feat(core): Add longTaskIntegration to report JS long tasks as metrics by alwx · Pull Request #6986 · getsentry/sentry-react-native

alwx · 2026-11-04T10:24:08Z

📢 Type of change

Bugfix
New feature
Enhancement
Refactoring

📜 Description

Adds the opt-in longTaskIntegration. It listens to the React Native PerformanceObserver for longtask entries and sends each task of at least minDurationMs (default 200 ms) as the react_native.long_task.duration distribution metric, without an active transaction. sampleRate (default 1) is checked once per app launch, and the integration does nothing where long tasks are not supported (Old Architecture, React Native below 0.82).

💡 Motivation and Context

Stall tracking only records JS thread blocking inside a transaction, so customers cannot see blocking across their fleet. Metrics carry the scope attributes and user from @sentry/core, so apps can filter by their own attributes. Closes #6185.

💚 How did you test it?

Unit tests with a fake PerformanceObserver cover the threshold, sampling, unsupported environments, observe() errors, and disconnect on client close. I have not run it on a device yet.

📝 Checklist

I added tests to verify changes.
No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
I updated the docs if needed.
I updated the wizard if needed.
All tests passing.
Public API changes reviewed by another Mobile SDK team member or implemented according to the develop docs spec.
No breaking changes.

🔮 Next steps

Verify the metric in a sample app on React Native 0.82+ with the New Architecture, and document the integration on docs.sentry.io.

github-actions · 2026-11-04T10:24:32Z

Semver Impact of This PR

⚪ None (no version bump detected)

📋 Changelog Preview

This is how your changes will appear in the changelog.
Entries from this PR are highlighted with a left border (blockquote style).

feat(core): Add longTaskIntegration to report JS long tasks as metrics by alwx and markushi in #6986

feat(ios): Report JS thread hangs as errors (iOS only) by alwx in #6964
chore(deps): update Cocoa SDK to v9.33.0 by github-actions in #6987
feat(profiling): Send Hermes samples as UI profile chunks on Android by alwx in #6966
fix(tracing): Detect expo/fetch behind the Expo Router fetch wrapper by antonis and claude in #6965
ci(release): Bump craft to 3.9.0 and update config by BYK with sentry-junior in #6984
docs(core): Drop stale logger.warn note from AGENTS.md by antonis and claude in #6968
chore(deps): update JavaScript SDK to v10.78.0 by antonis and claude in #6973
chore(deps): Bump getsentry/craft from 2.35.0 to 3.5.0 by alwx in #6983
chore(deps): update Maestro to v2.12.1 by github-actions in #6981
chore(deps): bump getsentry/craft/.github/workflows/changelog-preview.yml from 3.0.0 to 3.4.1 by alwx with dependabot in #6979
chore(deps): bump node-forge from 1.4.0 to 1.4.2 by dependabot in #6982
chore(deps): bump getsentry/github-workflows/validate-pr from 36c729264d2edc29ebae61950c50e1e9f043ad7e to 01bcb7fe69bb48bacd83e675840e3dc95b33c730 by dependabot in #6978
chore(deps): bump ruby/setup-ruby from 1.334.0 to 1.336.0 by dependabot in #6977
chore(deps): bump gradle/actions/setup-gradle from 6.4.0 to 6.4.1 by dependabot in #6976
fix(ios): Honor Sentry.Mask in error screenshots by antonis and claude in #6974
fix(android): Restore enableLogs option mapping by antonis and claude in #6967
chore(deps): update Wizard to v9.1.0 by github-actions in #6972
chore(deps): update Sentry Android Gradle Plugin to v6.25.0 by github-actions in #6971

_{🤖 This preview updates automatically when you update the PR.}

github-actions · 2026-11-04T10:24:48Z

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against d0b151e

Replace the #XXXX placeholder in the CHANGELOG entry with the number of the pull request, #6986, now that the PR exists.

sentry · 2026-11-04T11:02:21Z

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
Sentry RN	io.sentry.reactnative.sample	8.33.0 (113)	Release

⚙️ sentry-react-native Build Distribution Settings

antonis

Left a couple of comments but overall the code changes LGTM 🚀

🔮 Next steps

Verify the metric in a sample app on React Native 0.82+ with the New Architecture, and document the integration on docs.sentry.io.

Let's do that now so that we can test e2e before shipping this and add a link in the description.

lucas-zimerman · 2026-11-04T22:40:15Z

+        return;
+      }
+
+      if (Math.random() >= sampleRate) {


q: Why a sample rate for this metric when metrics by default doesnt have a sample rate?

The issue (#6185) asks for a configurable sample rate. The customer wants this across a large fleet, and the option lets them cut volume and the on-device work. The SDK decides once per launch, so a sampled launch reports all its long tasks, and filtering by user still shows a full picture. The JSDoc says that Sentry does not scale the counts by this rate. Users can also drop metrics in beforeSendMetric, so I can remove the option if we prefer fewer knobs.

lucas-zimerman · 2026-11-04T22:47:12Z

+        return;
+      }
+
+      if (Math.random() >= sampleRate) {


q: would there be any benefit in using import { _INTERNAL_safeMathRandom } from '@sentry/core'; here?

I checked it, and it gives no benefit here. _INTERNAL_safeMathRandom only wraps Math.random() when a framework sets the __SENTRY_SAFE_RANDOM_ID_WRAPPER__ global, which is for server prerendering, for example in Next.js. React Native never sets it so the call is plain Math.random(). The profiling integration in this SDK also uses Math.random() for sampling.

Stall tracking only records JS thread blocking inside an active transaction, so blocking outside of traced work stays invisible. The new opt-in longTaskIntegration listens to the React Native PerformanceObserver for 'longtask' entries and sends each task of at least minDurationMs (default 200 ms) as the react_native.long_task.duration distribution metric. It does not depend on tracing. Scope attributes and the user come from the metrics pipeline in @sentry/core, so apps can filter by their own attributes. sampleRate (default 1) is checked once per launch, so a sampled launch reports all its long tasks. The observer uses buffered: true to also report tasks from before Sentry.init, and disconnects when the client closes. React Native installs PerformanceObserver with 'longtask' support only from 0.82 on the New Architecture, and fixes the native threshold at 50 ms. In other environments the integration logs a debug message and does nothing.

Replace the #XXXX placeholder in the CHANGELOG entry with the number of the pull request, #6986, now that the PR exists.

…ection longTaskIntegration now returns early when enableMetrics is false. @sentry/core already drops the metrics in that case, but the observer still ran on the device for nothing. The support check now runs inside the try/catch. Reading the lazy PerformanceObserver global loads the React Native module, and supportedEntryTypes calls into native code, so both can throw. An error there now logs a debug warning instead of breaking client setup.

antonis

LGTM 👍

Tested with a follow up sample PR #6989 and worked as expected.

markushi

LGTM! Left 2 tiny nits.

Co-authored-by: Markus Hintersteiner <markus.hintersteiner@sentry.io>

* feat(core): Add longTaskIntegration to report JS long tasks as metrics Stall tracking only records JS thread blocking inside an active transaction, so blocking outside of traced work stays invisible. The new opt-in longTaskIntegration listens to the React Native PerformanceObserver for 'longtask' entries and sends each task of at least minDurationMs (default 200 ms) as the react_native.long_task.duration distribution metric. It does not depend on tracing. Scope attributes and the user come from the metrics pipeline in @sentry/core, so apps can filter by their own attributes. sampleRate (default 1) is checked once per launch, so a sampled launch reports all its long tasks. The observer uses buffered: true to also report tasks from before Sentry.init, and disconnects when the client closes. React Native installs PerformanceObserver with 'longtask' support only from 0.82 on the New Architecture, and fixes the native threshold at 50 ms. In other environments the integration logs a debug message and does nothing. * docs(core): Link longTaskIntegration changelog entry to its PR Replace the #XXXX placeholder in the CHANGELOG entry with the number of the pull request, #6986, now that the PR exists. * fix(core): Skip long task observer when metrics are off and guard detection longTaskIntegration now returns early when enableMetrics is false. @sentry/core already drops the metrics in that case, but the observer still ran on the device for nothing. The support check now runs inside the try/catch. Reading the lazy PerformanceObserver global loads the React Native module, and supportedEntryTypes calls into native code, so both can throw. An error there now logs a debug warning instead of breaking client setup. * chore: Add longTaskIntegration to the React Native sample Enable longTaskIntegration with a 100 ms threshold and add a button on the Performance screen that blocks the JS thread for 300 ms, so the react_native.long_task.duration metric can be tested end to end. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> --------- Co-authored-by: Alexander Pantiukhov <alex@apantiukhov.com> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

alwx added a commit that referenced this pull request Nov 4, 2026

docs(core): Link longTaskIntegration changelog entry to its PR

621113e

Replace the #XXXX placeholder in the CHANGELOG entry with the number of the pull request, #6986, now that the PR exists.

alwx marked this pull request as ready for review November 4, 2026 10:50

alwx requested review from a team and lucas-zimerman as code owners November 4, 2026 10:50

alwx requested review from NinjaLikesCheez, antonis, buenaflor, markushi, philprime and runningcode and removed request for a team November 4, 2026 10:50

alwx added the ready-to-merge Triggers the full CI test suite label Nov 4, 2026

antonis reviewed Nov 4, 2026

View reviewed changes

Comment thread packages/core/src/js/integrations/longTask.ts Resolved

antonis reviewed Nov 4, 2026

View reviewed changes

Comment thread packages/core/src/js/integrations/longTask.ts Resolved

antonis reviewed Nov 4, 2026

View reviewed changes

lucas-zimerman reviewed Nov 4, 2026

View reviewed changes

alwx requested review from antonis and lucas-zimerman November 5, 2026 08:42

alwx added 3 commits November 5, 2026 11:24

docs(core): Link longTaskIntegration changelog entry to its PR

8d289e3

Replace the #XXXX placeholder in the CHANGELOG entry with the number of the pull request, #6986, now that the PR exists.

alwx force-pushed the alwx/feature/6185 branch from 52776ac to d30d70a Compare November 5, 2026 10:26

antonis mentioned this pull request Nov 5, 2026

chore: Add longTaskIntegration to the React Native sample #6989

Merged

7 of 11 tasks

antonis approved these changes Nov 5, 2026

View reviewed changes

markushi approved these changes Nov 5, 2026

View reviewed changes

Comment thread packages/core/src/js/integrations/longTask.ts Resolved

Comment thread packages/core/src/js/integrations/longTask.ts Resolved

alwx and others added 2 commits November 5, 2026 13:04

Update packages/core/src/js/integrations/longTask.ts

531ac86

Co-authored-by: Markus Hintersteiner <markus.hintersteiner@sentry.io>

Update packages/core/src/js/integrations/longTask.ts

d0b151e

Co-authored-by: Markus Hintersteiner <markus.hintersteiner@sentry.io>

alwx enabled auto-merge (squash) November 5, 2026 12:05

alwx merged commit c39e39c into main Nov 5, 2026
39 of 76 checks passed

alwx deleted the alwx/feature/6185 branch November 5, 2026 12:07

sentry-release-bot Bot mentioned this pull request Nov 5, 2026

publish: getsentry/sentry-react-native@8.34.0 getsentry/publish#10237

Closed

3 tasks done

github-actions Bot mentioned this pull request Nov 5, 2026

Add standalone long task detection integration #6185

Closed

Navigation Menu

Repository navigation

feat(core): Add longTaskIntegration to report JS long tasks as metrics - #6986

feat(core): Add longTaskIntegration to report JS long tasks as metrics#6986
alwx merged 5 commits into
mainfrom
alwx/feature/6185

alwx commented Nov 4, 2026

Uh oh!

github-actions Bot commented Nov 4, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Nov 4, 2026 •

edited

Loading

Uh oh!

sentry Bot commented Nov 4, 2026 •

edited

Loading

Uh oh!

Uh oh!

Uh oh!

antonis left a comment

Uh oh!

lucas-zimerman Nov 4, 2026

Uh oh!

alwx Nov 5, 2026

Uh oh!

lucas-zimerman Nov 4, 2026

Uh oh!

alwx Nov 5, 2026 •

edited

Loading

Uh oh!

antonis left a comment

Uh oh!

markushi left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Conversation

alwx commented Nov 4, 2026

📢 Type of change

📜 Description

💡 Motivation and Context

💚 How did you test it?

📝 Checklist

🔮 Next steps

Uh oh!

github-actions Bot commented Nov 4, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Semver Impact of This PR

Uh oh!

github-actions Bot commented Nov 4, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

sentry Bot commented Nov 4, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

📲 Install Builds

Android

Uh oh!

Uh oh!

Uh oh!

antonis left a comment

Choose a reason for hiding this comment

🔮 Next steps

Uh oh!

lucas-zimerman Nov 4, 2026

Choose a reason for hiding this comment

Uh oh!

alwx Nov 5, 2026

Choose a reason for hiding this comment

Uh oh!

lucas-zimerman Nov 4, 2026

Choose a reason for hiding this comment

Uh oh!

alwx Nov 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

antonis left a comment

Choose a reason for hiding this comment

Uh oh!

markushi left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

github-actions Bot commented Nov 4, 2026 •

edited

Loading

github-actions Bot commented Nov 4, 2026 •

edited

Loading

sentry Bot commented Nov 4, 2026 •

edited

Loading

alwx Nov 5, 2026 •

edited

Loading