RUM-15702 Add trace sampling decision to DatadogEventBridge by arroz · Pull Request #3495 · DataDog/dd-sdk-android

arroz · 2026-06-02T12:07:31Z

What does this PR do?

With deterministic sampling, the decision of sampling requests on native clients became consistent, based on the sampling rate and session ID. However, when a native client loads an instrumented web site on a WebView, there is a disconnect between the sampling decision used by the browser SDK of the page being viewed in the WebView, and the native client's decision. This cannot be fixed by post-processing on the native client when the data is funneled through it, since the browser SDK needs to know if headers should be injected on requests, or not. More details here (internal).

This is the Android counterpart of DataDog/browser-sdk#4516 and DataDog/dd-sdk-ios#2859.

How?

To fix this problem, this patch introduces a way for Android to obtain the sampling decision from the Browser SDK running on the WebView through the JS bridge. Unlike iOS, this is a simple sync call that obtains the decision from the bridge.

On the JS side, depending on the decision being injected, tracing sample rate will be set to 100 (when the decision is true) or 0 (when it's false). Because of that, the Android SDK re-writes the _dd.rule_psr value with the actual sampling rate configured in the iOS SDK.

Review checklist (to be filled by reviewers)

Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
Make sure you discussed the feature or bugfix with the maintaining team in an Issue
Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

codecov-commenter · 2026-06-02T14:07:30Z

Codecov Report

❌ Patch coverage is 95.12195% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.27%. Comparing base (6c72554) to head (3990aeb).

Files with missing lines	Patch %	Lines
...lin/com/datadog/android/webview/WebViewTracking.kt	50.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3495      +/-   ##
===========================================
+ Coverage    72.21%   72.27%   +0.06%     
===========================================
  Files          965      965              
  Lines        35607    35642      +35     
  Branches      5932     5947      +15     
===========================================
+ Hits         25711    25757      +46     
+ Misses        8279     8274       -5     
+ Partials      1617     1611       -6

Files with missing lines	Coverage Δ
...dog/android/webview/internal/DatadogEventBridge.kt	`100.00% <100.00%> (ø)`
...id/webview/internal/rum/WebViewRumEventConsumer.kt	`92.96% <100.00%> (+0.89%)`	⬆️
...roid/webview/internal/rum/WebViewRumEventMapper.kt	`97.37% <100.00%> (+0.23%)`	⬆️
.../android/webview/internal/rum/WebViewRumFeature.kt	`100.00% <100.00%> (ø)`
...lin/com/datadog/android/webview/WebViewTracking.kt	`84.43% <50.00%> (-1.29%)`	⬇️

... and 37 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

chatgpt-codex-connector

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: e326da0c2a

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

Open a pull request for review
Mark a draft as ready
Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

hamorillo · 2026-06-04T09:28:55Z

+        val rumContext = sdkCore.getFeatureContext(Feature.RUM_FEATURE_NAME, useContextThread = false)
+        val tracingContext = sdkCore.getFeatureContext(Feature.TRACING_FEATURE_NAME, useContextThread = false)


⚠️ I'm a bit worried about these two invocations. Even with useContextThread = false, getFeatureContext acquires a read lock (

dd-sdk-android/dd-sdk-android-core/src/main/kotlin/com/datadog/android/core/internal/DatadogCore.kt

Line 257 in 0901bbb

return@Callable feature.featureContextLock.readLock().safeWithLock {

) on the calling thread.

IIUC getIsTraceSampled() is a @JavascriptInterface method called synchronously from the WebView JS engine, the JS thread will block for the duration of that lock if a concurrent context write is holding the write.

We ran into the same issue in PR #3342 (#3342 (comment)). I would say that we have a similar case here.

Anyway, @0xnm - @satween, can you confirm that what I'm saying is correct?

I agree, I don't think it is a best approach.

WDYT about implementing FeatureContextUpdateReceiver maybe?

WDYT about implementing FeatureContextUpdateReceiver maybe?

Agree, sounds better. We'll need to deal with removeContextUpdateReceiver because DatadogEventBridge doesn't have a lifecycle so we probably need to handle it in a different place but I think that's a better approach.

Addressed this by using WebViewRumFeature as the receiver.

…ple rate.

…text.

hamorillo

Left some minor comments. LGTM overall. I would also wait for @satween's approval, though.

Thanks for the changes!

hamorillo · 2026-06-08T09:50:17Z

+        val tracingContext = webViewRumFeature?.cachedTracingContext.orEmpty()
+
+        val sessionId = (rumContext[SESSION_ID_KEY] as? String)
+            ?.takeIf { rumContext[SESSION_STATE_KEY] == TRACKED_STATE }


❓ I understand that we are adding this guard here to filter the EXPIRED state. However, I don't see any tests covering this. Should we add at least one? Is that the reason for the guard?

hamorillo · 2026-06-08T09:59:17Z

+            latch.await(5, TimeUnit.SECONDS)
+            lastActual = actual
+            if (actual == expectedResult) return
+            Thread.sleep(100)


❓ Do you think we need 100ms? Looks like too much but just checking if there is a reason.

arroz force-pushed the marroz/RUM-15702-add-trace-sampling-decision-to-bridge branch from ca5e54f to 4ebe836 Compare June 2, 2026 12:08

This comment has been minimized.

Sign in to view

arroz changed the title ~~Marroz/rum 15702 add trace sampling decision to bridge~~ RUM-15702 Add trace sampling decision to DatadogEventBridge Jun 2, 2026

arroz marked this pull request as ready for review June 2, 2026 14:57

arroz requested review from a team as code owners June 2, 2026 14:57

chatgpt-codex-connector Bot reviewed Jun 2, 2026

View reviewed changes

Comment thread ...-webview/src/main/kotlin/com/datadog/android/webview/internal/rum/WebViewRumEventConsumer.kt

Comment thread ...id-webview/src/main/kotlin/com/datadog/android/webview/internal/rum/WebViewRumEventMapper.kt

hamorillo reviewed Jun 4, 2026

View reviewed changes

satween reviewed Jun 5, 2026

View reviewed changes

arroz added 9 commits June 5, 2026 13:55

RUM-15702: Initial implementation.

0e17cf7

RUM-15702: Adds multiple tests.

5f72a3e

RUM-15702: Improved consistency on castings obtaining the session sam…

8b71f3c

…ple rate.

RUM-15702: Add rule_psr re-writting tests.

c0db5b3

RUM-15702: Add integration tests.

345abfd

RUM-15702: Style fixes.

b316ce5

RUM-15702: Additional style fix.

e81061c

RUM-15702: Fixed issue from code review: missing tracing in write con…

08e8ab3

…text.

RUM-15702: Avoid locks by caching data in WebViewRumFeature.

3990aeb

arroz force-pushed the marroz/RUM-15702-add-trace-sampling-decision-to-bridge branch from 44a85fb to 3990aeb Compare June 5, 2026 12:55

arroz requested review from 0xnm, hamorillo and satween June 8, 2026 07:33

hamorillo approved these changes Jun 8, 2026

View reviewed changes

satween approved these changes Jun 8, 2026

View reviewed changes

gh-worker-dd-devflow-36fce6 Bot added mergequeue-status: queued mergequeue-status: in_progress and removed mergequeue-status: queued labels Jun 8, 2026

gh-worker-dd-mergequeue-cf854d Bot merged commit befc488 into develop Jun 8, 2026
28 checks passed

gh-worker-dd-devflow-36fce6 Bot removed the mergequeue-status: in_progress label Jun 8, 2026

gh-worker-dd-mergequeue-cf854d Bot deleted the marroz/RUM-15702-add-trace-sampling-decision-to-bridge branch June 8, 2026 15:01

gh-worker-dd-devflow-36fce6 Bot added the mergequeue-status: done label Jun 8, 2026

hamorillo mentioned this pull request Jun 9, 2026

Merge develop into feature/view-update branch #3521

Merged

3 tasks

		val rumContext = sdkCore.getFeatureContext(Feature.RUM_FEATURE_NAME, useContextThread = false)
		val tracingContext = sdkCore.getFeatureContext(Feature.TRACING_FEATURE_NAME, useContextThread = false)

Uh oh!

Conversation

arroz commented Jun 2, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

What does this PR do?

How?

Review checklist (to be filled by reviewers)

Uh oh!

This comment has been minimized.

codecov-commenter commented Jun 2, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Codecov Report

Uh oh!

chatgpt-codex-connector Bot left a comment

Choose a reason for hiding this comment

💡 Codex Review

Uh oh!

Uh oh!

Uh oh!

hamorillo Jun 4, 2026

Choose a reason for hiding this comment

Uh oh!

0xnm Jun 5, 2026

Choose a reason for hiding this comment

Uh oh!

hamorillo Jun 5, 2026

Choose a reason for hiding this comment

Uh oh!

arroz Jun 5, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

hamorillo left a comment

Choose a reason for hiding this comment

Uh oh!

hamorillo Jun 8, 2026

Choose a reason for hiding this comment

Uh oh!

hamorillo Jun 8, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

arroz commented Jun 2, 2026 •

edited

Loading

codecov-commenter commented Jun 2, 2026 •

edited

Loading