content: package com.xxl.job.admin.core.route.strategy;
  
  import com.xxl.job.admin.core.route.ExecutorRouter;
  import com.xxl.job.admin.core.trigger.XxlJobTrigger;
  import com.xxl.job.core.biz.model.ReturnT;
  import com.xxl.job.core.biz.model.TriggerParam;
  
  import java.util.ArrayList;
  import java.util.LinkedHashMap;
  import java.util.concurrent.ConcurrentHashMap;
  
  /**
   * 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
   *
   * Created by xuxueli on 17/3/10.
   */
  public class ExecutorRouteLRU extends ExecutorRouter {
  
      private static ConcurrentHashMap<Integer, LinkedHashMap<String, String>> jobLRUMap = new ConcurrentHashMap<Integer, LinkedHashMap<String, String>>();
      private static long CACHE_VALID_TIME = 0;
  
      public String route(int jobId, ArrayList<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：ture=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<>(16, 0.75f, true);
              jobLRUMap.put(jobId, lruItem);
          }
  
          // put
          for (String address: addressList) {
              if (!lruItem.containsKey(address)) {
                  lruItem.put(address, address);
              }
          }
  
          // load
          String eldestKey = lruItem.entrySet().iterator().next().getKey();
          String eldestValue = lruItem.get(eldestKey);
          return eldestValue;
      }
  
  
      @Override
      public ReturnT<String> routeRun(TriggerParam triggerParam, ArrayList<String> addressList) {
  
          // address
          String address = route(triggerParam.getJobId(), addressList);
  
          // run executor
          ReturnT<String> runResult = XxlJobTrigger.runExecutor(triggerParam, address);
          runResult.setContent(address);
          return runResult;
      }
  
  }
  