# Classloader warnings after updating to Java 21 **URL:** \ **Category:** APM\ **Tags:** java\ **Created:** [June 25, 2024, 9:48am UTC](https://discuss.elastic.co/t/classloader-warnings-after-updating-to-java-21/362003 "2024-06-25T09:48:19Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![svenrienstra](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/svenrienstra/32/120748_2.png) [@svenrienstra](https://discuss.elastic.co/u/svenrienstra)\ **Post date:** [June 25, 2024, 9:48am UTC](https://discuss.elastic.co/t/classloader-warnings-after-updating-to-java-21/362003/1 "2024-06-25T09:48:19Z")
After updating our JVM (and updated compile level) from Java 17 to 21 our logs are spammed with classloader warnings. Here is the startup log of the agent: ```auto 2024-06-25 09:24:17,810 [Attach Listener] INFO co.elastic.apm.agent.util.JmxUtils - Found JVM-specific OperatingSystemMXBean interface: com.sun.management.OperatingSystemMXBean 2024-06-25 09:24:17,888 [Attach Listener] INFO co.elastic.apm.agent.util.JmxUtils - Found JVM-specific ThreadMXBean interface: com.sun.management.ThreadMXBean 2024-06-25 09:24:17,918 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - Starting Elastic APM 1.50.0 as *** (0.0.1-SNAPSHOT) on Java 21.0.3 Runtime version: 21.0.3+9-LTS VM version: 21.0.3+9-LTS (Eclipse Adoptium) Linux 6.1.85+ 2024-06-25 09:24:17,919 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - environment: 'NL-DEV' (source: /configuration/elasticapm.properties) 2024-06-25 09:24:17,919 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - config_file: '/configuration/elasticapm.properties' (source: Environment Variables) 2024-06-25 09:24:17,920 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - plugins_dir: '/home/appuser/apm-plugins' (source: Environment Variables) 2024-06-25 09:24:17,920 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - activation_method: 'PROGRAMMATIC_SELF_ATTACH' (source: Attachment configuration) 2024-06-25 09:24:17,920 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - secret_token: 'XXXX' (source: /configuration/elasticapm.properties) 2024-06-25 09:24:17,920 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - server_urls: ' ****' (source: /configuration/elasticapm.properties) 2024-06-25 09:24:17,921 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - application_packages: ' ****' (source: /configuration/elasticapm.properties) 2024-06-25 09:24:17,921 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - profiling_inferred_spans_enabled: 'true' (source: Attachment configuration) 2024-06-25 09:24:17,921 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - profiling_inferred_spans_logging_enabled: 'false' (source: Attachment configuration) 2024-06-25 09:24:17,922 [Attach Listener] INFO co.elastic.apm.agent.configuration.StartupInfo - profiling_inferred_spans_lib_directory: '/home/appuser/' (source: Attachment configuration) 2024-06-25 09:24:27,286 [Attach Listener] INFO co.elastic.apm.agent.bci.bytebuddy.ErrorLoggingListener - org.springframework.web.context.support.GenericWebApplicationContext refers to a missing class. 2024-06-25 09:24:29,011 [Attach Listener] INFO co.elastic.apm.agent.impl.ElasticApmTracer - Tracer switched to RUNNING state 2024-06-25 09:24:29,432 [elastic-apm-server-healthcheck] INFO co.elastic.apm.agent.report.ApmServerHealthChecker - Elastic APM server is available: { "build_date": "2021-12-18T19:59:06Z", "build_sha": "24fe620eeff5a19e2133c940c7e5ce1ceddb1445", "publish_ready": true, "version": "7.16.2"} ``` After that we see this logging every couple of seconds: ```auto [63.187s][warning][jni,resolve] Re-registering of platform native method: jdk.internal.loader.NativeLibraries.load(Ljdk/internal/loader/NativeLibraries$NativeLibraryImpl;Ljava/lang/String;ZZ)Z from code in a different classloader [63.246s][warning][jni,resolve] Re-registering of platform native method: jdk.internal.loader.NativeLibraries.load(Ljdk/internal/loader/NativeLibraries$NativeLibraryImpl;Ljava/lang/String;ZZ)Z from code in a different classloader [68.251s][warning][jni,resolve] Re-registering of platform native method: jdk.internal.loader.NativeLibraries.load(Ljdk/internal/loader/NativeLibraries$NativeLibraryImpl;Ljava/lang/String;ZZ)Z from code in a different classloader [68.298s][warning][jni,resolve] Re-registering of platform native method: jdk.internal.loader.NativeLibraries.load(Ljdk/internal/loader/NativeLibraries$NativeLibraryImpl;Ljava/lang/String;ZZ)Z from code in a different classloader [73.302s][warning][jni,resolve] Re-registering of platform native method: jdk.internal.loader.NativeLibraries.load(Ljdk/internal/loader/NativeLibraries$NativeLibraryImpl;Ljava/lang/String;ZZ)Z from code in a different classloader ``` Turning profiling off (`profiling_inferred_spans_enabled=false`) removes the logging, so it's caused by the profiler. I've already tried setting `profiling_inferred_spans_logging_enabled` to false after finding [WARNING: Install JVM debug symbols to improve profile accuracy · Issue #1789 · elastic/apm-agent-java · GitHub](https://github.com/elastic/apm-agent-java/issues/1789) but that did not help. ---
**Author:** ![Jonas\_Kunz](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jonas_kunz/32/110740_2.png) [@Jonas\_Kunz](https://discuss.elastic.co/u/Jonas_Kunz)\ **Post date:** [June 25, 2024, 10:15am UTC](https://discuss.elastic.co/t/classloader-warnings-after-updating-to-java-21/362003/2 "2024-06-25T10:15:30Z")
Seems related to this JDK issue to me: [https://bugs.openjdk.org/browse/JDK-8239593](https://bugs.openjdk.org/browse/JDK-8239593) Could you try the provided workaround of adding the `-Xlog:jni+resolve=off` jvm command line flag? ---
**Author:** ![svenrienstra](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/svenrienstra/32/120748_2.png) [@svenrienstra](https://discuss.elastic.co/u/svenrienstra)\ **Post date:** [June 25, 2024, 1:38pm UTC](https://discuss.elastic.co/t/classloader-warnings-after-updating-to-java-21/362003/3 "2024-06-25T13:38:51Z")
That does remove the logging. Any idea why this is suddenly necessary with Java 21? ---
**Author:** ![Jonas\_Kunz](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jonas_kunz/32/110740_2.png) [@Jonas\_Kunz](https://discuss.elastic.co/u/Jonas_Kunz)\ **Post date:** [June 26, 2024, 9:56am UTC](https://discuss.elastic.co/t/classloader-warnings-after-updating-to-java-21/362003/4 "2024-06-26T09:56:47Z")
Might be a regression of the linked JDK issue or an intended change of behaviour. I reproduced the issue myself, it started appearing with Java 20, Java 19 was still fine. ---
**Author:** ![Jonas\_Kunz](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jonas_kunz/32/110740_2.png) [@Jonas\_Kunz](https://discuss.elastic.co/u/Jonas_Kunz)\ **Post date:** [June 26, 2024, 10:34am UTC](https://discuss.elastic.co/t/classloader-warnings-after-updating-to-java-21/362003/5 "2024-06-26T10:34:06Z")
I did a bit more investigation on what actually causes the warning: Async-Profiler 1.8.8 (which is used for the inferred spans feature) hooks onto the `NativeLibraries.load` call to detect other JNI-libraries being loaded at runtime. [Here](https://github.com/async-profiler/async-profiler/blob/50fccae0fc2f31368a9e8a8e09fdf607dffe9503/src/profiler.cpp#L684) is the code performing this hooking, which unfortunatley cannot be disabled using any configuration option, so the only remaining option is to silence the warning logs via the option provided earlier.