This library provides instrumentation for Spring Web applications (Boot and MVC). It creates tracing data for server requests and also client requests (RestTemplate and AsyncRestTemplate).

This project provides instrumentation only for spring-web package. In other words it traces only HTTP requests made to Spring Boot/WEB app and outgoing requests using Spring RestTemplate. However it allows you to use OpenTracing API directly in your code and combine different OpenTracing instrumentations together easily (e.g. OpenFeign).

Whereas spring-cloud-sleuth combines instrumentations for different frameworks together. It is not currently possible to use the OpenTracing API, or wire different instrumentations that are not supported by sleuth (it might be inconvenient).

Server span is started in Web Servlet Filter, then tracing interceptor adds spring related tags and logs. There are use case when spring boot invokes a handler after a request processing in filter finished, in this case interceptor starts a new span as followsFrom which references the initial span created in the servlet filter.

If you are using Spring Boot the easiest way how to configure OpenTracing instrumentation is to use auto-configuration:

<dependency>
  <groupId>io.opentracing.contrib</groupId>
  <artifactId>opentracing-spring-web-autoconfigure</artifactId>
</dependency>

Just provide an OpenTracing tracer bean and all required configuration is automatically done for you. It also instruments all RestTemplate and AsyncRestTemplate beans.

Configuration needs to add TracingFilter and TracingHandlerInterceptor. Both of these classes are required!

Tracing interceptor can be instantiated manually or injected via CDI, but it needs bean of type Tracer configured.

Java based configuration:

@Configuration
@Import({TracingHandlerInterceptor.class})
public class MVCConfiguration extends WebMvcConfigurerAdapter {

    @Autowired
    private Tracer tracer;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new TracingHandlerInterceptor(tracer));
    }

    @Bean
    public FilterRegistrationBean tracingFilter() {
        TracingFilter tracingFilter = new TracingFilter(tracer);

        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(tracingFilter);
        filterRegistrationBean.addUrlPatterns("/*");
        filterRegistrationBean.setOrder(Integer.MIN_VALUE);
        filterRegistrationBean.setAsyncSupported(true);

        return filterRegistrationBean;
    }
}

XML based configuration can be used too. Filter can be also directly defined in web.xml.

RestTemplate restTemplate = new RestTemplate();
restTemplate.setInterceptors(Collections.singletonList(new TracingRestTemplateInterceptor(tracer)));

// the same applies for AsyncRestTemplate 

@RequestMapping("/hello")
public String hello(HttpServletRequest request) {
    ActiveSpan serverSpan = tracer.activeSpan();

    ActiveSpan span = tracer.buildSpan("localSpan");
            .asChildOf(serverSpan.context())
            .start();
    span.deactivate();
    
    return "Hello world!";
}

./mvnw clean install

Follow instructions in RELEASE