1、基本概念
2、信号量类
3、测试类
4、测试日志
基本概念
计数信号量是一种锁，它可以让用户限制一项资源最多能够同时被多少个进程访问，
技术信号量和其他锁的区别：当客户端获取锁失败时，客户端会选择等待；而获取信号量失败时，通常直接退出，并向用户提示“资源繁忙”，由用户决定下一步如何处理。
信号量类
import java.util.UUID; import redis.clients.jedis.Jedis; import redis.clients.jedis.Pipeline; import redis.clients.jedis.Response; public class Semaphore_Lock { public static String acquire_semaphore(Jedis redis,String sem_name,int limit,long timeout){ String identifier=UUID.randomUUID().toString(); long now=System.currentTimeMillis(); Pipeline pipeline=redis.pipelined(); //清理其他持有者过期信号量 pipeline.zremrangeByScore(sem_name, 0, now-timeout); pipeline.zadd(sem_name,now,identifier); Responserank=pipeline.zrank(sem_name, identifier); pipeline.syncAndReturnAll(); if((Long)rank.get()<limit){ System.out.println(Thread.currentThread().getName()+" identifier rank :"+rank.get()); return identifier; }else{ System.out.println(Thread.currentThread().getName()+" identifier rank :"+rank.get()+",too late"); } redis.zrem(sem_name, identifier); return null; } public static Long release_semaphore(Jedis redis,String sem_name,String identifier){ return redis.zrem(sem_name, identifier); } }
测试类
import redis.clients.jedis.Jedis; public class TestSemaphore_Lock { public static void main(String[] args) { System.out.println( " main start"); for (int i = 0; i < 1000; i++) { Test_Thread_lock threadA = new Test_Thread_lock(); threadA.start(); try { // Thread.sleep(1); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } class Test_Thread_lock extends Thread { public void run() { System.out.println(Thread.currentThread().getName() + " 启动运行"); Jedis redis=JedisUtil.getJedis(); while(true){ if(redis==null){ redis=JedisUtil.getJedis(); System.out.println(Thread.currentThread().getName() + " 获取redis连接失败，等待几秒后，继续尝试获取.conn conn conn"); try { sleep(100); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } continue; } String indentifier = Semaphore_Lock.acquire_semaphore(redis, "sem_name", 20, 1000*60); if (indentifier == null) { System.out.println(Thread.currentThread().getName() + " 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore"); }else{ System.out.println(Thread.currentThread().getName() + " 执行任务"); try { sleep(10); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } Semaphore_Lock.release_semaphore(redis,"sem_name", indentifier); redis.close(); break; } } } }
测试日志
Thread-274 identifier rank :22,too late Thread-255 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-213 identifier rank :23,too late Thread-255 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-213 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-255 identifier rank :22,too late Thread-213 identifier rank :21,too late Thread-274 identifier rank :21,too late Thread-255 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-213 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-255 identifier rank :21,too late Thread-213 identifier rank :21,too late Thread-274 identifier rank :21,too late Thread-255 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-213 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-255 identifier rank :20,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-213 identifier rank :21,too late Thread-255 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-255 identifier rank :20,too late Thread-213 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-255 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-213 identifier rank :19 Thread-213 执行任务 Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-255 identifier rank :19 Thread-255 执行任务 Thread-274 identifier rank :20,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :20,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :21,too late Thread-274 获取信号量失败，取消任务. Semaphore Semaphore Semaphore Semaphore Thread-274 identifier rank :18 Thread-274 执行任务 Thread-963 identifier rank :16 Thread-963 执行任务