Jedis分佈式鎖實現

 redis分佈式鎖解決多個應用進程間同步操做

整理了不少網上文檔 發現都沒有解決以下問題。。。

參考

http://www.cnblogs.com/it-cen/p/4984272.html

...

1.時間同步問題

2.在一個進程cash後失效時間後自動釋放鎖

3.有些多線程race condition沒有考慮到

 

如下java版本實現完全解決  充分測試   

 

import java.util.List;
import java.util.UUID;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.Transaction;
import redis.clients.jedis.exceptions.JedisException;

/**
 * Jedis實現分佈式鎖
 * 
 * @author 三文魚
 *
 */
public class DistributionLock {
    private final JedisPool jedisPool;

    public DistributionLock(JedisPool jedisPool) {
        this.jedisPool = jedisPool;
    }

    /**
     * 獲取分佈式鎖
     * 
     * @param lockName
     *            競爭獲取鎖key
     * @param acquireTimeoutInMS
     *            獲取鎖超時時間
     * @param lockTimeoutInMS
     *            鎖的超時時間
     * @return 獲取鎖標識
     */
    public String acquireLockWithTimeout(String lockName,
            long acquireTimeoutInMS, long lockTimeoutInMS) {
        Jedis conn = null;
        boolean broken = false;
        String retIdentifier = null;
        try {
            conn = jedisPool.getResource();
            String identifier = UUID.randomUUID().toString();
            String lockKey = "lock:" + lockName;
            int lockExpire = (int) (lockTimeoutInMS / 1000);

            long end = System.currentTimeMillis() + acquireTimeoutInMS;
            while (System.currentTimeMillis() < end) {
                if (conn.setnx(lockKey, identifier) == 1) {
                    conn.expire(lockKey, lockExpire);
                    retIdentifier = identifier;
                }
                if (conn.ttl(lockKey) == -1) {
                    conn.expire(lockKey, lockExpire);
                }

                try {
                    Thread.sleep(10);
                } catch (InterruptedException ie) {
                    Thread.currentThread().interrupt();
                }
            }
        } catch (JedisException je) {
            if (conn != null) {
                broken = true;
                jedisPool.returnBrokenResource(conn);
            }
        } finally {
            if (conn != null && !broken) {
                jedisPool.returnResource(conn);
            }
        }
        return retIdentifier;
    }

    /**
     * 釋放鎖
     * @param lockName 競爭獲取鎖key
     * @param identifier 釋放鎖標識
     * @return
     */
    public boolean releaseLock(String lockName, String identifier) {
        Jedis conn = null;
        boolean broken = false;
        String lockKey = "lock:" + lockName;
        boolean retFlag = false;
        try {
            conn = jedisPool.getResource();
            while (true) {
                conn.watch(lockKey);
                if (identifier.equals(conn.get(lockKey))) {
                    Transaction trans = conn.multi();
                    trans.del(lockKey);
                    List<Object> results = trans.exec();
                    if (results == null) {
                        continue;
                    }
                    retFlag = true;
                }
                conn.unwatch();
                break;
            }

        } catch (JedisException je) {
            if (conn != null) {
                broken = true;
                jedisPool.returnBrokenResource(conn);
            }
        } finally {
            if (conn != null && !broken) {
                jedisPool.returnResource(conn);
            }
        }
        return retFlag;
    }

}