High-Scale Java Applications with Virtual Threads: The Future of Efficient Performance

Threads

Threads are a key part of Java that help programs run smoothly and manage multiple tasks at once.?

When you start a Java program, it begins with a “main” thread that controls the flow of the program, stores local variables, and handles errors.?

Threads make it possible to have features like step-by-step control, easy error tracking, and efficient debugging.

Java was one of the first languages to include built-in support for handling many tasks at the same time, called thread-based concurrency.?

This means you can write programs that do several things simultaneously, like handling multiple user requests.?

However, managing threads can be tricky, especially when they share data. This requires careful handling to avoid mistakes and keep the program running fast.

Even though working with threads can be challenging, they are incredibly useful.?

They make sure our programs handle errors well, provide tools to see what each thread is doing, and create an easy-to-follow flow in the code.?

Threads might seem complicated, but they make Java programs more powerful and reliable.

?By understanding and using threads effectively, developers can create high-performing applications that handle multiple tasks seamlessly.

Platform threads

Java’s platform threads, also called OS-managed threads, are the basic unit for running multiple tasks in Java programs.?

These threads are efficient but use a lot of memory, limiting the number you can create.?

This makes it hard to handle millions of tasks at once. Developers often need to either use more hardware or adopt complex programming styles like “async,” which sacrifices ease of debugging and readability.?

Although platform threads simplify development and maintenance, they struggle to scale for large applications due to their heavy resource use, leading to challenges in efficiently managing high volumes of concurrent tasks.

Virtual threads

Virtual threads in Java are a new, lightweight alternative to traditional threads, designed to be more memory-efficient and scalable.?

Unlike regular threads that use large, fixed blocks of memory allocated by the operating system, virtual threads store their stack frames in Java’s garbage-collected heap.?

This approach eliminates the need to estimate the required stack space for each thread, as virtual threads start with a small memory footprint of just a few hundred bytes and automatically adjust as needed.

The operating system only manages platform threads, which serve as the basic unit of scheduling.?

To run code on a virtual thread, the Java runtime mounts it onto a platform thread, known as a carrier thread.?

This involves copying the necessary stack frames from the heap to the carrier thread’s stack temporarily.

?If a virtual thread encounters a blocking operation, it can be unmounted from the carrier thread, freeing the carrier thread to perform other tasks.

This mounting and unmounting process is invisible to Java code, maintaining the consistency of thread identity and behavior.?

Virtual threads can run on multiple carrier threads throughout their lifetime, but to the Java code, they appear as regular threads.

Virtual threads require minimal new API changes, making them easy to integrate into existing Java applications.?

With methods like Thread::ofVirtual for creating virtual threads, they function just like traditional threads, ensuring compatibility and ease of use for developers looking to enhance the scalability and efficiency of their applications.

Here’s a simple example illustrating how virtual threads work in Java:

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class VirtualThreadExample {
public static void main(String[] args) {
// Create an executor service with virtual threads
ExecutorService executor = Executors.newVirtualThreadExecutor();
// Define a task to be executed
Runnable task = () -> {
String threadName = Thread.currentThread().getName();
System.out.println("Executing task on thread: " + threadName);
};
// Submit the task to the executor service
executor.submit(task);
// Shutdown the executor service
executor.shutdown();
}
}        

In this example:

• We create an executor service using Executors.newVirtualThreadExecutor(), which creates an executor service using virtual threads.
• We define a simple task using a lambda expression that prints the name of the current thread.
• We submit the task to the executor service using executor.submit(task).
• Finally, we shutdown the executor service to release its resources using executor.shutdown().

When you run this program, it will execute the task on a virtual thread created by the executor service.?

The virtual thread behaves like a regular thread but uses less memory and can be managed more efficiently by the Java runtime.

Virtual threads do not replace platform threads; they are complementary. However, many server applications will choose virtual threads (often through the configuration of a framework) to achieve greater scalability.

The following example creates 100,000 virtual threads that simulate an IO-bound operation by sleeping for one second. It creates a virtual-thread-per-task executor and submits the tasks as lambdas.

try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
   IntStream.range(0, 100_000).forEach(i -> {
   executor.submit(() -> {
   Thread.sleep(Duration.ofSeconds(1));
   return i;
 });
});
} // close() called implicitly        

Pros of Using Virtual Threads in Java:

Memory Efficiency: Reduced memory usage compared to traditional threads.?

Scalability: Lightweight and efficient for handling large numbers of concurrent tasks.

?Compatibility: Seamless integration with existing Java code and APIs.

Simplicity: Easy to use and behave like regular threads.

Cons of Using Virtual Threads in Java:

Operating System Dependency: Reliance on platform threads provided by the OS.

?Performance Overhead: Potential overhead in managing and coordinating virtual threads.

Limited Control: Less fine-grained control over thread behavior and resource allocation.