How to Resolve java.lang.OutOfMemoryError: Unable to Create New Native Thread

What does the error java.lang.OutOfMemoryError: unable to create new native thread mean and how can it be fixed?

The error `java.lang.OutOfMemoryError: unable to create new native thread` occurs in Java applications when the Java Virtual Machine (JVM) is unable to allocate a new thread due to resource limitations. This can happen if the application has reached its maximum thread limit or if the system resources (like memory or file descriptors) are exhausted.

// Example of using ThreadPoolExecutor for better thread management
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ThreadPoolExample {
    public static void main(String[] args) {
        int numberOfThreads = 10;
        ExecutorService executor = Executors.newFixedThreadPool(numberOfThreads);
        for (int i = 0; i < 100; i++) {
            executor.submit(new Task()); // Submit tasks to the pool
        }
        executor.shutdown(); // Shutdown the executor
    }
}
class Task implements Runnable {
    public void run() {
        System.out.println("Thread: " + Thread.currentThread().getName());
    }
}

Causes

• Exceeding the maximum number of threads allowed by the operating system.
• Running out of system memory that restricts thread creation.
• Resource leaks that lead to unnecessary thread holding.
• Improper thread pooling or thread management.

Solutions

• Increase the maximum number of threads allowed by the operating system, which can usually be configured in system settings.
• Optimize thread usage in the application to ensure that threads are properly managed and reused instead of created and discarded.
• Check and increase the maximum heap size using the JVM options `-Xms` and `-Xmx`. For example: `java -Xms512m -Xmx2048m YourApplication`.
• Utilize thread pools or Executors in Java to manage a limited number of threads efficiently.

Mistake: Not monitoring thread usage which can lead to blind scaling.

Solution: Use profiling tools (like VisualVM or Java Mission Control) to monitor the thread usage of your application.

Mistake: Forgetting to shutdown threads leading to memory leaks.

Solution: Always ensure that you properly shutdown executors or thread pools to free up resources.

Mistake: Setting thread limits too high without resource planning.

Solution: Evaluate your server's hardware specifications and set thread limits accordingly.