ref(android): Measure ANR thresholds on the monotonic clock (JAVA-579) by runningcode · Pull Request #6041 · getsentry/sentry-java

runningcode · 2026-09-02T08:32:57Z

📜 Description

Moves the ANR integrations to use the MonotonicTicker abstraction. This also makes them more testable since we aren't hard coding a direct access to SystemClock.

A note: We previously used SystemClock.uptimeMillis which does not include time spent in sleep. The implementation of MonotonicTicker on Android uses SystemClock.elapsedRealtimeNanos(). ANRWatchDog polls in the background too, so right after the device wakes up the deadline can already have passed. That doesn't produce a false ANR: the watchdog only reports when ActivityManager also lists the process as NOT_RESPONDING. The cost is one extra getProcessesInErrorState() call after a wake-up. AnrProfilingIntegration only polls in the foreground and resets its reading on foreground.

Also ANRWatchdog was previously using a ICurrentDateProvider. Which has two different implementations, a wall clock and a monotonic clock. It happens to work by chance on Android because on Android it should always return a monotonic clock but this is quite brittle.

💡 Motivation and Context

Fixing clocks and making the code more sane.

resolves: JAVA-579

💚 How did you test it?

./gradlew :sentry-android-core:testReleaseUnitTest :sentry:checkKotlinAbi — green.

📝 Checklist

I added GH Issue ID & Linear ID
I added tests to verify the 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.
Review from the native team if needed.
No breaking change or entry added to the changelog.
No breaking change for hybrid SDKs or communicated to hybrid SDKs.
Public API changes reviewed by another Mobile SDK team member or implemented according to the develop docs spec.

linear-code · 2026-09-02T08:33:01Z

JAVA-579

sentry · 2026-09-02T08:36:17Z

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.63.0 (1)	release

⚙️ sentry-android Build Distribution Settings

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The ANR tests advance the ticker from the test thread while the watchdog thread reads it, which without volatile is a data race that can leave the watchdog looking at a stale tick forever.

The watchdog took its readings from an ICurrentDateProvider lambda over SystemClock.uptimeMillis(). The type named no clock, so a call site could not tell what it was measuring, and the arithmetic -- now minus the last tick, compared against a threshold -- was spelled out inline. MonotonicClock and Deadline replace both: the clock is a named type, and the watchdog asks the question it actually cares about, which is whether the main thread has missed its window. The clock counts deep sleep, which uptimeMillis() did not, so a suspend between posting the ticker and checking it now looks like a missed window. It cannot fabricate an ANR: the watchdog reports only once ActivityManager confirms the process is NOT_RESPONDING, and on resume the main thread runs the ticker that is already queued.

Same reasoning as the watchdog: the suspicion and ANR thresholds are now read from a named clock rather than SystemClock, and injecting it lets the tests drive it directly instead of going through Robolectric's shadow clock. Deep sleep cannot inflate the measurement here either, because the polling thread parks itself while the app is backgrounded and resets the baseline when it wakes.

…A-579) Both ANR detectors resolved AndroidMonotonicTicker.getInstance() themselves, so each call site named the concrete Android ticker and neither could be pointed at another one. SentryAndroidOptions already knows which ticker the platform wants, but it is final, so a test cannot override the getter. Add a one-method MonotonicTickerProvider that SentryOptions implements. ANRWatchDog gains a static factory that reads its timeout, debug behavior, logger and ticker off options, replacing the telescoping convenience constructor. AnrProfilingIntegration installs the ticker in register(), which drops the two constructors it had grown and leaves the public no-arg constructor and sentry-android-core.api unchanged. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Drop the JavaMonotonicTicker fallback. On Android nanoTime() stops while the device is suspended, so a default that is never meant to be used would measure main-thread stalls against the wrong clock if it ever were. Start the test ticker at a non-zero origin. A fake that starts at zero makes a reading taken against a different origin indistinguishable from a correct one, which is the mistake this whole change exists to prevent. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

MonotonicTickerProvider only existed so a test could hand AnrProfilingIntegration a fake ticker. A package-private method taking the ticker does the same without a new core interface or a change to the SentryOptions supertype. Also rename the ANRWatchDog test that claimed to cover a device suspend: the Android ticker counts suspend, so the test only shows the threshold is measured on the injected ticker rather than wall time. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Tests spy SentryAndroidOptions to supply a TestMonotonicTicker, so the package-private installTicker seam is no longer needed. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

… (JAVA-579) Error Prone does not run on sentry-android-core, so the suppression had no effect. The lambda field stays: removeCallbacks matches the posted Runnable by identity. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

markushi

LGTM!

9.x.x left ANRWatchDog.monotonicTicker (#6041) and AndroidContinuousProfiler.buildInfoProvider (#6518) without readers, which Error Prone reports as UnusedVariable. The constructors keep their parameters, so their signatures don't change. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

- ANRWatchDog.monotonicTicker is never read (#6041), since the ticker lambda captures the constructor parameter. Remove the field and keep the parameter. - ActivityFramesTracker.lock is protected in a final class; make it package-private. - LifecycleWatcher reads the session start Date to seed the session window; suppress JavaUtilDate there, as the other Date uses are. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

@OverRide

* ref(android): Fix Error Prone warnings in sentry-android-core Error Prone never ran on sentry-android-core. Enabling it reports 59 warnings outside Javadoc, which fail the build under -Werror. - Suppress FutureReturnValueIgnored, JavaUtilDate, and ReferenceEquality where identity is intended, as the sentry module does. - Keep the AnrProfilingIntegration updater a field, since removeCallbacks needs the instance that was posted, and suppress UnnecessaryLambda there. - Read the ANR thread dump and the app start profiling config as UTF-8, Android's default charset. - Remove unused fields and parameters, add missing @OverRide, make long-to-double conversions explicit, and narrow members that are effectively private or protected in a final class. - Explain the two catch blocks that ignore their exception. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * ref(android): Fix the Error Prone warnings only main has - ANRWatchDog.monotonicTicker is never read (#6041), since the ticker lambda captures the constructor parameter. Remove the field and keep the parameter. - ActivityFramesTracker.lock is protected in a final class; make it package-private. - LifecycleWatcher reads the session start Date to seed the session window; suppress JavaUtilDate there, as the other Date uses are. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * ref(android): Keep the default charset reads as they were Android's default charset is always UTF-8, so DefaultCharset is disabled for the Android modules in #6493 instead of being fixed here. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * ref(android): Drop the UnnecessaryLambda suppressions #6493 disables UnnecessaryLambda for the Android modules, so the suppressions on the ANRWatchDog and AnrProfilingIntegration fields are redundant. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * ref(android): Drop the updater field comment Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * docs(android): Make the local-class method comment a plain comment Error Prone's NotJavadoc flags Javadoc on methods of local classes, which #6537 added in AndroidConnectionStatusProvider. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

runningcode force-pushed the no/java-576-checkin-stopwatch branch from edd22f0 to fef63c7 Compare September 2, 2026 13:35

runningcode force-pushed the no/java-579-anr-uptime-clock branch from cabb812 to 77eb8c9 Compare September 2, 2026 13:35

runningcode force-pushed the no/java-576-checkin-stopwatch branch from fef63c7 to 9829cc8 Compare September 2, 2026 13:37

runningcode force-pushed the no/java-579-anr-uptime-clock branch from 77eb8c9 to 2065803 Compare September 2, 2026 13:37

runningcode force-pushed the no/java-576-checkin-stopwatch branch from 9829cc8 to c11fec4 Compare September 3, 2026 15:11

runningcode force-pushed the no/java-579-anr-uptime-clock branch from 2065803 to 498932f Compare September 3, 2026 15:11

runningcode changed the title ~~ref(android): Measure ANR thresholds on the uptime clock (JAVA-579)~~ ref(android): Measure ANR thresholds on the monotonic clock (JAVA-579) Sep 3, 2026

runningcode force-pushed the no/java-576-checkin-stopwatch branch from c11fec4 to 0d1d4c9 Compare September 3, 2026 15:41

runningcode force-pushed the no/java-579-anr-uptime-clock branch from 498932f to ae9d046 Compare September 3, 2026 15:41

runningcode force-pushed the no/java-576-checkin-stopwatch branch from 0d1d4c9 to 6861150 Compare September 4, 2026 08:57

runningcode force-pushed the no/java-579-anr-uptime-clock branch from ae9d046 to 46f3c83 Compare September 4, 2026 08:58

runningcode mentioned this pull request Sep 4, 2026

[DO NOT MERGE] feat(time): Anchor span timestamps on one wall-clock reading (JAVA-572) #6055

Closed

runningcode force-pushed the no/java-576-checkin-stopwatch branch from 6861150 to b35959c Compare September 4, 2026 15:11

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runningcode commented Sep 11, 2026

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Comment thread sentry-android-core/src/main/java/io/sentry/android/core/ANRWatchDog.java Resolved

runningcode force-pushed the no/java-579-anr-uptime-clock branch from 50973fd to fd94017 Compare September 11, 2026 15:19

runningcode marked this pull request as ready for review September 11, 2026 15:21

runningcode requested review from 0xadam-brown, adinauer, markushi and romtsn as code owners September 11, 2026 15:21

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Comment thread sentry-android-core/src/main/java/io/sentry/android/core/ANRWatchDog.java Resolved

runningcode added the sanity-check PR needs a lightweight review for obvious issues label Sep 11, 2026

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Comment thread sentry-android-core/src/main/java/io/sentry/android/core/anr/AnrProfilingIntegration.java Resolved

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Comment thread sentry-android-core/src/main/java/io/sentry/android/core/anr/AnrProfilingIntegration.java Resolved

runningcode and others added 8 commits November 6, 2026 12:44

test(time): Publish the TestMonotonicTicker tick to other threads

7b33db5

The ANR tests advance the ticker from the test thread while the watchdog thread reads it, which without volatile is a data race that can leave the watchdog looking at a stale tick forever.

changelog

c4e0e26

ref(android): Read the ANR profiling ticker from options (JAVA-579)

f05669b

Tests spy SentryAndroidOptions to supply a TestMonotonicTicker, so the package-private installTicker seam is no longer needed. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

runningcode force-pushed the no/java-579-anr-uptime-clock branch from 84203d1 to f05669b Compare November 6, 2026 11:48

markushi approved these changes Nov 6, 2026

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runningcode merged commit 3d1f55e into main Nov 6, 2026
43 of 44 checks passed

runningcode deleted the no/java-579-anr-uptime-clock branch November 6, 2026 12:22

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ref(android): Measure ANR thresholds on the monotonic clock (JAVA-579) - #6041

ref(android): Measure ANR thresholds on the monotonic clock (JAVA-579)#6041
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📜 Description

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