content: package com.xxl.job.admin.core.route.strategy;
  
  import com.xxl.job.admin.core.route.ExecutorRouter;
  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.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
   *
   * Created by xuxueli on 17/3/10.
   */
  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);
  	}
  
  }
  