TraceId in Spring Boot 3 is not propagated

I try to propagate the trace Id between micro service calls. It does not seem the RestTemplate propagates the traceId, even though I am using RestTemplateBuilder and have actuator and a tracing bridge in the classpath.

I am running on Spring Boot 3.3.3 and Java 17. here the pom.xml:

<?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>3.3.3</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.test</groupId><artifactId>tracepropagation</artifactId><version>0.0.1-SNAPSHOT</version><name>tracepropagation</name><properties><java.version>17</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>io.micrometer</groupId><artifactId>micrometer-tracing-bridge-otel</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId><configuration><excludes><exclude><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></exclude></excludes></configuration></plugin></plugins></build></project>

This is my RestTemplate config

@Configuration@EnableConfigurationProperties(AppProperties.class)public class AppConfig {    @Bean    public RestTemplate restTemplate(RestTemplateBuilder builder) {        return builder.build();    }}

I test with a simple request forward to the same service using the rest template:

@RestController@AllArgsConstructor@Slf4jpublic class AppController {    private final RestTemplate restTemplate;    private final AppProperties props;    @GetMapping(path = "/forward")    public String forward() {        log.info("forward endpoint entered");        return this.restTemplate.getForObject("http://localhost:" + props.getPort() +"/hello", String.class);    }    @GetMapping(path = "/hello")    public String hello(){        log.info("hello endpoint entered");        return "hello";    }}

I wrote a test case, which expects the same trace Id in the log from the /forward endpoint and the log in the /hello endpoint:

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)class TracepropagationApplicationTests {    @LocalServerPort    private int port;    @Autowired    private AppProperties props;    @Autowired    private TestRestTemplate restTemplate;    @Captor    ArgumentCaptor<ILoggingEvent> logCaptor;    @Mock    private Appender<ILoggingEvent> mockAppender;    @BeforeEach    void beforeEach(){        final Logger root = (Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);        when(this.mockAppender.getName()).thenReturn("MOCK");        root.addAppender(this.mockAppender);        root.setLevel(Level.INFO);        doNothing().when(mockAppender).doAppend(logCaptor.capture());    }    @Test    void testTraceIdPropagation() {        props.setPort(port);        assertThat(restTemplate.getForObject("http://localhost:" + port +"/forward", String.class)).isEqualTo("hello");        String firstLogTraceId = this.getLogTraceId("forward endpoint entered");        String secondLogTraceId = this.getLogTraceId("hello endpoint entered");        assertThat(firstLogTraceId).isEqualTo(secondLogTraceId);    }    private String getLogTraceId(String logMessage) {        var traceOptional = logCaptor.getAllValues().stream().filter(e -> e.getFormattedMessage().contains(logMessage))                .findAny()                .map(ILoggingEvent::getMDCPropertyMap)                .map(m -> m.get("traceId"));        assertThat(traceOptional).isPresent();        return traceOptional.get();    }}

However, this test case fails. From what I read in the documentation, the auto configuration should work, if I use the RestTemplateBuilder autowired from Spring Boot.

It does not seem to propagate the trace Id though.

thx in advance!

Here also the AppProperties class just to be complete:

@ConfigurationProperties(prefix = "com.test")@Datapublic class AppProperties {    private int port;}