content: package com.platform.admin.core.route.strategy;
  
  import com.platform.core.biz.model.ReturnT;
  import com.platform.core.biz.model.TriggerParam;
  import com.platform.admin.core.route.ExecutorRouter;
  
  import java.util.*;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  /**
   * 单个JOB对应的每个执行器，使用频率最低的优先被选举
   *      a(*)、LFU(Least Frequently Used)：最不经常使用，频率/次数
   *      b、LRU(Least Recently Used)：最近最久未使用，时间
   *
   */
  public class ExecutorRouteLFU extends ExecutorRouter {
  
      private static ConcurrentMap<Integer, HashMap<String, Integer>> jobLfuMap = new ConcurrentHashMap<Integer, HashMap<String, Integer>>();
      private static long CACHE_VALID_TIME = 0;
  
      public String route(int jobId, List<String> addressList) {
  
          // cache clear
          if (System.currentTimeMillis() > CACHE_VALID_TIME) {
              jobLfuMap.clear();
              CACHE_VALID_TIME = System.currentTimeMillis() + 1000*60*60*24;
          }
  
          // lfu item init
          HashMap<String, Integer> lfuItemMap = jobLfuMap.get(jobId);     // Key排序可以用TreeMap+构造入参Compare；Value排序暂时只能通过ArrayList；
          if (lfuItemMap == null) {
              lfuItemMap = new HashMap<String, Integer>();
              jobLfuMap.putIfAbsent(jobId, lfuItemMap);   // 避免重复覆盖
          }
  
          // put new
          for (String address: addressList) {
              if (!lfuItemMap.containsKey(address) || lfuItemMap.get(address) >1000000 ) {
                  lfuItemMap.put(address, new Random().nextInt(addressList.size()));  // 初始化时主动Random一次，缓解首次压力
              }
          }
          // remove old
          List<String> delKeys = new ArrayList<>();
          for (String existKey: lfuItemMap.keySet()) {
              if (!addressList.contains(existKey)) {
                  delKeys.add(existKey);
              }
          }
          if (delKeys.size() > 0) {
              for (String delKey: delKeys) {
                  lfuItemMap.remove(delKey);
              }
          }
  
          // load least userd count address
          List<Map.Entry<String, Integer>> lfuItemList = new ArrayList<Map.Entry<String, Integer>>(lfuItemMap.entrySet());
          Collections.sort(lfuItemList, new Comparator<Map.Entry<String, Integer>>() {
              @Override
              public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
                  return o1.getValue().compareTo(o2.getValue());
              }
          });
  
          Map.Entry<String, Integer> addressItem = lfuItemList.get(0);
          String minAddress = addressItem.getKey();
          addressItem.setValue(addressItem.getValue() + 1);
  
          return addressItem.getKey();
      }
  
      @Override
      public ReturnT<String> route(TriggerParam triggerParam, List<String> addressList) {
          String address = route(triggerParam.getJobId(), addressList);
          return new ReturnT<String>(address);
      }
  
  }
  