Avoid main-thread disk I/O during InstrumenterCustomizerProvider SPI initialization on Android

Description

On Android, the first OpenTelemetry instrumenter construction performs a classpath ServiceLoader lookup for InstrumenterCustomizerProvider.

When this occurs on the main thread with Android StrictMode enabled, it causes a DiskReadViolation.

The lookup path is:

InstrumenterBuilder.build()
→ InternalInstrumenterCustomizerUtil
→ InstrumenterCustomizerUtil.
→ ServiceLoaderUtil.load(...)
→ ServiceLoader
→ ClassLoader.getResources()
→ JarFile / ZipFile
→ disk read

The operation is one-time, but it took approximately 80 ms in our test and violates Android main-thread I/O rules.

Versions

• opentelemetry-instrumentation-api: 2.30.0
• opentelemetry-instrumentation-api-incubator: 2.30.0-alpha
• Android application using StrictMode
• Instrumenter: DefaultHttpClientInstrumenterBuilder

Reproduction

Enable StrictMode before constructing an instrumenter:
Construct the first OpenTelemetry instrumenter.

import android.os.StrictMode;
import com.splunk.rum.instrumentation.okhttp3.OkHttpTelemetry;
import io.opentelemetry.api.OpenTelemetry;

StrictMode.setThreadPolicy(
    new StrictMode.ThreadPolicy.Builder()
        .detectDiskReads()
        .penaltyLog()
        .build());

OkHttpTelemetry telemetry =
    OkHttpTelemetry.builder(OpenTelemetry.noop()).build(); 

The first instrumenter construction produces a DiskReadViolation similar to:

StrictMode policy violation; ~duration=80 ms: android.os.strictmode.DiskReadViolation
	at android.os.StrictMode$AndroidBlockGuardPolicy.onReadFromDisk(StrictMode.java:1658)
	at java.io.UnixFileSystem.getLastModifiedTime(UnixFileSystem.java:289)
	at java.io.File.lastModified(File.java:937)
	at java.util.zip.ZipFile.<init>(ZipFile.java:265)
	at java.util.zip.ZipFile.<init>(ZipFile.java:187)
	at java.util.jar.JarFile.<init>(JarFile.java:169)
	at java.util.jar.JarFile.<init>(JarFile.java:106)
	at libcore.io.ClassPathURLStreamHandler.<init>(ClassPathURLStreamHandler.java:46)
	at dalvik.system.DexPathList$Element.maybeInit(DexPathList.java:750)
	at dalvik.system.DexPathList$Element.findResource(DexPathList.java:777)
	at dalvik.system.DexPathList.findResources(DexPathList.java:572)
	at dalvik.system.BaseDexClassLoader.findResources(BaseDexClassLoader.java:330)
	at java.lang.ClassLoader.getResources(ClassLoader.java:839)
	at java.util.ServiceLoader$LazyIterator.hasNextService(ServiceLoader.java:349)
	at java.util.ServiceLoader$LazyIterator.hasNext(ServiceLoader.java:402)
	at java.util.ServiceLoader$1.hasNext(ServiceLoader.java:488)
	at io.opentelemetry.instrumentation.api.incubator.instrumenter.internal.InstrumenterCustomizerUtil.<clinit>(InstrumenterCustomizerUtil.java:24)
	at java.lang.Class.classForName(Native Method)
	at java.lang.Class.forName(Class.java:454)
	at java.lang.Class.forName(Class.java:379)
	at io.opentelemetry.instrumentation.api.internal.InternalInstrumenterCustomizerUtil.<clinit>(InternalInstrumenterCustomizerUtil.java:22)
	at io.opentelemetry.instrumentation.api.internal.InternalInstrumenterCustomizerUtil.getInstrumenterCustomizerProviders(InternalInstrumenterCustomizerUtil.java:38)
	at io.opentelemetry.instrumentation.api.instrumenter.InstrumenterBuilder.applyCustomizers(InstrumenterBuilder.java:438)
	at io.opentelemetry.instrumentation.api.instrumenter.InstrumenterBuilder.buildInstrumenter(InstrumenterBuilder.java:303)
	at io.opentelemetry.instrumentation.api.instrumenter.InstrumenterBuilder.buildInstrumenter(InstrumenterBuilder.java:295)
	at io.opentelemetry.instrumentation.api.incubator.builder.internal.DefaultHttpClientInstrumenterBuilder.build(DefaultHttpClientInstrumenterBuilder.java:242)

Possible Solutions

Make SPI discovery Android-safe.
Avoid the lookup when no customizer providers are present.
Provide a supported opt-out for Android/library instrumentation.

Note: The customizer SPI was introduced through the instrumenter extension work in
#13917,
which shipped with the 2.19.0 release.

Start with InstrumenterBuilder.applyCustomizers and trace InternalInstrumenterCustomizerUtil, InstrumenterCustomizerUtil, and ServiceLoaderUtil to understand when SPI discovery runs. Reproduce the first DefaultHttpClientInstrumenterBuilder construction with Android StrictMode enabled, then verify the chosen approach avoids the main-thread disk read while preserving customizer-provider discovery.