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redis-计数信号量

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12/02
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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);

        Response<Long> rank=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 = ; i < ; 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();

                } catch (InterruptedException e) {

                    // TODO Auto-generated catch block

                    e.printStackTrace();

                }

                continue;

            }

            String indentifier = Semaphore_Lock.acquire_semaphore(redis, "sem_name", , *);

            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();

                } 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-  identifier rank :,too late

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread-  identifier rank :,too late

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread-  identifier rank :,too late

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :

Thread-  执行任务

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :

Thread-  执行任务

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :,too late

Thread- 获取信号量失败，取消任务. Semaphore  Semaphore  Semaphore  Semaphore

Thread-  identifier rank :

Thread-  执行任务

Thread-  identifier rank :

Thread-  执行任务

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