code: func (r *Router) findDirectRoute(datacenter string) (*Manager, *metadata.Server, bool) {
  	r.RLock()
  	defer r.RUnlock()
  
  	// Get the list of managers for this datacenter. This will usually just
  	// have one entry, but it's possible to have a user-defined area + WAN.
  	managers, ok := r.managers[datacenter]
  	if !ok {
  		return nil, nil, false
  	}
  
  	// Try each manager until we get a server.
  	for _, manager := range managers {
  		if manager.IsOffline() {
  			continue
  		}
  
  		if s := manager.FindServer(); s != nil {
  			return manager, s, true
  		}
  	}
  
  	// Didn't find a route (even via an unhealthy server).
  	return nil, nil, false
  }
docs: // findDirectRoute looks for a route to the given datacenter if it's directly
  // adjacent to the server.