redis实现分布式锁实例分析
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1、业务场景引入
模拟一个电商系统，服务器分布式部署，系统中有一个用户下订单的接口，用户下订单之前需要获取分布式锁，然后去检查一下库存，确保库存足够了才会给用户下单，然后释放锁。
由于系统有一定的并发，所以会预先将商品的库存保存在redis中，用户下单的时候会更新redis的库存。
2、基础环境准备
2.1.准备库存数据库
-- ------------------------------ Table structure for t_goods-- ----------------------------DROP TABLE IF EXISTS `t_goods`;CREATE TABLE `t_goods` ( `goods_id` int(11) NOT NULL AUTO_INCREMENT, `goods_name` varchar(255) DEFAULT NULL, `goods_price` decimal(10,2) DEFAULT NULL, `goods_stock` int(11) DEFAULT NULL, `goods_img` varchar(255) DEFAULT NULL, PRIMARY KEY (`goods_id`)) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;-- ------------------------------ Records of t_goods-- ----------------------------INSERT INTO `t_goods` VALUES ('1', 'iphone8', '6999.00', '5000', 'img/iphone.jpg');INSERT INTO `t_goods` VALUES ('2', '小米9', '3000.00', '5000', 'img/rongyao.jpg');INSERT INTO `t_goods` VALUES ('3', '华为p30', '4000.00', '5000', 'img/huawei.jpg');2.2.创建SpringBoot工程，pom.xml中导入依赖，请注意版本。
<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.springlock.task</groupId> <artifactId>springlock.task</artifactId> <version>1.0-SNAPSHOT</version> <!--导入SpringBoot的父工程 把系统中的版本号做了一些定义！ --> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.1.3.RELEASE</version> </parent> <dependencies> <!--导入SpringBoot的Web场景启动器 Web相关的包导入！--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!--导入MyBatis的场景启动器--> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>2.0.0</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid-spring-boot-starter</artifactId> <version>1.1.10</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.28</version> </dependency> <!--SpringBoot单元测试--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <!--导入Lombok依赖--> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> </dependency> <!--Spring Data Redis 的启动器 --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency> <dependency> <groupId>redis.clients</groupId> <artifactId>jedis</artifactId> <version>2.9.0</version> </dependency> </dependencies> <build> <!--编译的时候同时也把包下面的xml同时编译进去--> <resources> <resource> <directory>class="lazy" data-src/main/java</directory> <includes> <include>**@SpringBootApplicationpublic class SpringLockApplicationApp { public static void main(String[] args) { SpringApplication.run(SpringLockApplicationApp.class,args); }}2.5.添加Redis的配置类
import com.fasterxml.jackson.annotation.JsonAutoDetect;import com.fasterxml.jackson.annotation.PropertyAccessor;import com.fasterxml.jackson.databind.ObjectMapper;import lombok.extern.slf4j.Slf4j;import org.springframework.boot.context.properties.ConfigurationProperties;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;import org.springframework.data.redis.core.RedisTemplate;import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;import org.springframework.data.redis.serializer.StringRedisSerializer;import redis.clients.jedis.JedisPoolConfig;@Slf4j@Configurationpublic class RedisConfig { @Bean @ConfigurationProperties(prefix="spring.redis.jedis.pool") public JedisPoolConfig jedisPoolConfig(){ JedisPoolConfig config = new JedisPoolConfig(); log.info("JedisPool默认参数-最大空闲数:{},最小空闲数:{},最大链接数:{}",config.getMaxIdle(),config.getMinIdle(),config.getMaxTotal()); return config; } @Bean @ConfigurationProperties(prefix="spring.redis") public JedisConnectionFactory jedisConnectionFactory(JedisPoolConfig config){ log.info("redis初始化配置-最大空闲数:{},最小空闲数:{},最大链接数:{}",config.getMaxIdle(),config.getMinIdle(),config.getMaxTotal()); JedisConnectionFactory factory = new JedisConnectionFactory(); //关联链接池的配置对象 factory.setPoolConfig(config); return factory; } @Bean public RedisTemplate<String,Object> redisTemplate(JedisConnectionFactory factory){ RedisTemplate<String, Object> template = new RedisTemplate<>(); //关联 template.setConnectionFactory(factory); //使用Jackson2JsonRedisSerializer来序列化和反序列化redis的value值（默认使用JDK的序列化方式） Jackson2JsonRedisSerializer jacksonSeial = new Jackson2JsonRedisSerializer(Object.class); ObjectMapper om = new ObjectMapper(); //指定要序列化的域，field,get和set,以及修饰符范围，ANY是都有包括private和public om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY); //指定序列化输入的类型，类必须是非final修饰的，final修饰的类，比如String,Integer等会跑出异常 om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL); jacksonSeial.setObjectMapper(om); //使用StringRedisSerializer来序列化和反序列化redis的key值 template.setKeySerializer(new StringRedisSerializer()); //值采用json序列化 template.setValueSerializer(jacksonSeial); //设置hash key 和value序列化模式 template.setHashKeySerializer(new StringRedisSerializer()); template.setHashValueSerializer(jacksonSeial); return template; }}2.6.pojo层
import lombok.AllArgsConstructor;import lombok.Data;import lombok.NoArgsConstructor;@Data@NoArgsConstructor@AllArgsConstructorpublic class Goods { private String goods_id; private String goods_name; private Double goods_price; private Long goods_stock; private String goods_img;}2.7.mapper层
import com.springlock.pojo.Goods;import org.apache.ibatis.annotations.Mapper;import org.apache.ibatis.annotations.Select;import org.apache.ibatis.annotations.Update;import java.util.List;@Mapperpublic interface GoodsMapper { @Update("update t_goods set goods_stock=#{goods_stock} where goods_id=#{goods_id}") Integer updateGoodsStock(Goods goods); @Select("select * from t_goods") List<Goods> findGoods(); @Select("select * from t_goods where goods_id=#{goods_id}") Goods findGoodsById(String goodsId);}2.8.SpringBoot监听Web启动事件，加载商品数据到Redis中
import com.springlock.mapper.GoodsMapper;import com.springlock.pojo.Goods;import lombok.extern.slf4j.Slf4j;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.ApplicationListener;import org.springframework.context.annotation.Configuration;import org.springframework.context.event.ContextRefreshedEvent;import org.springframework.data.redis.core.RedisTemplate;import javax.annotation.Resource;import java.util.List;@Slf4j@Configurationpublic class ApplicationStartListener implements ApplicationListener<ContextRefreshedEvent> { @Resource GoodsMapper goodsMapper; @Autowired private RedisTemplate<String, Object> redisTemplate; @Override public void onApplicationEvent(ContextRefreshedEvent event) { System.out.println("Web项目启动,ApplicationListener监听器触发..."); List<Goods> goodsList = goodsMapper.findGoods(); for (Goods goods : goodsList) { redisTemplate.boundHashOps("goods_info").put(goods.getGoods_id(), goods.getGoods_stock()); log.info("缓存商品详情:{}",goods); } }}3、Redis实现分布式锁
3.1 分布式锁的实现类
import redis.clients.jedis.Jedis;import redis.clients.jedis.JedisPool;import redis.clients.jedis.JedisPoolConfig;import redis.clients.jedis.Transaction;import redis.clients.jedis.exceptions.JedisException;import java.util.List;import java.util.UUID;public class DistributedLock { //redis连接池 private static JedisPool jedisPool; static { JedisPoolConfig config = new JedisPoolConfig(); // 设置最大连接数 config.setMaxTotal(200); // 设置最大空闲数 config.setMaxIdle(8); // 设置最大等待时间 config.setMaxWaitMillis(1000 * 100); // 在borrow一个jedis实例时，是否需要验证，若为true，则所有jedis实例均是可用的 config.setTestOnBorrow(true); jedisPool = new JedisPool(config, "192.168.3.28", 6379, 3000); } public String lockWithTimeout(String lockName, long acquireTimeout, long timeout) { Jedis conn = null; String retIdentifier = null; try { // 获取连接 conn = jedisPool.getResource(); // value值->随机生成一个String String identifier = UUID.randomUUID().toString(); // key值->即锁名 String lockKey = "lock:" + lockName; // 超时时间->上锁后超过此时间则自动释放锁 毫秒转成->秒 int lockExpire = (int) (timeout / 1000); // 获取锁的超时时间->超过这个时间则放弃获取锁 long end = System.currentTimeMillis() + acquireTimeout; while (System.currentTimeMillis() < end) { //在获取锁时间内 if (conn.setnx(lockKey, identifier) == 1) {//设置锁成功 conn.expire(lockKey, lockExpire); // 返回value值，用于释放锁时间确认 retIdentifier = identifier; return retIdentifier; } // ttl以秒为单位返回 key 的剩余过期时间，返回-1代表key没有设置超时时间，为key设置一个超时时间 if (conn.ttl(lockKey) == -1) { conn.expire(lockKey, lockExpire); } try { Thread.sleep(10); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } catch (JedisException e) { e.printStackTrace(); } finally { if (conn != null) { conn.close(); } } return retIdentifier; } public boolean releaseLock(String lockName, String identifier) { Jedis conn = null; String lockKey = "lock:" + lockName; boolean retFlag = false; try { conn = jedisPool.getResource(); while (true) { // 监视lock，准备开始redis事务 conn.watch(lockKey); // 通过前面返回的value值判断是不是该锁，若是该锁，则删除，释放锁 if (identifier.equals(conn.get(lockKey))) { Transaction transaction = conn.multi();//开启redis事务 transaction.del(lockKey); List<Object> results = transaction.exec();//提交redis事务 if (results == null) {//提交失败 continue;//继续循环 } retFlag = true;//提交成功 } conn.unwatch();//解除监控 break; } } catch (JedisException e) { e.printStackTrace(); } finally { if (conn != null) { conn.close(); } } return retFlag; }}3.2 分布式锁的业务代码
service业务逻辑层
public interface SkillService { Integer seckill(String goodsId,Long goodsStock);}service业务逻辑层实现层
import com.springlock.lock.DistributedLock;import com.springlock.mapper.GoodsMapper;import com.springlock.pojo.Goods;import com.springlock.service.SkillService;import lombok.extern.slf4j.Slf4j;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.data.redis.core.RedisTemplate;import org.springframework.stereotype.Service;import javax.annotation.Resource;@Slf4j@Servicepublic class SkillServiceImpl implements SkillService { private final DistributedLock lock = new DistributedLock(); private final static String LOCK_NAME = "goods_stock_resource"; @Resource GoodsMapper goodsMapper; @Autowired private RedisTemplate<String, Object> redisTemplate; @Override public Integer seckill(String goodsId, Long goodsQuantity) { // 加锁，返回锁的value值，供释放锁时候进行判断 String identifier = lock.lockWithTimeout(LOCK_NAME, 5000, 1000); Integer goods_stock = (Integer) redisTemplate.boundHashOps("goods_info").get(goodsId); if (goods_stock > 0 && goods_stock >= goodsQuantity) { //1.查询数据库对象 Goods goods = goodsMapper.findGoodsById(goodsId); //2.更新数据库中库存数量 goods.setGoods_stock(goods.getGoods_stock() - goodsQuantity); goodsMapper.updateGoodsStock(goods); //3.同步Redis中商品库存 redisTemplate.boundHashOps("goods_info").put(goods.getGoods_id(), goods.getGoods_stock()); log.info("商品Id:{},在Redis中剩余库存数量:{}", goodsId, goods.getGoods_stock()); //释放锁 lock.releaseLock(LOCK_NAME, identifier); return 1; } else { log.info("商品Id:{},库存不足！,库存数：{},购买量：{}", goodsId, goods_stock, goodsQuantity); //释放锁 lock.releaseLock(LOCK_NAME, identifier); return -1; } }}controller层
import com.springlock.service.SkillService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.annotation.Scope;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;@RestController@Scope("prototype") //prototype 多实例，singleton单实例public class SkillController { @Autowired SkillService skillService; @RequestMapping("/skill") public String skill() { Integer count = skillService.seckill("1", 1L); return count > 0 ? "下单成功" + count : "下单失败" + count; }}4、分布式锁测试
把SpringBoot工程启动两台服务器，端口分别为8888、9999。启动8888端口后，修改配置文件端口为9999，启动另一个应用
然后使用jmeter进行并发测试，开两个线程组，分别代表两台服务器下单，1秒钟起20个线程，循环25次，总共下单1000次。
查看控制台输出：
注意：该锁在并发量太高的情况下，会出现一部分失败率。手动写的程序，因为操作的非原子性，会存在并发问题。该锁的实现只是为了演示原理，并不适用于生产。
jmeter聚合报告
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