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.ArrayList;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  /**
   * 单个JOB对应的每个执行器，最久为使用的优先被选举
   *      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 ExecutorRouteLRU extends ExecutorRouter {
  
      private static ConcurrentMap<Integer, LinkedHashMap<String, String>> jobLRUMap = new ConcurrentHashMap<Integer, LinkedHashMap<String, String>>();
      private static long CACHE_VALID_TIME = 0;
  
      public String route(int jobId, List<String> addressList) {
  
          // cache clear
          if (System.currentTimeMillis() > CACHE_VALID_TIME) {
              jobLRUMap.clear();
              CACHE_VALID_TIME = System.currentTimeMillis() + 1000*60*60*24;
          }
  
          // init lru
          LinkedHashMap<String, String> lruItem = jobLRUMap.get(jobId);
          if (lruItem == null) {
              /**
               * LinkedHashMap
               *      a、accessOrder：true=访问顺序排序（get/put时排序）；false=插入顺序排期；
               *      b、removeEldestEntry：新增元素时将会调用，返回true时会删除最老元素；可封装LinkedHashMap并重写该方法，比如定义最大容量，超出是返回true即可实现固定长度的LRU算法；
               */
              lruItem = new LinkedHashMap<String, String>(16, 0.75f, true);
              jobLRUMap.putIfAbsent(jobId, lruItem);
          }
  
          // put new
          for (String address: addressList) {
              if (!lruItem.containsKey(address)) {
                  lruItem.put(address, address);
              }
          }
          // remove old
          List<String> delKeys = new ArrayList<>();
          for (String existKey: lruItem.keySet()) {
              if (!addressList.contains(existKey)) {
                  delKeys.add(existKey);
              }
          }
          if (delKeys.size() > 0) {
              for (String delKey: delKeys) {
                  lruItem.remove(delKey);
              }
          }
  
          // load
          String eldestKey = lruItem.entrySet().iterator().next().getKey();
          String eldestValue = lruItem.get(eldestKey);
          return eldestValue;
      }
  
      @Override
      public ReturnT<String> route(TriggerParam triggerParam, List<String> addressList) {
          String address = route(triggerParam.getJobId(), addressList);
          return new ReturnT<String>(address);
      }
  
  }
  