code: func (s *HTTPServer) parseSource(req *http.Request, source *structs.QuerySource) {
  	s.parseDC(req, &source.Datacenter)
  	source.Ip = sourceAddrFromRequest(req)
  	if node := req.URL.Query().Get("near"); node != "" {
  		if node == "_agent" {
  			source.Node = s.agent.config.NodeName
  		} else {
  			source.Node = node
  		}
  	}
  }
docs: // parseSource is used to parse the ?near=<node> query parameter, used for
  // sorting by RTT based on a source node. We set the source's DC to the target
  // DC in the request, if given, or else the agent's DC.