code: func (s *Server) indexGet(ctx *middleware.Context, req models.IndexGet) {
  
  	// query nodes don't own any data.
  	if s.MetricIndex == nil {
  		response.Write(ctx, response.NewMsgp(404, nil))
  		return
  	}
  
  	def, ok := s.MetricIndex.Get(req.MKey)
  	if !ok {
  		response.Write(ctx, response.NewError(http.StatusNotFound, "Not Found"))
  		return
  	}
  
  	response.Write(ctx, response.NewMsgp(200, &def))
  }
docs: // IndexGet returns a msgp encoded schema.MetricDefinition