code: func (pool *serverPool) saveNodes() {
  	list := make([]*poolEntry, len(pool.knownQueue.queue))
  	for i := range list {
  		list[i] = pool.knownQueue.fetchOldest()
  	}
  	enc, err := rlp.EncodeToBytes(list)
  	if err == nil {
  		pool.db.Put(pool.dbKey, enc)
  	}
  }
docs: // saveNodes saves known nodes and their statistics into the database. Nodes are
  // ordered from least to most recently connected.