js-java-async-helidon

Asynchronous Polyglot Programming in GraalVM Using Helidon and JavaScript

This is a polyglot Helidon HTTP web service that demonstrates how multiple JavaScript Contexts can be executed in parallel to handle asynchronous operations with Helidon, mixing JavaScript Promise and Java CompletableFuture objects.

Prerequisites

• GraalVM

Preparation

1. Download and install the latest GraalVM JDK using SDKMAN!.

   sdk install java 21.0.1-graal

2. Download or clone the repository and navigate into the js-java-async-helidon directory:

   git clone https://github.com/graalvm/graalvm-demos

   cd graalvm-demos/js-java-async-helidon

3. Build the application using Maven:

   mvn clean package

Now you are all set to run the polyglot Helidon Web service.

Running the Application

You can run this Helidon HTTP web service with the following command:

mvn exec:exec

The application will create a new HTTP web service accepting requests on port 8080. Open http://localhost:8080/greet?request=42 in the browser to send a request.

To demonstrate error handling, the application will not accept requests with request smaller than 42. For example, the following requests will return an error message:

curl http://localhost:8080/greet?request=41
curl http://localhost:8080/greet?request=foo

The Helidon HTTP server uses multiple Java threads. Each thread runs a private JavaScript context. To generate concurrent requests that will be handled by multiple threads, any workload generator can be used. For example, using wrk:

wrk -c 100 -t 10 -d 100 http://localhost:8080/greet?request=42

A Note About the Application

This is a sample application that, for brevity, contains reasonably large snippets of code inside the strings. This is not the best approach for structuring polyglot apps, but the easiest to show in a compact way.