src/domain/view/viewMetrics/trackCommonViewMetrics.ts

+      isLoadingTimeSetManually = true
+      commonViewMetrics.loadingTime = loadingTime
+
+      // Return overwrite source for Phase 2 telemetry


❓ question: ‏what's Phase 2 telemetry?

thomas-lebeau · 2026-02-13T14:47:03Z

packages/rum-core/src/boot/rumPublicApi.ts

+      addTelemetryUsage({
+        feature: 'addViewLoadingTime',
+        no_view: false,
+        no_active_view: isResult && 'no_active_view' in result,
+        overwritten: isResult && 'overwritten' in result && result.overwritten !== false,
+      })


❓ question: TelemetryUsage is meant to understand which API the customer are using and with which option when available. I don't think we should return run-time analysis like this.

Suggested change

addTelemetryUsage({

feature: 'addViewLoadingTime',

no_view: false,

no_active_view: isResult && 'no_active_view' in result,

overwritten: isResult && 'overwritten' in result && result.overwritten !== false,

})

addTelemetryUsage({

feature: 'addViewLoadingTime',

overwrite

})

thomas-lebeau · 2026-02-13T14:49:42Z

packages/rum-core/src/boot/rumPublicApi.ts

+   * elapsed time since the view started. By default, the first call sets the loading time and
+   * subsequent calls are no-ops. Use `{ overwrite: true }` to replace a previously set value.
+   *
+   * See [Override RUM View Loading Time](https://docs.datadoghq.com/real_user_monitoring/browser/advanced_configuration/) for further information.


🔨 warning: "Override RUM View Loading Time" does not exist at that link ‏

thomas-lebeau · 2026-02-13T14:50:27Z

packages/core/src/domain/telemetry/telemetryEvent.types.ts

 /**
 * Schema of browser specific features usage
 */
+// [MANUAL] AddViewLoadingTime added pending upstream rum-events-format schema sync


❓ question: ‏I did not find any PR related to that in rum-event-format

thomas-lebeau · 2026-02-13T14:54:49Z

packages/rum-core/src/boot/rumPublicApi.ts

+      const result = strategy.addLoadingTime(callTimestamp, options?.overwrite ?? false)
+
+      // For pre-start buffered calls, result is undefined so we emit best-guess default values.
+      const isResult = result && typeof result === 'object'


💬 suggestion: ‏use Types to prevent runtime assertion

MaelNamNam requested a review from a team as a code owner February 13, 2026 10:27

MaelNamNam changed the title ~~✨ feat(rum): add addViewLoadingTime() public API~~ Add addViewLoadingTime() public API Feb 13, 2026

chatgpt-codex-connector bot reviewed Feb 13, 2026

View reviewed changes

MaelNamNam force-pushed the mael.lilensten/manually_report_view_loading_time branch from f4e1030 to 169989b Compare February 13, 2026 10:32

thomas-lebeau reviewed Feb 13, 2026

View reviewed changes

MaelNamNam marked this pull request as draft February 13, 2026 19:10

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Add addViewLoadingTime() public API#4180

Add addViewLoadingTime() public API#4180
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		no_active_view: isResult && 'no_active_view' in result,
		overwritten: isResult && 'overwritten' in result && result.overwritten !== false,

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