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.*;
  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
   *
   * Created by xuxueli on 17/3/10.
   */
  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);
  	}
  
  }
  