title: WebClient instrumentation in spring sleuth
body: <p>I'm wondering whether sleuth has reactive WebClient instrumentation supported.</p>
  
  <p>I did't find it from the document:</p>
  
  <p><em>Instruments common ingress and egress points from Spring applications (servlet filter, async endpoints, rest template, scheduled actions, message channels, Zuul filters, and Feign client).</em></p>
  
  <p>My case:</p>
  
  <p>I may use WebClient in either a WebFilter or my rest resource to produce Mono.</p>
  
  <p>And I want:</p>
  
  <ul>
  <li>A sub span auto created as child of root span</li>
  <li>trace info propagated via headers</li>
  </ul>
  
  <p>If the instrumentation is not supported at the moment, Am I supposed to manually get the span from context and do it by myself like this:</p>
  
  <p><a href="https://stackoverflow.com/questions/50600040/opentracing-instrumentation-on-reactive-webclient">OpenTracing instrumentation on reactive WebClient</a></p>
  
  <p>Thanks</p>
  
  <p>Leon</p>