perf(core): [Logs and Metrics Enable Flags 8] Avoid unused Logs worker thread

[adinauer]

PR Stack (Logs and Metrics Enable Flags)

• feat(core): Remove Logs and Metrics enable flags #5939
• feat(logback): [Logs and Metrics Enable Flags 1] Add Logs opt-in #5940
• feat(log4j2): [Logs and Metrics Enable Flags 2] Add Logs opt-in #5941
• feat(jul): [Logs and Metrics Enable Flags 3] Add Logs opt-in #5942
• feat(android): [Logs and Metrics Enable Flags 4] Add Timber Logs opt-in #5943
• feat(android): [Logs and Metrics Enable Flags 5] Add Logcat Logs opt-in #5945
• feat(spring): [Logs and Metrics Enable Flags 6] Add logging Logs opt-in for Spring Boot #5946
• feat(core): [Logs and Metrics Enable Flags 7] Remove Logs enable flag #5947
• perf(core): [Logs and Metrics Enable Flags 8] Avoid unused Logs worker thread #5952
• feat(core): [Logs and Metrics Enable Flags 9] Remove Metrics enable flag #5953
• perf(core): [Logs and Metrics Enable Flags 10] Avoid unused Metrics worker thread #5957
• fix(jul): [Logs and Metrics Enable Flags 11] Preserve null-message records #5960
• docs: [Logs and Metrics Enable Flags 12] Update options guidance #5961
• fix(android): [Logs and Metrics Enable Flags 13] Read Timber option lazily #5964
• ref(logging): [Logs and Metrics Enable Flags 14] Rename Logs opt-ins #5970

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📜 Description

Tracks whether LoggerBatchProcessor has accepted its first Log item. Before that point, empty flushes and restart closes do not schedule processor work. Normal close still closes the executor directly.

After the first accepted item, batching, flushing, and restart-close behavior remain unchanged. Items rejected because of shutdown or queue capacity do not mark the processor as used.

💡 Motivation and Context

The aggregate Logs enable flag has been removed, so every SDK client now owns a logger batch processor. Without this guard, lifecycle flushes—particularly Android background callbacks—can start a worker thread even when the application never captures a Log.

💚 How did you test it?

• ./gradlew :sentry:test :sentry-android-core:testReleaseUnitTest
• ./gradlew spotlessApply apiDump
• Added core tests for construction, empty flush, close, restart close, rejected items, and behavior after first use
• Added an Android background callback test before first use

📝 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.

🔮 Next steps

Remove the aggregate Metrics enable flag.

#skip-changelog

⚠️ Merge this PR using a merge commit (not squash). Only the collection branch is squash-merged into 9.x.x.

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.58.0 (1)	release

⚙️ sentry-android Build Distribution Settings

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	314.02 ms	352.98 ms	38.96 ms
Size	0 B	0 B	0 B

Baseline results on branch: feat/warn-legacy-logs-spring

Startup times

Revision	Plain	With Sentry	Diff
c2e4325	310.06 ms	363.22 ms	53.16 ms

App size

Revision	Plain	With Sentry	Diff
c2e4325	0 B	0 B	0 B

Previous results on branch: perf/logs-batch-thread-first-use

Startup times

Revision	Plain	With Sentry	Diff
31a945a	307.74 ms	351.86 ms	44.11 ms

App size

Revision	Plain	With Sentry	Diff
31a945a	0 B	0 B	0 B

[runningcode]

This seems like a bugfix unrelated to the stack. Can we make this an independent PR?

[adinauer]

This seems like a bugfix unrelated to the stack. Can we make this an independent PR?

Before this PR stack we used noop instances to avoid the thread creation. Since we can't rely on enableLogs / enableMetrics anymore this PR is needed. It's not a separate bugfix but rather an optimization that should be part of the PR stack.