Monday, September 25, 2023

How to Fix java.lang.OutOfMemoryError: Metaspace in Java? [Solution]

Hello guys, An OutOfMemoryError related to Metaspace indicates that your Java application has exhausted the memory allocated for the Metaspace area, which is used for class metadata and method information. This error typically occurs when an application dynamically generates and loads a large number of classes or when the Metaspace size is not properly configured to handle the application's requirements.  Java class metadata (the virtual machine's internal presentation of Java class) is allocated in native memory (referred to here as metaspace). If metaspace for class metadata is exhausted, a java.lang.OutOfMemoryError exception with a detail MetaSpace is thrown. 

The amount of metaspace that can be used for class metadata is limited by the parameter MaxMetaSpaceSize, which is specified on the command line. 

When the amount of native memory needed for a class metadata exceeds MaxMetaSpaceSize, a java.lang.OutOfMemoryError exception with a detail MetaSpace is thrown.

How to deal with java.lang.OutOfMemoryError: Metaspace in Java

To fix this issue, you can take the following steps:

1. Increase Metaspace Size

By default, the Metaspace size is determined by the JVM, but you can adjust it using JVM flags. You can increase the Metaspace size by adding the -XX:MaxMetaspaceSize flag when running your Java application. For example:

$ java -XX:MaxMetaspaceSize=256m -jar YourApplication.jar

This command increases the Metaspace size to 256 megabytes. Adjust the value as needed based on your application's requirements.

If MaxMetaSpaceSize, has been set on the command-line, increase its value. MetaSpace is allocated from the same address spaces as the Java heap. Reducing the size of the Java heap will also make more space available for MetaSpace. 

This is only a correct trade-off if there is an excess of free space in the Java heap.

How to fix java.lang.OutOfMemoryError: Metaspace in Java? [Solution]

2. Review and Optimize Code

Review your application code for any issues that may be causing excessive class loading. This could include unnecessary dynamic class generation or loading classes in a loop unnecessarily. Optimizing your code to reduce class loading can help mitigate Metaspace-related issues.

3. Analyze Classloaders

Sometimes, a memory leak can occur due to classloaders not being garbage collected properly. Ensure that you're managing classloaders correctly, releasing resources when they are no longer needed.

4. Use a Memory Profiler

Consider using a memory profiler tool like VisualVM, YourKit, or Eclipse MAT to analyze memory usage patterns in your application. These tools can help identify memory leaks and provide insights into classloading behavior.

5. Upgrade Your JVM

If you're using an older version of the JVM, consider upgrading to a newer version. Newer JVM versions often come with improvements and optimizations that can help mitigate Metaspace-related issues.

6. Monitor Metaspace Usage

Implement monitoring and alerting for Metaspace usage in your application. This will help you proactively detect and address Metaspace-related problems before they lead to an OutOfMemoryError.

7. Tune Metaspace Settings

Depending on your specific requirements, you may need to fine-tune other Metaspace-related JVM flags such as -XX:MetaspaceSize and -XX:MinMetaspaceFreeRatio. Be cautious when adjusting these settings, as improper values can lead to performance problems or other errors.

8. Consider Class Sharing

If your application repeatedly loads a large number of classes that don't change often, consider using class data sharing (CDS). CDS allows you to precompute and share class metadata across multiple JVM instances, reducing the Metaspace footprint.

9. Profile and Optimize

Use profiling tools to identify and optimize code or libraries that contribute to excessive Metaspace usage. Sometimes, third-party libraries or frameworks may be responsible for excessive class loading.

That's all about how to fix the java.lang.OutOfMemoryError: Metaspace in Java 8 and beyond. By following these steps and properly configuring your JVM settings, you should be able to resolve or mitigate the OutOfMemoryError related to Metaspace in your Java application. It's important to carefully monitor and test these changes to ensure they have the desired effect on your application's performance and stability.

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As per my experience, I strongly suggest experienced Java developers join advanced courses on Java profiling and performance tuning like these JVM and Performance monitoring courses which cover G1 garbage collectors.

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