# 主節(jié)點(diǎn)寫入鎖
SET resource_1 8a3e72 NX PX 10000  
OK

# 主節(jié)點(diǎn)宕機(jī)，從節(jié)點(diǎn)晉升但未同步鎖數(shù)據(jù)
# 新主節(jié)點(diǎn)處理客戶端B的請(qǐng)求
SET resource_1 5b9fd2 NX PX 10000  
OK  # 鎖被重復(fù)獲?。?

SET lock_key valueNX PX $ttl

if redis.call("get",KEYS[1]) == ARGV[1] then
   return redis.call("del",KEYS[1])
else
   return 0
end

// 偽代碼：獲取鎖后執(zhí)行業(yè)務(wù)邏輯
if (redLock.tryLock()) {
    // 觸發(fā)Full GC暫停300ms
    System.gc(); 
    
    // 此時(shí)鎖已過期，但客戶端仍在寫數(shù)據(jù)
    updateInventory(); 
}

package com.morris.redis.demo.redlock;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.params.SetParams;

import java.util.Collections;
import java.util.List;
import java.util.UUID;
import java.util.concurrent.TimeUnit;

/**
 * 使用jedis手寫RedLock
 */
public class JedisRedLock {

    public static final int EXPIRE_TIME = 30_000;

    private final List<JedisPool> jedisPoolList;

    private final String lockKey;

    private final String lockValue;

    public JedisRedLock(List<JedisPool> jedisPoolList, String lockKey) {
        this.jedisPoolList = jedisPoolList;
        this.lockKey = lockKey;
        this.lockValue = UUID.randomUUID().toString();
    }

    public void lock() {
        while (!tryLock()) {
            try {
                TimeUnit.MILLISECONDS.sleep(100); // 失敗后短暫等待
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        }
    }

    public boolean tryLock() {
        long startTime = System.currentTimeMillis();
        int successCount = 0;
        try {
            for (JedisPool jedisPool : jedisPoolList) {
                try (Jedis jedis = jedisPool.getResource();) {
                    // 原子化加鎖：SET lockKey UUID NX PX expireTime
                    String result = jedis.set(lockKey, lockValue,
                            SetParams.setParams().nx().px(EXPIRE_TIME));
                    if ("OK".equals(result)) {
                        successCount++;
                    }
                }
            }
            // 計(jì)算獲取鎖耗時(shí)
            long elapsedTime = System.currentTimeMillis() - startTime;

            // 驗(yàn)證：多數(shù)節(jié)點(diǎn)成功 且 耗時(shí)小于TTL
            return successCount >= (jedisPoolList.size() / 2 + 1) && elapsedTime < EXPIRE_TIME;
        } finally {
            // 若加鎖失敗，立即釋放已獲得的鎖
            if (successCount < (jedisPoolList.size() / 2 + 1)) {
                unlock();
            }
        }
    }

    public void unlock() {
        String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";

        for (JedisPool jedisPool : jedisPoolList) {
            try (Jedis jedis = jedisPool.getResource()) {
                jedis.eval(script, Collections.singletonList(lockKey), Collections.singletonList(lockValue));
            }
        }
    }

}

package com.morris.redis.demo.redlock;

import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * 手寫RedLock的使用
 */
public class JedisRedLockDemo {

    private volatile static int count;

    public static void main(String[] args) throws InterruptedException {
        List<JedisPool> jedisPoolList = new ArrayList<>();
        jedisPoolList.add(new JedisPool(new JedisPoolConfig(), "127.0.0.1", 6379));
        jedisPoolList.add(new JedisPool(new JedisPoolConfig(), "127.0.0.1", 6380));
        jedisPoolList.add(new JedisPool(new JedisPoolConfig(), "127.0.0.1", 6381));
        jedisPoolList.add(new JedisPool(new JedisPoolConfig(), "127.0.0.1", 6382));
        jedisPoolList.add(new JedisPool(new JedisPoolConfig(), "127.0.0.1", 6383));

        int threadCount = 3;
        CountDownLatch countDownLatch = new CountDownLatch(threadCount);
        ExecutorService executorService = Executors.newFixedThreadPool(threadCount);

        for (int i = 0; i < threadCount; i++) {
            executorService.submit(() -> {
                JedisRedLock jedisRedLock = new JedisRedLock(jedisPoolList, "lock-key");
                jedisRedLock.lock();
                try {
                    System.out.println(Thread.currentThread().getName() + "獲得鎖，開始執(zhí)行業(yè)務(wù)邏輯。。。");
                    try {
                        TimeUnit.SECONDS.sleep(3);
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                    System.out.println(Thread.currentThread().getName() + "獲得鎖，結(jié)束執(zhí)行業(yè)務(wù)邏輯。。。");
                    count++;
                } finally {
                    jedisRedLock.unlock();
                }
                countDownLatch.countDown();
            });
        }

        countDownLatch.await();
        executorService.shutdown();
        System.out.println(count);
    }

}

package com.morris.redis.demo.redlock;

import org.redisson.Redisson;
import org.redisson.RedissonRedLock;
import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;
import org.redisson.config.Config;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * Redisson中紅鎖的使用
 */
public class RedissonRedLockDemo {

    private volatile static int count;

    public static void main(String[] args) throws InterruptedException {

        List<String> serverList = Arrays.asList("redis://127.0.0.1:6379", "redis://127.0.0.1:6380", "redis://127.0.0.1:6381",
                "redis://127.0.0.1:6382", "redis://127.0.0.1:6383");

        List<RedissonClient> redissonClientList = new ArrayList<>(serverList.size());
        for (String server : serverList) {
            Config config = new Config();
            config.useSingleServer()
                    .setAddress(server);

            redissonClientList.add(Redisson.create(config));
        }

        List<RLock> lockList = new ArrayList<>(redissonClientList.size());
        for (RedissonClient redissonClient : redissonClientList) {
            lockList.add(redissonClient.getLock("java-lock"));
        }
        
        int threadCount = 3;
        CountDownLatch countDownLatch = new CountDownLatch(threadCount);
        ExecutorService executorService = Executors.newFixedThreadPool(threadCount);

        for (int i = 0; i < threadCount; i++) {
            executorService.submit(() -> {
                RedissonRedLock redissonRedLock = new RedissonRedLock(lockList.toArray(new RLock[0]));
                redissonRedLock.lock();
                try {
                    System.out.println(Thread.currentThread().getName() + "獲得鎖，開始執(zhí)行業(yè)務(wù)邏輯。。。");
                    try {
                        TimeUnit.SECONDS.sleep(3);
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                    System.out.println(Thread.currentThread().getName() + "獲得鎖，結(jié)束執(zhí)行業(yè)務(wù)邏輯。。。");
                    count++;
                } finally {
                    redissonRedLock.unlock();
                }
                countDownLatch.countDown();
            });
        }

        countDownLatch.await();
        executorService.shutdown();
        System.out.println(count);

        for (RedissonClient redissonClient : redissonClientList) {
            redissonClient.shutdown();
        }
    }

}