Redis实现分布式锁的几种方法总结

Redis实现分布式锁
*
* 在集群等多服务器中经常使用到同步处理一下业务，这是普通的事务是满足不了业务需求，需要分布式锁
*
* 分布式锁的常用3种实现：
*        0.数据库乐观锁实现
*        1.Redis实现  --- 使用redis的setnx()、get()、getset()方法，用于分布式锁，解决死锁问题
*        2.Zookeeper实现
*           参考：http://surlymo.iteye.com/blog/2082684
*              https://www.jb51.net/article/103617.htm
*              http://www.hollischuang.com/archives/1716"htmlcode">

package com.jay.service.redis; 
 
/** 
 * Redis分布式锁接口 
 * Created by hetiewei on 2017/4/7. 
 */ 
public interface RedisDistributionLock { 
  /** 
   * 加锁成功，返回加锁时间 
   * @param lockKey 
   * @param threadName 
   * @return 
   */ 
  public long lock(String lockKey, String threadName); 
 
  /** 
   * 解锁， 需要更新加锁时间，判断是否有权限 
   * @param lockKey 
   * @param lockValue 
   * @param threadName 
   */ 
  public void unlock(String lockKey, long lockValue, String threadName); 
 
  /** 
   * 多服务器集群，使用下面的方法，代替System.currentTimeMillis()，获取redis时间，避免多服务的时间不一致问题！！！ 
   * @return 
   */ 
  public long currtTimeForRedis(); 
} 



   2.定义锁实现




package com.jay.service.redis.impl; 
 
import com.jay.service.redis.RedisDistributionLock; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import org.springframework.dao.DataAccessException; 
import org.springframework.data.redis.connection.RedisConnection; 
import org.springframework.data.redis.core.RedisCallback; 
import org.springframework.data.redis.core.StringRedisTemplate; 
import org.springframework.data.redis.serializer.RedisSerializer; 
 
import java.util.concurrent.TimeUnit; 
 
/** 
 * Created by hetiewei on 2017/4/7. 
 */ 
public class RedisLockImpl implements RedisDistributionLock { 
 
  //加锁超时时间，单位毫秒， 即：加锁时间内执行完操作，如果未完成会有并发现象 
  private static final long LOCK_TIMEOUT = 5*1000; 
 
  private static final Logger LOG = LoggerFactory.getLogger(RedisLockImpl.class); 
 
  private StringRedisTemplate redisTemplate; 
 
  public RedisLockImpl(StringRedisTemplate redisTemplate) { 
    this.redisTemplate = redisTemplate; 
  } 
 
  /** 
   * 加锁 
   * 取到锁加锁，取不到锁一直等待知道获得锁 
   * @param lockKey 
   * @param threadName 
   * @return 
   */ 
  @Override 
  public synchronized long lock(String lockKey, String threadName) { 
    LOG.info(threadName+"开始执行加锁"); 
    while (true){ //循环获取锁 
      //锁时间 
      Long lock_timeout = currtTimeForRedis()+ LOCK_TIMEOUT +1; 
      if (redisTemplate.execute(new RedisCallback<Boolean>() { 
        @Override 
        public Boolean doInRedis(RedisConnection redisConnection) throws DataAccessException { 
          //定义序列化方式 
          RedisSerializer<String> serializer = redisTemplate.getStringSerializer(); 
          byte[] value = serializer.serialize(lock_timeout.toString()); 
          boolean flag = redisConnection.setNX(lockKey.getBytes(), value); 
          return flag; 
        } 
      })){ 
        //如果加锁成功 
        LOG.info(threadName +"加锁成功 ++++ 111111"); 
        //设置超时时间，释放内存 
        redisTemplate.expire(lockKey, LOCK_TIMEOUT, TimeUnit.MILLISECONDS); 
        return lock_timeout; 
      }else { 
        //获取redis里面的时间 
        String result = redisTemplate.opsForValue().get(lockKey); 
        Long currt_lock_timeout_str = result==null"加锁成功 ++++ 22222"); 
            //设置超时间，释放内存 
            redisTemplate.expire(lockKey, LOCK_TIMEOUT, TimeUnit.MILLISECONDS); 
 
            //返回加锁时间 
            return lock_timeout; 
          } 
        } 
      } 
 
      try { 
        LOG.info(threadName +"等待加锁， 睡眠100毫秒"); 
//        TimeUnit.MILLISECONDS.sleep(100); 
        TimeUnit.MILLISECONDS.sleep(200); 
      } catch (InterruptedException e) { 
        e.printStackTrace(); 
      } 
    } 
  } 
 
  /** 
   * 解锁 
   * @param lockKey 
   * @param lockValue 
   * @param threadName 
   */ 
  @Override 
  public synchronized void unlock(String lockKey, long lockValue, String threadName) { 
    LOG.info(threadName + "执行解锁==========");//正常直接删除 如果异常关闭判断加锁会判断过期时间 
    //获取redis中设置的时间 
    String result = redisTemplate.opsForValue().get(lockKey); 
    Long currt_lock_timeout_str = result ==null"解锁成功------------------"); 
    } 
  } 
 
  /** 
   * 多服务器集群，使用下面的方法，代替System.currentTimeMillis()，获取redis时间，避免多服务的时间不一致问题！！！ 
   * @return 
   */ 
  @Override 
  public long currtTimeForRedis(){ 
    return redisTemplate.execute(new RedisCallback<Long>() { 
      @Override 
      public Long doInRedis(RedisConnection redisConnection) throws DataAccessException { 
        return redisConnection.time(); 
      } 
    }); 
  } 
 
} 



  3.分布式锁验证      




@RestController 
@RequestMapping("/distribution/redis") 
public class RedisLockController { 
 
  private static final String LOCK_NO = "redis_distribution_lock_no_"; 
 
  private static int i = 0; 
 
  private ExecutorService service; 
 
  @Autowired 
  private StringRedisTemplate redisTemplate; 
 
  /** 
   * 模拟1000个线程同时执行业务，修改资源 
   * 
   * 使用线程池定义了20个线程 
   * 
   */ 
  @GetMapping("lock1") 
  public void testRedisDistributionLock1(){ 
 
    service = Executors.newFixedThreadPool(20); 
 
    for (int i=0;i<1000;i++){ 
      service.execute(new Runnable() { 
        @Override 
        public void run() { 
          task(Thread.currentThread().getName()); 
        } 
      }); 
    } 
 
  } 
 
  @GetMapping("/{key}") 
  public String getValue(@PathVariable("key") String key){ 
    Serializable result = redisTemplate.opsForValue().get(key); 
    return result.toString(); 
  } 
 
  private void task(String name) { 
//    System.out.println(name + "任务执行中"+(i++)); 
 
    //创建一个redis分布式锁 
    RedisLockImpl redisLock = new RedisLockImpl(redisTemplate); 
    //加锁时间 
    Long lockTime; 
    if ((lockTime = redisLock.lock((LOCK_NO+1)+"", name))!=null){ 
      //开始执行任务 
      System.out.println(name + "任务执行中"+(i++)); 
      //任务执行完毕 关闭锁 
      redisLock.unlock((LOCK_NO+1)+"", lockTime, name); 
    } 
 
  } 
} 



4.结果验证：


      在Controller中模拟了1000个线程，通过线程池方式提交，每次20个线程抢占分布式锁，抢到分布式锁的执行代码，没抢到的等待


     结果如下：




2017-04-07 16:27:17.385 INFO 8652 --- [pool-2-thread-4] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-4等待加锁， 睡眠100毫秒
2017-04-07 16:27:17.385 INFO 8652 --- [pool-2-thread-7] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-7解锁成功------------------
    2017-04-07 16:27:17.391 INFO 8652 --- [pool-2-thread-5] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-5加锁成功 ++++ 111111
pool-2-thread-5任务执行中994
2017-04-07 16:27:17.391 INFO 8652 --- [pool-2-thread-5] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-5执行解锁==========
    2017-04-07 16:27:17.391 INFO 8652 --- [pool-2-thread-1] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-1等待加锁， 睡眠100毫秒
2017-04-07 16:27:17.391 INFO 8652 --- [pool-2-thread-5] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-5解锁成功------------------
    2017-04-07 16:27:17.397 INFO 8652 --- [pool-2-thread-6] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-6加锁成功 ++++ 111111
pool-2-thread-6任务执行中995
2017-04-07 16:27:17.398 INFO 8652 --- [pool-2-thread-6] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-6执行解锁==========
    2017-04-07 16:27:17.398 INFO 8652 --- [pool-2-thread-6] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-6解锁成功------------------
    2017-04-07 16:27:17.400 INFO 8652 --- [ool-2-thread-19] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-19加锁成功 ++++ 111111
pool-2-thread-19任务执行中996
2017-04-07 16:27:17.400 INFO 8652 --- [ool-2-thread-19] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-19执行解锁==========
    2017-04-07 16:27:17.400 INFO 8652 --- [ool-2-thread-19] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-19解锁成功------------------
    2017-04-07 16:27:17.571 INFO 8652 --- [ool-2-thread-11] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-11加锁成功 ++++ 111111
pool-2-thread-11任务执行中997
2017-04-07 16:27:17.572 INFO 8652 --- [ool-2-thread-11] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-11执行解锁==========
    2017-04-07 16:27:17.572 INFO 8652 --- [ool-2-thread-11] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-11解锁成功------------------
    2017-04-07 16:27:17.585 INFO 8652 --- [pool-2-thread-4] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-4加锁成功 ++++ 111111
pool-2-thread-4任务执行中998
2017-04-07 16:27:17.586 INFO 8652 --- [pool-2-thread-4] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-4执行解锁==========
    2017-04-07 16:27:17.586 INFO 8652 --- [pool-2-thread-4] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-4解锁成功------------------
    2017-04-07 16:27:17.591 INFO 8652 --- [pool-2-thread-1] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-1加锁成功 ++++ 111111
pool-2-thread-1任务执行中999
2017-04-07 16:27:17.591 INFO 8652 --- [pool-2-thread-1] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-1执行解锁==========
    2017-04-07 16:27:17.591 INFO 8652 --- [pool-2-thread-1] c.jay.service.redis.impl.RedisLockImpl  : pool-2-thread-1解锁成功------------------




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