GraalVM with Scala: Unlocking High Performance and Polyglot Capabilities

Introduction

GraalVM is a high-performance, open-source runtime that supports multiple languages, including Java, Scala, JavaScript, Python, and more. It is designed to optimize performance, provide ahead-of-time (AOT) compilation, and enable seamless interoperability between different programming languages. In this article, we will explore the benefits of using GraalVM with Scala, how to set it up, and how to leverage its polyglot capabilities.

1. Why GraalVM with Scala?

1.1. Improved Performance

GraalVM offers Just-In-Time (JIT) and AOT compilation techniques, resulting in improved performance compared to traditional JVM implementations. It can generate native executables, enabling faster startup times and reduced memory overhead.

1.2. Polyglot Capabilities

GraalVM allows you to run multiple languages in the same runtime, making it possible to integrate Scala with other languages seamlessly. This polyglot capability opens up new possibilities for building applications that leverage the strengths of different languages.

1.3. Native Image Generation

GraalVM’s native image generation allows you to compile your Scala applications into a standalone executable, eliminating the need for a JVM to run the code. This feature is particularly useful for building lightweight, fast, and container-friendly applications.

2. Setting up GraalVM with Scala

2.1. Downloading GraalVM

Visit the official GraalVM website (https://www.graalvm.org) and download the GraalVM distribution suitable for your operating system. Choose the “JVM-based Languages” distribution, which includes support for Scala.

2.2. Installing GraalVM

Extract the downloaded GraalVM distribution to a directory on your system. Once extracted, navigate to the GraalVM bin directory and set the GraalVM environment variables:

Linux / macOS

export PATH=<path_to_graalvm>/bin:$PATH

Windows (PowerShell)

$env:PATH="<path_to_graalvm>\bin;" + $env:PATH

2.3. Verifying the Installation

To verify that GraalVM is installed correctly, open a terminal and run the following command:

java -version

You should see the GraalVM version being displayed.

3. Running Scala Applications with GraalVM

Now that we have GraalVM set up, let’s see how to run a simple Scala application using GraalVM’s JIT compilation.

3.1. Creating a Scala Application

Create a new file named HelloWorld.scala and add the following code:

object HelloWorld {
  def main(args: Array[String]): Unit = {
    println("Hello, GraalVM with Scala!")
  }
}

3.2. Compiling and Running with GraalVM

To compile and run the Scala application with GraalVM, use the scala command:

scala HelloWorld.scala

You should see the “Hello, GraalVM with Scala!” message printed on the console.

4. Generating a Native Image

GraalVM allows us to compile the Scala application into a native image, which can be executed without relying on the JVM. This process significantly reduces startup time and memory overhead.

4.1. Native Image Compilation

To generate the native image, use the native-image command:

native-image --no-fallback HelloWorld

The --no-fallback flag tells GraalVM not to include the JVM fallback, resulting in a smaller executable.

4.2. Running the Native Image

Once the native image is generated, you can run the application as follows:

Linux / macOS

./helloworld

Windows (Command Prompt)

helloworld

You should see the same “Hello, GraalVM with Scala!” message printed on the console.

5. Polyglot Capabilities with GraalVM

One of the most powerful features of GraalVM is its polyglot capabilities, allowing you to interoperate between different languages seamlessly. Let’s explore an example of integrating Scala and JavaScript.

5.1. Using JavaScript from Scala

Create a new file named PolyglotExample.scala with the following code:

import org.graalvm.polyglot._

object PolyglotExample {
  def main(args: Array[String]): Unit = {
    val context = Context.create()
    val value = context.eval("js", "Math.random()")
    println(s"Random number from JavaScript: $value")
  }
}

5.2. Running the Polyglot Example

Compile and run the PolyglotExample.scala application as we did before:

scala PolyglotExample.scala

You should see a random number generated by JavaScript being printed on the console.

6. Optimizing Scala Applications with GraalVM

GraalVM provides several optimizations to further enhance the performance of Scala applications. Let’s explore some of these optimizations and best practices for optimizing your Scala code with GraalVM.

6.1. Ahead-of-Time Compilation (AOT)

As mentioned earlier, GraalVM offers ahead-of-time (AOT) compilation, which allows you to compile your Scala application to a native image ahead of time. AOT compilation eliminates the need for Just-In-Time (JIT) compilation at runtime, resulting in faster startup times and reduced memory overhead. When targeting AOT compilation, it is essential to ensure that your code does not rely heavily on dynamic class loading or reflection, as these features may not be fully supported in the AOT-compiled code.

6.2. Profile-Guided Optimization (PGO)

GraalVM supports profile-guided optimization (PGO), which involves using the application’s runtime execution profile to guide the optimization process. By collecting runtime profiling data during test runs or real-world usage, you can create a more accurate and optimized native image. To enable PGO, you need to compile your application with profiling enabled and run it with representative inputs to gather the profiling data. Then, recompile the application using the collected profile data to generate the final optimized native image.

6.3. Garbage Collection Tuning

GraalVM offers different garbage collectors to suit different application needs. The default garbage collector, G1, works well for most applications. However, depending on your application’s memory requirements and performance characteristics, you may want to experiment with different garbage collectors and tuning options provided by GraalVM to achieve better performance.

6.4. Custom Runtime Image

GraalVM allows you to create custom runtime images containing only the necessary components for your application. By creating a custom runtime image, you can further reduce the size and startup time of your Scala application. Include only the necessary GraalVM components and native libraries required by your application to optimize the image size.

6.5. Avoiding Unnecessary Dependencies

When using GraalVM, it’s crucial to minimize unnecessary dependencies in your Scala application. GraalVM’s static analysis needs to understand the entire application’s codebase, and excessive dependencies can lead to increased compilation time and larger native image size. Ensure that your application includes only the required dependencies and avoids unused libraries to achieve better performance and reduce image size.

6.6. Profiling and Benchmarking

Regular profiling and benchmarking of your Scala application are essential for identifying performance bottlenecks and verifying the impact of optimizations. Use GraalVM’s built-in profiling tools and external profilers to analyze your application’s performance and fine-tune the optimizations based on profiling data.

7. Conclusion

GraalVM unlocks high performance, polyglot capabilities, and ahead-of-time compilation for Scala applications. By leveraging GraalVM, you can achieve faster startup times, reduced memory overhead, and seamless interoperability with other languages. Additionally, GraalVM’s polyglot capabilities open up new possibilities for building multi-language applications.

In this article, we explored the benefits of using GraalVM with Scala, how to set it up, and how to run Scala applications with both JIT and AOT compilation. We also demonstrated how to leverage GraalVM’s polyglot capabilities by integrating Scala with JavaScript. Moreover, we discussed optimization techniques such as profile-guided optimization, garbage collection tuning, custom runtime images, dependency management, and the importance of profiling and benchmarking.

By adopting GraalVM and applying optimization techniques, you can maximize the performance and efficiency of your Scala applications, providing an enhanced user experience and enabling seamless integration with other languages within the same runtime. Consider incorporating GraalVM into your Scala projects to leverage its power and unlock new possibilities for building high-performance, polyglot applications.