Redisson分布式锁

SpringBoot集成Redisson步骤

引入依赖

    org.redisson
    redisson
    3.6.5

初始化客户端

@Bean
public RedissonClient redisson(){
    // 单机模式
    Config config = new Config();
    config.useSingleServer().setAddress("redis://192.168.3.170:6379").setDatabase(0);
    return Redisson.create(config);
}

Redisson实现分布式锁

package com.wangcp.redisson;

import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class IndexController {

    @Autowired
    private RedissonClient redisson;
    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    /**
     * 模拟下单减库存的场景
     * @return
     */
    @RequestMapping(value = "/duduct_stock")
    public String deductStock(){
        String lockKey = "product_001";
        // 1.获取锁对象
        RLock redissonLock = redisson.getLock(lockKey);
        try{
            // 2.加锁
            redissonLock.lock();  // 等价于 setIfAbsent(lockKey,"wangcp",10,TimeUnit.SECONDS);
            // 从redis 中拿当前库存的值
            int stock = Integer.parseInt(stringRedisTemplate.opsForValue().get("stock"));
            if(stock > 0){
                int realStock = stock - 1;
                stringRedisTemplate.opsForValue().set("stock",realStock + "");
                System.out.println("扣减成功，剩余库存：" + realStock);
            }else{
                System.out.println("扣减失败，库存不足");
            }
        }finally {
            // 3.释放锁
            redissonLock.unlock();
        }
        return "end";
    }
}

Redisson 分布式锁实现原理图

image

Redisson 底层源码分析

我们点击 lock() 方法，查看源码，最终看到以下代码

 RFuture tryLockInnerAsync(long leaseTime, TimeUnit unit, long threadId, RedisStrictCommand command) {
        internalLockLeaseTime = unit.toMillis(leaseTime);

        return commandExecutor.evalWriteAsync(getName(), LongCodec.INSTANCE, command,
                  "if (redis.call('exists', KEYS[1]) == 0) then " +
                      "redis.call('hset', KEYS[1], ARGV[2], 1); " +
                      "redis.call('pexpire', KEYS[1], ARGV[1]); " +
                      "return nil; " +
                  "end; " +
                  "if (redis.call('hexists', KEYS[1], ARGV[2]) == 1) then " +
                      "redis.call('hincrby', KEYS[1], ARGV[2], 1); " +
                      "redis.call('pexpire', KEYS[1], ARGV[1]); " +
                      "return nil; " +
                  "end; " +
                  "return redis.call('pttl', KEYS[1]);",
                    Collections.