perf(core): Detect Sentry executor thread without a name scan

[runningcode]

Resolves JAVA-607.

Description

PersistingScopeObserver.serializeToDisk decided whether it was already on the Sentry executor thread by scanning the thread name:

if (Thread.currentThread().getName().contains("SentryExecutor")) { ... }

This runs on every scope mutation (breadcrumb, tag, trace, user, …), including on the main thread as the synchronous part of addBreadcrumb. The Thread.getName() + String.contains name scan is pure CPU overhead on that hot path.

This tags the executor threads with a package-private marker Thread subclass (thread name unchanged) and replaces the scan with a cheap SentryExecutorService.isSentryExecutorThread() identity check.

Note: the original rationale claimed this removed a String allocation. On ART, Thread.getName() returns the cached name field without allocating, so the measured win is CPU only (avoiding the scan), not an allocation reduction — see the Benchmark section.

API

Adds one method to the already @ApiStatus.Internal SentryExecutorService; apiDump regenerated (single-line .api addition).

Source

Found via on-device Perfetto method-trace analysis of the Android SDK scope-persistence path (~3,130 scope stores go through this gate). Part of Reduce SDK init time [Android].

🤖 Generated with Claude Code

Benchmark

Measured on-device with androidx Microbenchmark 1.4.1 (benchmark-junit4) on a Samsung Galaxy A55 (SM-A556B), Android API 36 (release build, non-minified).

The benchmark exercises the caller-side cost of a scope mutation with scope persistence enabled (enableScopePersistence = true, cacheDirPath set, no beforeBreadcrumb). The async serialize + disk write is dispatched to a no-op executor so it never runs on the measured thread — mirroring production, where it runs off-thread. Each branch is compared against its base commit (aab952b82e); the per-branch delta isolates this change. allocationCount is deterministic; timeNs has ~±10 ns run-to-run noise on a non-rooted device (unlocked clocks), so it is reported as a median and reproduced across 2 runs.

How it was done

A local, uncommitted androidx microbenchmark module (sentry-android-integration-tests/sentry-uitest-android-microbenchmark) depending on :sentry, with a BenchmarkRule looping the scope mutation. Run with:

./gradlew :sentry-android-integration-tests:sentry-uitest-android-microbenchmark:connectedReleaseAndroidTest \
  -Pandroid.testInstrumentationRunnerArguments.androidx.benchmark.suppressErrors=UNLOCKED

Result

Benchmark	Metric	main	This PR	Delta
setTag	timeNs (median)	~127 ns	~61 ns	~-52%
addBreadcrumb	timeNs (median)	~242 ns	~192 ns	~-20%
both	allocationCount	7 / 3	7 / 3	none

Correction to the original rationale: on ART, Thread.getName() returns the cached name field without allocating a String, so this change does not reduce allocationCount. The win is pure CPU — avoiding the String.contains scan of the thread name on every scope mutation — which is substantial for cheap mutations like setTag (roughly halved). Reproduced across 2 runs.

[linear-code]

JAVA-607

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.47.0 (1)	release

⚙️ sentry-android Build Distribution Settings

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	317.56 ms	361.66 ms	44.10 ms
Size	0 B	0 B	0 B

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
abfcc92	304.04 ms	370.33 ms	66.29 ms
4e3e79d	365.83 ms	477.62 ms	111.79 ms
d8912da	329.94 ms	389.68 ms	59.74 ms
d15471f	294.13 ms	399.49 ms	105.36 ms
abf451a	332.82 ms	403.67 ms	70.85 ms
604a261	380.65 ms	451.27 ms	70.62 ms
806307f	357.85 ms	424.64 ms	66.79 ms
22f4345	307.87 ms	354.51 ms	46.64 ms
d217708	375.27 ms	415.68 ms	40.41 ms
c3ee041	310.64 ms	361.90 ms	51.26 ms

App size

Revision	Plain	With Sentry	Diff
abfcc92	1.58 MiB	2.13 MiB	557.31 KiB
4e3e79d	0 B	0 B	0 B
d8912da	0 B	0 B	0 B
d15471f	1.58 MiB	2.13 MiB	559.54 KiB
abf451a	1.58 MiB	2.20 MiB	635.29 KiB
604a261	1.58 MiB	2.10 MiB	533.42 KiB
806307f	1.58 MiB	2.10 MiB	533.42 KiB
22f4345	1.58 MiB	2.29 MiB	719.83 KiB
d217708	1.58 MiB	2.10 MiB	532.97 KiB
c3ee041	0 B	0 B	0 B