zipkin.scala

// service A
val tracer = ZipkinTracer.mk(host = "localhost", port = 9410, sampleRate = 1)

Trace.unwind {
  Trace.pushTracerAndSetNextId(tracer)
  Trace.recordRpcname("service-A", "GET")
  Trace.record(Annotation.ServerRecv())

  // client call to service B (see below)
  
  Trace.record(Annotation.ServerSend())
}

// service A - client call to service B
Trace.unwind {
  Trace.setId(Trace.nextId)
  Trace.recordRpcname("service-B", "GET")

  // set http headers    
  
  Trace.record(Annotation.ClientSend())  
  // make http call
  Trace.record(Annotation.ClientRecv())
}

// service B
val tracer = ZipkinTracer.mk(host = "localhost", port = 9410, sampleRate = 1)

Trace.unwind {
  Trace.pushTracer(tracer)

  // parse HTTP headers
  Trace.setId(TraceId(traceId, parentSpanId, sid, sampled, flags))

  Trace.recordRpcname("service-B", "GET")

  Trace.record(Annotation.ServerRecv())
  // Trace.record("received")
  // do some work
  // Trace.record("sent")
  Trace.record(Annotation.ServerSend())
}