Instead of servlet, this uses Spring Boot 1.5 to create a self-contained application that runs Spring WebMVC 4 controllers.
- brave.example.Frontend and Backend : Rest controllers with no tracing configuration
- brave.example.TracingConfiguration : This adds tracing by configuring the tracer, server and client tracing interceptors.
TracingConfiguration is automatically loaded due to META-INF/spring.factories
This allows the Frontend and Backend controllers to have no tracing
code. Inside the tracing configuration, you'll notice the rest template
is setup via a RestTemplateCustomizer, which ensures application-level
interceptors are not affected. Also, you'll notice layered tracing for
server requests. First, TracingFilter creates a span, then later,
SpanCustomizingAsyncHandlerInterceptor adds MVC tags to it.
Note This only lightly configures tracing. When doing anything serious, consider Spring Cloud Sleuth instead.