✨ `localStorage` strategy for remote configuration by mormubis · Pull Request #4071 · DataDog/browser-sdk

mormubis · 2026-01-09T16:41:43Z

Motivation

Remote configuration does not support localStorage, which is beneficial for some customers.

Changes

This PR adds the localStorage strategy for remote configuration.

Test instructions

No backend ready for it yet.

Checklist

Tested locally
Tested on staging
Added unit tests for this change.
Added e2e/integration tests for this change.

cit-pr-commenter · 2026-01-09T16:43:30Z

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	169.43 KiB	169.68 KiB	+251 B	+0.14%	✅
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	126.51 KiB	+251 B	+0.19%	✅
Worker	23.63 KiB	23.63 KiB	0 B	0.00%	✅

🚀 CPU Performance

Pending...

🧠 Memory Performance

Pending...

🔗 RealWorld

datadog-datadog-prod-us1 · 2026-01-09T16:44:18Z

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

❄️ 2 New flaky tests detected

cookie getCurrentSite caches the result from Safari 12.1.2 (Mac OS 10.14.6) (Datadog) (Fix with Cursor)
Expected spy cookie to have been called 2 times. It was called 0 times.
<Jasmine>
webpack:///packages/core/src/browser/cookie.spec.ts:46:43 <- /tmp/_karma_webpack_649369/commons.js:37890:49
<Jasmine>
cookie getCurrentSite returns the eTLD+1 for foo.bar.baz.example.com from Safari 12.1.2 (Mac OS 10.14.6) (Datadog) (Fix with Cursor)
Expected 'foo.bar.baz.example.com' to be 'example.com'.
<Jasmine>
webpack:///packages/core/src/browser/cookie.spec.ts:20:61 <- /tmp/_karma_webpack_649369/commons.js:37870:108
<Jasmine>

ℹ️ Info

🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 54.55%
• Overall Coverage: 77.24% (-0.02%)

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

🔗 Commit SHA: d8a54ae | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

mormubis · 2026-01-30T09:16:13Z

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packages/rum-core/src/domain/configuration/remoteConfiguration.types.ts

Add 4 new E2E tests for the localStorage strategy: 1. Basic localStorage retrieval - reads simple string values 2. localStorage with regex extractor - parses extracted values 3. Missing key handling - gracefully falls back when key doesn't exist 4. localStorage unavailable - handles access errors and falls back Tests follow the same pattern as the js strategy tests (PR #3766) and validate: - Synchronous value resolution during SDK initialization - Regex extraction functionality - Fallback behavior for missing or inaccessible keys - Integration with both CDN and npm setups Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

When a remote configuration value fails to resolve (e.g., localStorage key is missing or access fails), the system now preserves the initial configuration fallback value instead of overwriting it with undefined. This fixes the issue where the SDK would lose the fallback version when: - localStorage key is not found - localStorage access throws an error - Any other dynamic resolution returns undefined The fix adds an undefined check before assigning resolved values, ensuring that undefined values do not override the initial configuration. Fixes E2E tests: - should resolve to undefined when localStorage key is missing - should handle localStorage access failure gracefully Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

…ng comment Restore 'electron' union members removed by the submodule bump (unrelated to the localStorage feature) and add a comment explaining the undefined preservation logic in applyRemoteConfiguration. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bcaudan · 2026-02-13T15:19:49Z

packages/rum-core/src/domain/configuration/remoteConfiguration.ts

+      // Skip undefined values to preserve init config fallbacks when any dynamic strategy
+      // (cookie, dom, js, localStorage) fails to resolve.


❓ question: ‏do we have a property for which we want to have this behavior? I may miss something but for now I don't think we can configure a property in init that we can override by a dynamic config.
If we can't really achieve that with current system, I'd be in favor of not adding this fallback and the related tests.

bcaudan · 2026-02-13T15:35:49Z

test/e2e/scenario/rum/remoteConfiguration.scenario.ts

+      expect(initConfiguration.version).toBe('fallback-version')
+    })
+
+  createTest('should handle localStorage access failure gracefully')


👏 praise: ‏nice catch 👍

thomas-lebeau · 2026-02-13T17:20:28Z

packages/rum-core/src/domain/configuration/remoteConfiguration.spec.ts

      it('should resolve to undefined if the cookie is missing', () => {
        expectAppliedRemoteConfigurationToBe(
          { version: { rcSerializedType: 'dynamic', strategy: 'cookie', name: COOKIE_NAME } },
-          { version: undefined }
+          {} // version should not be set when resolution fails


💬 suggestion: ‏Seems that the title could be updated instead of adding a comment

it('should not be set if the cookie is missing', () => {

thomas-lebeau · 2026-02-13T17:22:49Z

packages/rum-core/src/domain/configuration/remoteConfiguration.spec.ts

+        ).toEqual({
+          ...initConfigWithVersion,
+          applicationId: 'yyy',
+          // version should remain 'init-version', not undefined


💬 suggestion: ‏what about making that explicit then, even though it's already implied by ...initConfigWithVersion,:

Suggested change

// version should remain 'init-version', not undefined

version: 'init-version'

mormubis force-pushed the adlrb/remote-config-localstorage branch from 9e8e512 to 94d9a59 Compare January 30, 2026 09:10

DataDog deleted a comment from chatgpt-codex-connector bot Jan 30, 2026

chatgpt-codex-connector bot reviewed Jan 30, 2026

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packages/rum-core/src/domain/configuration/remoteConfiguration.types.ts Show resolved Hide resolved

mormubis changed the title ~~feat: add localStorage strategy to remote config~~ ✨ localStorage strategy for remote configuration Feb 2, 2026

mormubis force-pushed the adlrb/remote-config-localstorage branch from c812560 to a8d262d Compare February 4, 2026 10:01

mormubis and others added 11 commits February 12, 2026 16:02

feat: add localStorage strategy to remote config

e9fc4e9

chore: update schema

8d30519

feat: add schema for localStorage

a3c6e5f

fix: key in schema

6afdd93

empty commit

7e9f5ff

chore: update schema

8fbcb12

chore: update schema

5c0d14a

fix: format

7e4083c

mormubis force-pushed the adlrb/remote-config-localstorage branch from 961a387 to d8a54ae Compare February 12, 2026 15:02

mormubis marked this pull request as ready for review February 13, 2026 14:45

mormubis requested a review from a team as a code owner February 13, 2026 14:45

bcaudan reviewed Feb 13, 2026

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✨ `localStorage` strategy for remote configuration#4071

✨ `localStorage` strategy for remote configuration#4071
mormubis wants to merge 11 commits intomainfrom
adlrb/remote-config-localstorage

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		// Skip undefined values to preserve init config fallbacks when any dynamic strategy
		// (cookie, dom, js, localStorage) fails to resolve.

	// version should remain 'init-version', not undefined
	version: 'init-version'

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