Nats Graalvm Example

Demonstrating the integration of NATS with GraalVM for creating efficient native executables, showcasing optimal configurations and techniques for leveraging NATS in high-performance, low-footprint applications. This example uses jNats client to connect to the Nats Server which is started within this project.

Requirements

• Graalvm >= 21.0.0 in $JAVA_HOME environment variable

Native Builds

• Maven build native executable (see pom file): ./mvnw clean package -Pnative
• CLI minimal ( replace your-application-classpath):

    native-image \
    --initialize-at-run-time=io.nats.client.support.RandomUtils \
    --initialize-at-run-time=java.security.SecureRandom \
    -H:Name=native-executable \
    -cp your-application-classpath berlin.yuna.nativeexample.Main

• CLI strict ( replace your-application-classpath):

    native-image \
    --no-fallback \
    --no-server \
    --initialize-at-build-time \
    --initialize-at-run-time=io.nats.client.support.RandomUtils \
    --initialize-at-run-time=java.security.SecureRandom \
    -H:Name=native-executable \
    -cp your-application-classpath berlin.yuna.nativeexample.Main

GraalVM parameter explanation

Parameter	Description
--no-fallback	Disables the fallback feature, ensuring that the native image doesn't include the JVM. This results in a smaller, more efficient executable but requires all code to be fully native-image compatible.
--initialize-at-build-time	Instructs GraalVM to initialize specified classes at build time rather than at runtime. This can improve startup time but requires careful management of class initialization to avoid errors.
--initialize-at-run-time=io.nats.client.support.RandomUtils	Specifies that the io.nats.client.support.RandomUtils class should be initialized at runtime. This is needed because this class likely uses or initializes Random or SecureRandom instances in static fields. Static initialization at build time would cause these instances to have a fixed seed and not behave as expected at runtime, reducing randomness and potentially affecting the security or functionality of the application.
--initialize-at-run-time=java.security.SecureRandom	Indicates that the java.security.SecureRandom class should be initialized at runtime. SecureRandom is used for cryptographic operations and relies on entropy sources that are only available at runtime. Initializing it at build time would result in a lack of proper randomness as the entropy sources would not be properly utilized, potentially compromising security.
-H:Name=native-executable	Sets the name of the generated executable file.
-cp "<class-path>"	Specifies the classpath, which includes paths to all classes and libraries that your application depends on. Separate multiple paths with : on Unix-like systems or ; on Windows.
<main-class>	The fully qualified name of your main class. This is the entry point of your application.