opentelemetry-spring-webflux-5.3 lack context inside controller

[KayWu]

Describe the bug

@RestController
public class TestController {

    @GetMapping("/test")
    public String traceId() {
        // returns invalid trace id: 00000000000000000000000000000000
        return Span.current().getSpanContext().getTraceId();
    }

    @GetMapping("/mono")
    public Mono<String> traceIdUsingMono() {
        return Mono.defer(()-> Mono.just(Span.current().getSpanContext().getTraceId()));
    }
}

@Configuration
public class OpentelemetryConfig {

    @Bean
    public OpenTelemetry openTelemetry() {
        Resource resource = Resource.getDefault().toBuilder().put(ResourceAttributes.SERVICE_NAME, "dice-server").put(ResourceAttributes.SERVICE_VERSION, "0.1.0").build();

        SdkTracerProvider sdkTracerProvider = SdkTracerProvider.builder()
                .addSpanProcessor(SimpleSpanProcessor.create(LoggingSpanExporter.create()))
                .setResource(resource)
                .build();

        return OpenTelemetrySdk.builder()
                .setTracerProvider(sdkTracerProvider)
                .setPropagators(ContextPropagators.create(TextMapPropagator.composite(W3CTraceContextPropagator.getInstance(), W3CBaggagePropagator.getInstance())))
                .buildAndRegisterGlobal();
    }

    @Bean
    public WebFilter webFilter(OpenTelemetry openTelemetry) {
        return SpringWebfluxTelemetry.builder(openTelemetry).build().createWebFilterAndRegisterReactorHook();
    }
}

<?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>3.2.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>opentelemtry-sample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>opentelemtry-sample</name>
    <description>Demo project for opentelemtry</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-api</artifactId>
        </dependency>

        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-sdk</artifactId>
        </dependency>
        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-exporter-logging</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>
        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-semconv</artifactId>
            <version>1.30.1-alpha</version>
        </dependency>
        <dependency>
            <groupId>io.opentelemetry.instrumentation</groupId>
            <artifactId>opentelemetry-spring-webflux-5.3</artifactId>
            <version>1.32.0-alpha</version>
        </dependency>
    </dependencies>


    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>io.opentelemetry</groupId>
                <artifactId>opentelemetry-bom</artifactId>
                <version>1.32.0</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

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

</project>

Code inside "/test" api doesn't have a valid context.

Steps to reproduce

Run Spring Boot Application.

curl localhost:8080/test
curl localhost:8080/mono

Expected behavior

/test and /mono should both return valid trace id.

This is the case for opentelemetry-spring-webflux-5.3 1.26.0-alpha.

Actual behavior

After upgrading to opentelemetry-spring-webflux-5.3 1.32.0-alpha alone with Spring Boot 3.2.1, /test returns 00000000000000000000000000000000, which is invalid trace id. '/mono' returns '2f34a6f4cdee5a8d10fdd5603fff342d', which is valid trace id.

Javaagent or library instrumentation version

opentelemetry-spring-webflux-5.3 v1.32.0-alpha

Environment

JDK: Temurin-17.0.5+8
OS: macOS 13.6.3

Additional context

No response