Agent does not start in OpenJDK 21 | Unable to make protected final java.lang.Class accessible

[shrinidhi111]

Describe the bug

Upgraded OpenJDK to the latest version, after an internal exercise. Our project works fine but once it was deployed noticed the telemetry did not start

Steps to reproduce

Use the Java instrumentation on docker image openjdk:21-ea-jdk

What did you expect to see?

Telemetry should start

What did you see instead?

auth.1.afb729mhouxe@e2e-75-115    | [otel.javaagent 2023-01-31 10:37:51:695 +0000] [main] INFO io.opentelemetry.javaagent.tooling.VersionLogger - opentelemetry-javaagent - version: 1.22.1
auth.1.afb729mhouxe@e2e-75-115    | OpenTelemetry Javaagent failed to start
auth.1.afb729mhouxe@e2e-75-115    | java.lang.ExceptionInInitializerError
auth.1.afb729mhouxe@e2e-75-115    | 	at io.opentelemetry.javaagent.tooling.muzzle.AgentTooling.<clinit>(AgentTooling.java:22)
auth.1.afb729mhouxe@e2e-75-115    | 	at io.opentelemetry.javaagent.tooling.AgentInstaller.installBytebuddyAgent(AgentInstaller.java:139)
auth.1.afb729mhouxe@e2e-75-115    | 	at io.opentelemetry.javaagent.tooling.AgentInstaller.installBytebuddyAgent(AgentInstaller.java:94)
auth.1.afb729mhouxe@e2e-75-115    | 	at io.opentelemetry.javaagent.tooling.AgentStarterImpl.start(AgentStarterImpl.java:78)
auth.1.afb729mhouxe@e2e-75-115    | 	at io.opentelemetry.javaagent.bootstrap.AgentInitializer.initialize(AgentInitializer.java:35)
auth.1.afb729mhouxe@e2e-75-115    | 	at io.opentelemetry.javaagent.OpenTelemetryAgent.startAgent(OpenTelemetryAgent.java:57)
auth.1.afb729mhouxe@e2e-75-115    | 	at io.opentelemetry.javaagent.OpenTelemetryAgent.premain(OpenTelemetryAgent.java:45)
auth.1.afb729mhouxe@e2e-75-115    | 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
auth.1.afb729mhouxe@e2e-75-115    | 	at java.base/java.lang.reflect.Method.invoke(Method.java:578)
auth.1.afb729mhouxe@e2e-75-115    | 	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:491)
auth.1.afb729mhouxe@e2e-75-115    | 	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndCallPremain(InstrumentationImpl.java:503)
auth.1.afb729mhouxe@e2e-75-115    | Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.findLoadedClass(java.lang.String) accessible: module java.base does not "opens java.lang" to unnamed module @7382f612
auth.1.afb729mhouxe@e2e-75-115    | 	at java.base/java.lang.reflect.AccessibleObject.throwInaccessibleObjectException(AccessibleObject.java:387)
auth.1.afb729mhouxe@e2e-75-115    | 	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:363)
auth.1.afb729mhouxe@e2e-75-115    | 	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:311)
auth.1.afb729mhouxe@e2e-75-115    | 	at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:201)
auth.1.afb729mhouxe@e2e-75-115    | 	at java.base/java.lang.reflect.Method.setAccessible(Method.java:195)
auth.1.afb729mhouxe@e2e-75-115    | 	at io.opentelemetry.javaagent.tooling.muzzle.AgentCachingPoolStrategy.getFindLoadedClassMethod(AgentCachingPoolStrategy.java:114)
auth.1.afb729mhouxe@e2e-75-115    | 	at io.opentelemetry.javaagent.tooling.muzzle.AgentCachingPoolStrategy.<clinit>(AgentCachingPoolStrategy.java:57)
auth.1.afb729mhouxe@e2e-75-115    | 	... 11 more

What version are you using?

1.22.1

Environment

Docker Image : openjdk:21-ea-jdk

Additional context
Add any other context about the problem here.

[laurit]

Byte-buddy doesn't support jdk21 yet. It doesn't detect the jdk version correctly so we skip running some code that would prevent this exception. I guess we could catch this to prevent agent startup from failing but it is hard to predict whether something else would fail later on.

[shrinidhi111]

As of version 1.22.1, which is the highest JDK that it supports? Readme says any Java 8+ application so I assumed any JDK 8+ too

[laurit]

The lates version we currently test with is jdk 19 which is the latest released version.

[shrinidhi111]

Thank you!

[Starefossen]

This still seams to be a problem with applications running java 21

[laurit]

@Starefossen we run tests with java 21 and they work. Please create a new issue, include steps to reproduce.

[maradanasai]

@laurit This still seams to be an issue with jdk 24

docker image: bellsoft/liberica-openjre-debian:24-cds

2025-08-13 13:03:08.347	
Picked up JAVA_TOOL_OPTIONS:  -javaagent:/otel-auto-instrumentation-java-snap-engine/javaagent.jar
2025-08-13 13:03:08.634	
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
2025-08-13 13:03:08.857	
[otel.javaagent 2025-08-13 07:33:08:855 +0000] [main] INFO io.opentelemetry.javaagent.tooling.VersionLogger - opentelemetry-javaagent - version: 1.33.6
2025-08-13 13:03:09.248	
WARNING: A terminally deprecated method in sun.misc.Unsafe has been called
2025-08-13 13:03:09.248	
WARNING: sun.misc.Unsafe::objectFieldOffset has been called by io.opentelemetry.internal.shaded.jctools.util.UnsafeAccess (file:/otel-auto-instrumentation-java-snap-engine/javaagent.jar)
2025-08-13 13:03:09.248	
WARNING: Please consider reporting this to the maintainers of class io.opentelemetry.internal.shaded.jctools.util.UnsafeAccess
2025-08-13 13:03:09.248	
WARNING: sun.misc.Unsafe::objectFieldOffset will be removed in a future release
2025-08-13 13:03:09.427	
OpenTelemetry Javaagent failed to start
2025-08-13 13:03:09.427	
java.lang.ExceptionInInitializerError
2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.tooling.muzzle.AgentTooling.<clinit>(AgentTooling.java:23)
2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.tooling.AgentInstaller.installBytebuddyAgent(AgentInstaller.java:151)
2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.tooling.AgentInstaller.installBytebuddyAgent(AgentInstaller.java:103)

2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.tooling.AgentStarterImpl.start(AgentStarterImpl.java:98)
2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.bootstrap.AgentInitializer$1.run(AgentInitializer.java:53)
2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.bootstrap.AgentInitializer$1.run(AgentInitializer.java:47)
2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.bootstrap.AgentInitializer.execute(AgentInitializer.java:68)
2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.bootstrap.AgentInitializer.initialize(AgentInitializer.java:46)
2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.OpenTelemetryAgent.startAgent(OpenTelemetryAgent.java:57)
2025-08-13 13:03:09.427	
	at io.opentelemetry.javaagent.OpenTelemetryAgent.premain(OpenTelemetryAgent.java:45)
2025-08-13 13:03:09.427	
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(Unknown Source)
2025-08-13 13:03:09.427	
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
2025-08-13 13:03:09.427	
	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndStartAgent(Unknown Source)
2025-08-13 13:03:09.427	
	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndCallPremain(Unknown Source)
2025-08-13 13:03:09.427	
Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.findLoadedClass(java.lang.String) accessible: module java.base does not "opens java.lang" to unnamed module @4909b8da
2025-08-13 13:03:09.427	
	at java.base/java.lang.reflect.AccessibleObject.throwInaccessibleObjectException(Unknown Source)
2025-08-13 13:03:09.427	
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(Unknown Source)
2025-08-13 13:03:09.427	
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(Unknown Source)
2025-08-13 13:03:09.428	
	at java.base/java.lang.reflect.Method.checkCanSetAccessible(Unknown Source)
2025-08-13 13:03:09.428	
	at java.base/java.lang.reflect.Method.setAccessible(Unknown Source)
2025-08-13 13:03:09.428	
	at io.opentelemetry.javaagent.tooling.muzzle.AgentCachingPoolStrategy.getFindLoadedClassMethod(AgentCachingPoolStrategy.java:115)
2025-08-13 13:03:09.428	
	at io.opentelemetry.javaagent.tooling.muzzle.AgentCachingPoolStrategy.<clinit>(AgentCachingPoolStrategy.java:58)
2025-08-13 13:03:09.428	
	... 14 more