Adding the traceId from Spring Cloud Sleuth to response

Question

I am currently implementing Spring Cloud Sleuth in our project. I have a requirement to add the traceId to the response headers. Is there a way that this can be achieved?

Thanks,
Anoop

Answer 1

In Spring Sleuth 3.0.x, here is an example from the official doc.

@Component
@Order(TraceWebServletAutoConfiguration.TRACING_FILTER_ORDER + 1)
class MyFilter extends GenericFilterBean {

    private final Tracer tracer;

    MyFilter(Tracer tracer) {
        this.tracer = tracer;
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        Span currentSpan = this.tracer.currentSpan();
        if (currentSpan == null) {
            chain.doFilter(request, response);
            return;
        }
        // for readability we're returning trace id in a hex form
        ((HttpServletResponse) response).addHeader("ZIPKIN-TRACE-ID",
                currentSpan.context().traceIdString());
        // we can also add some custom tags
        currentSpan.tag("custom", "tag");
        chain.doFilter(request, response);
    }

}

Answer 2

If you're using jersey One approach is to add jersey response filter and use Trace (autowired) from spring sleuth org.springframework.cloud.sleuth.Tracer

public class TraceHeaderInterceptor implements ContainerResponseFilter {

    @Override
    public void filter(ContainerRequestContext requestContext, ContainerResponseContext responseContext) throws IOException {
        val responseHeaders = responseContext.getHeaders();
        if (!responseHeaders.containsKey(TRACE_ID_HEADER_NAME)) {
            val traceId = tracer.getCurrentSpan().context().traceIdString();
            responseHeaders.add(TRACE_ID_HEADER_NAME, traceId);
        }
    }

    private static final String TRACE_ID_HEADER_NAME = "X-B3-Traceid";
    private final Tracer tracer;

    public TraceHeaderInterceptor(Tracer tracer) {
        this.tracer = tracer;
    }
}

We added this to our API gateway to avoid having to change each and every microservice