openzipkin/zipkin

@adriancole yes in our context a session means all calls made by the UI from the moment a user opens the UI until it is closed (think of it as login and logout). There is a specific HTTP header specifying a unique session Id (e.g.x-session-id), however not sure how to get access to this header from Zipkin JS.

Right now based on @basvanbeek suggestion I managed to set a new tag to the same value of the span Id so I can then be able to search on it (and it works). Below how I did it:

function newRecorder() {
  const logger = {
    logSpan: (span: any) => {
      //we add custom sessionId tag only if it's the first span
      if(!span.parentId){
        span.tags.sessionId = span.id;
      }
      httpLogger.logSpan(span);
    }
  };
  return new BatchRecorder({logger});
}

then when creating the tracer constant I just reference the newRecorder()function:

export const tracer = new Tracer({
  ctxImpl, 
  recorder: newRecorder(), 
  sampler: new sampler.CountingSampler(zipkinSamplingRate),
  localServiceName
});

if I can find a way to access to the http headers of a the HTTP call being traced, then I could just set span.tags.sessionId to the value of x-session-id.