Spring native build not using virtual threads

Question

I'm building some simple web applications where I want to take advantage of both native compilation and virtual threads. So far with spring-boot 3.2.0 I can build native executables or take advantage of virtual threads, but not both:

env:

uname -a
Linux kl-ubuntu 6.2.0-35-generic #35~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Oct  6 10:23:26 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

java -version
java version "21" 2023-09-19
Java(TM) SE Runtime Environment Oracle GraalVM 21+35.1 (build 21+35-jvmci-23.1-b15)
Java HotSpot(TM) 64-Bit Server VM Oracle GraalVM 21+35.1 (build 21+35-jvmci-23.1-b15, mixed mode, sharing)

sample project:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.0</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>gvm_virtual_threads</artifactId>
    <version>0.0.1</version>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

the only class:

package com.example.demo;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class DemoApplication {
    private final static Logger logger = LoggerFactory.getLogger(DemoApplication.class);

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @GetMapping("/greeting")
    public String greet() {
        logger.info("Inside greeting");
        return "Hi!";
    }
}

compiling:

mvn clean -Pnative native:compile

executing jvm without virtual threads and consuming it

java -jar target/gvm_virtual_threads-0.0.1.jar &
curl localhost:8080/greeting

log:

2023-11-25T22:02:03.255-03:00  INFO 2580376 --- [nio-8080-exec-3] com.example.demo.DemoApplication          : Inside greeting

executing jvm with virtual threads and consuming it

java -jar target/gvm_virtual_threads-0.0.1.jar --spring.threads.virtual.enabled=true &
curl localhost:8080/greeting

log:

2023-11-25T22:05:28.564-03:00  INFO 2580516 --- [omcat-handler-0] com.example.demo.DemoApplication          : Inside greeting

I can see that the thread name changed from nio-8080-exec-3 to omcat-handler-0

But with graalvm native compilation both

./target/gvm_virtual_threads &
curl localhost:8080/greeting

and

./target/gvm_virtual_threads --spring.threads.virtual.enabled=true &
curl localhost:8080/greeting

logs the same thread name:

2023-11-25T22:09:05.675-03:00  INFO 2580647 --- [nio-8080-exec-3] com.example.demo.DemoApplication          : Inside greeting

I know this isn't the best way to corroborate if virtual threads is on, but when stressing the app and querying micrometer metrics via actuator I can see no reduction in jvm_threads_peak_threads on graalvm compilations, when in jvm compilations there is.

Is this not an intended use case? Am I doing something wrong?

Answer 1

Setting spring.threads.virtual.enabled=true changes the beans that are in the application context. The closed-world assumptions of GraalVM and AOT processing do not allow the beans that are in the application context to be modified at runtime.

To use virtual threads in a native image, set spring.threads.virtual.enabled=true in your application.properties file and then build the image.