第十九章_手写Redis分布式锁

锁的种类

单机版同一个JVM虚拟机内synchronized或者Lock接口。

分布式多个不同JVM虚拟机，单机的线程锁机制不再起作用，资源类在不同的服务器之间共享了。

一个靠谱分布式锁需要具备的条件和刚需

独占性 ：OnlyOne，任何时刻只能有且仅有一个线程持有。

高可用：若redis集群环境下，不能因为某一个节点挂了而出现获取锁和释放锁失败的情况，高并发请求下，依旧性能OK好使。（redis集群为cp模式，zookeeper集群为ap模式）

防死锁：杜绝死锁，必须有超时控制机制或者撤销操作，有个兜底终止跳出方案。

不乱抢：防止张冠李戴，不能私下unlock别人的锁，只能自己加锁自己释放，自己约的锁含着泪也要自己解。

重入性：同一个节点的同一个线程如果获得锁之后，它也可以再次获取这个锁。

分布式锁

setnx key value 

差评，setnx+expire不安全，两条命令非原子性的。

set key value [EX seconds] [PX milliseconds] [NX|XX]。

重点

JUC中AQS锁的规范落地参考+可重入锁考虑+Lua脚本+Redis命令一步步实现分布式锁。

Base案例(boot+redis)

使用场景：多个服务间保证同一时刻同一时间段内同一用户只能有一个请求(防止关键业务出现并发攻击)。

建Module

redis_distributed_lock2、redis_distributed_lock3

改POM

<?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.test.redislock</groupId><artifactId>redis_distributed_lock2</artifactId><version>1.0-SNAPSHOT</version><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.6.12</version><relativePath/> <!-- lookup parent from repository --></parent><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target><lombok.version>1.16.18</lombok.version></properties><dependencies><!--SpringBoot通用依赖模块--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!--SpringBoot与Redis整合依赖--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId></dependency><dependency><groupId>org.apache.commons</groupId><artifactId>commons-pool2</artifactId></dependency><!--swagger2--><dependency><groupId>io.springfox</groupId><artifactId>springfox-swagger2</artifactId><version>2.9.2</version></dependency><dependency><groupId>io.springfox</groupId><artifactId>springfox-swagger-ui</artifactId><version>2.9.2</version></dependency><!--通用基础配置boottest/lombok/hutool--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>${lombok.version}</version><optional>true</optional></dependency><dependency><groupId>cn.hutool</groupId><artifactId>hutool-all</artifactId><version>5.8.8</version></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

写YML

server.port=7777spring.application.name=redis_distributed_lock
# ========================swagger2=====================
# http://localhost:7777/swagger-ui.html
swagger2.enabled=true
spring.mvc.pathmatch.matching-strategy=ant_path_matcher# ========================redis单机=====================
spring.redis.database=0
spring.redis.host=192.168.111.185
spring.redis.port=6379
spring.redis.password=111111
spring.redis.lettuce.pool.max-active=8
spring.redis.lettuce.pool.max-wait=-1ms
spring.redis.lettuce.pool.max-idle=8
spring.redis.lettuce.pool.min-idle=0

主启动

package com.test.redislock;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;/*** @auther admin*/
@SpringBootApplication
public class RedisDistributedLockApp7777 {public static void main(String[] args) {SpringApplication.run(RedisDistributedLockApp7777.class,args);}}

业务类

Swagger2Config

package com.test.redislock.config;import org.springframework.beans.BeansException;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping;
import springfox.documentation.builders.ApiInfoBuilder;
import springfox.documentation.builders.PathSelectors;
import springfox.documentation.builders.RequestHandlerSelectors;
import springfox.documentation.service.ApiInfo;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;
import springfox.documentation.spring.web.plugins.WebMvcRequestHandlerProvider;
import springfox.documentation.swagger2.annotations.EnableSwagger2;import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.List;
import java.util.stream.Collectors;/*** @auther admin*/
@Configuration
@EnableSwagger2
public class Swagger2Config {@Value("${swagger2.enabled}")private Boolean enabled;@Beanpublic Docket createRestApi() {return new Docket(DocumentationType.SWAGGER_2).apiInfo(apiInfo()).enable(enabled).select()//你自己的package.apis(RequestHandlerSelectors.basePackage("com.test.redislock")) .paths(PathSelectors.any()).build();}private ApiInfo apiInfo() {return new ApiInfoBuilder().title("springboot利用swagger2构建api接口文档 " + "\t" + DateTimeFormatter.ofPattern("yyyy-MM-dd").format(LocalDateTime.now())).description("springboot+redis整合").version("1.0").termsOfServiceUrl("https://www.baidu.com/").build();}}

RedisConfig

package com.test.redislock.config;import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;/*** @auther admin*/
@Configuration
public class RedisConfig {@Beanpublic RedisTemplate<String, Object> redisTemplate(LettuceConnectionFactory lettuceConnectionFactory) {RedisTemplate<String,Object> redisTemplate = new RedisTemplate<>();redisTemplate.setConnectionFactory(lettuceConnectionFactory);//设置key序列化方式stringredisTemplate.setKeySerializer(new StringRedisSerializer());//设置value的序列化方式jsonredisTemplate.setValueSerializer(new GenericJackson2JsonRedisSerializer());redisTemplate.setHashKeySerializer(new StringRedisSerializer());redisTemplate.setHashValueSerializer(new GenericJackson2JsonRedisSerializer());redisTemplate.afterPropertiesSet();return redisTemplate;}}

InventoryService

package com.test.redislock.service;/*** @auther admin*/
public class InventoryService {/*** 模拟商品库存扣减*/String sale();}

InventoryServiceImpl

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;private Lock lock = new ReentrantLock();/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";lock.lock();try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if(inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {lock.unlock();}return retMessage + "\t" + "服务端口号：" + port;}}

InventoryController

package com.test.redislock.controller;import cn.hutool.core.util.IdUtil;
import com.test.redislock.service.InventoryService;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import lombok.Getter;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;import java.util.concurrent.atomic.AtomicInteger;/*** @auther admin*/
@RestController
@Api(tags = "redis分布式锁测试")
public class InventoryController {@Autowiredprivate InventoryService inventoryService;@ApiOperation("扣减库存，一次卖一个")@GetMapping(value = "/inventory/sale")public String sale() {return inventoryService.sale();}}

使用swagger进行测试

http://localhost:7777/swagger-ui.html#/

手写分布式锁思路分析2023

大家来找茬 

上面测试通过求吐槽

1.初始化版本简单添加

InventoryServiceImpl

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;private Lock lock = new ReentrantLock();/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";lock.lock();try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if(inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {lock.unlock();}return retMessage + "\t" + "服务端口号："+port;}
}

请将端口7777的业务逻辑代码原样拷贝到端口8888

加了synchronized或者Lock。

2.nginx分布式微服务架构

问题

V2.0版本代码分布式部署后，单机锁还是出现超卖现象，需要分布式锁。

Nginx配置负载均衡

命令地址+配置地址

命令地址

/usr/local/nginx/sbin

配置地址

/usr/local/nginx/conf

启动

cd /usr/local/nginx/sbin

./nginx

启动Nginx并测试通过，浏览器看到nginx欢迎welcome页面

/usr/local/nginx/conf目录下修改配置文件，nginx.conf新增反向代理和负载均衡配置

关闭

cd /usr/local/nginx/sbin

./nginx -s stop

指定配置启动

在/usr/local/nginx/sbin路径下执行下面的命令

./nginx -c /usr/local/nginx/conf/nginx.conf

重启

cd /usr/local/nginx/sbin

./nginx -s reload

V2.0版本代码修改+启动两个微服务

端口7777服务

InventoryServiceImpl

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;private Lock lock = new ReentrantLock();/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";lock.lock();try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if(inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {lock.unlock();}return retMessage + "\t" + "服务端口号：" + port;}}

端口8888服务

InventoryServiceImpl

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;private Lock lock = new ReentrantLock();/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";lock.lock();try{//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if(inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: "+inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {lock.unlock();}return retMessage + "\t" + "服务端口号：" + port;}}

通过Nginx访问，Linux服务器地址IP，反向代理+负载均衡

可以点击看到效果，一边一个，默认轮询

http://192.168.111.185/inventory/sale

上面纯手点验证OK，下面高并发模拟

线程组redis

100个商品足够了

http请求

jmeter压测 

76号商品被卖出2次，出现超卖故障现象

bug-why

为什么加了synchronized或者Lock还是没有控制住？

解释

在单机环境下，可以使用synchronized或Lock来实现。

但是在分布式系统中，因为竞争的线程可能不在同一个节点上（同一个jvm中），

所以需要一个让所有进程都能访问到的锁来实现(比如redis或者zookeeper来构建)

不同进程jvm层面的锁就不管用了，那么可以利用第三方的一个组件，来获取锁，未获取到锁，则阻塞当前想要运行的线程。

分布式锁出现

能做什么

跨进程+跨服务

解决超卖

防止缓存击穿

解决方案

上Redis分布式锁

官网命令

3.redis分布式锁

修改代码为3.1版

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";String key = "zzyyRedisLock";String uuidValue = IdUtil.simpleUUID() + ":" + Thread.currentThread().getId();Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, uuidValue);if (!flag) {//暂停20毫秒后递归调用try { TimeUnit.MILLISECONDS.sleep(20); } catch (InterruptedException e) { e.printStackTrace(); }sale();} else {try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {stringRedisTemplate.delete(key);}}return retMessage + "\t" + "服务端口号：" + port;}}

通过递归重试的方式。

存在的问题

测试手工OK，测试Jmeter压测5000OK。

递归是一种思想没错，但是容易导致StackOverflowError，不太推荐，需进一步完善。

修改代码为3.2版

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.TimeUnit;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";String key = "zzyyRedisLock";String uuidValue = IdUtil.simpleUUID() + ":" + Thread.currentThread().getId();while (!stringRedisTemplate.opsForValue().setIfAbsent(key, uuidValue)) {//暂停20毫秒，类似CAS自旋try { TimeUnit.MILLISECONDS.sleep(20);} catch (InterruptedException e) {e.printStackTrace();}}try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {stringRedisTemplate.delete(key);}return retMessage + "\t" + "服务端口号：" + port;}}

多线程判断想想JUC里面说过的虚假唤醒，用while替代if。

用自旋替代递归重试。

4.宕机与过期+防止死锁

当前代码为3.2版接上一步

存在问题

部署了微服务的Java程序机器挂了，代码层面根本没有走到finally这块，没办法保证解锁(无过期时间该key一直存在)，这个key没有被删除，需要加入一个过期时间限定key。

解决方案

修改代码为4.1版

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";String key = "zzyyRedisLock";String uuidValue = IdUtil.simpleUUID() + ":" + Thread.currentThread().getId();while (!stringRedisTemplate.opsForValue().setIfAbsent(key, uuidValue)) {//暂停20毫秒，类似CAS自旋try { TimeUnit.MILLISECONDS.sleep(20);} catch (InterruptedException e) {e.printStackTrace();}}//设置过期时间，请思考可以这么操作吗?stringRedisTemplate.expire(key, 30L, TimeUnit.SECONDS);try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {stringRedisTemplate.delete(key);}return retMessage + "\t" + "服务端口号：" + port;}}

stringRedisTemplate.expire(key,30L,TimeUnit.SECONDS);

请思考可以这么操作吗?

4.1版本结论

设置key+过期时间分开了，必须要合并成一行具备原子性

修改代码为4.2版

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";String key = "zzyyRedisLock";String uuidValue = IdUtil.simpleUUID() + ":" + Thread.currentThread().getId();//设置过期时间，形成原子操作while (!stringRedisTemplate.opsForValue().setIfAbsent(key, uuidValue, 30L, TimeUnit.SECONDS)) {//暂停20毫秒，类似CAS自旋try { TimeUnit.MILLISECONDS.sleep(20);} catch (InterruptedException e) {e.printStackTrace();}}try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {stringRedisTemplate.delete(key);}return retMessage + "\t" + "服务端口号：" + port;}}

 Jmeter压测OK

4.2版本结论

加锁和过期时间设置必须同一行，保证原子性

5.防止误删key的问题

当前代码为4.2版接上一步

存在问题

实际业务处理时间如果超过了默认设置key的过期时间？？尴尬￣□￣｜｜

会出现张冠李戴的情况，删除了别人的锁。

解决方案

只能自己删除自己的，不许动别人的

修改代码为5.0版

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";String key = "zzyyRedisLock";String uuidValue = IdUtil.simpleUUID() + ":" + Thread.currentThread().getId();//设置过期时间，形成原子操作while (!stringRedisTemplate.opsForValue().setIfAbsent(key, uuidValue, 30L, TimeUnit.SECONDS)) {//暂停20毫秒，类似CAS自旋try { TimeUnit.MILLISECONDS.sleep(20);} catch (InterruptedException e) {e.printStackTrace();}}try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {// v5.0判断加锁与解锁是不是同一个客户端，同一个才行，自己只能删除自己的锁，不误删他人的if (stringRedisTemplate.opsForValue().get(key).equalsIgnoreCase(uuidValue)) {stringRedisTemplate.delete(key);}}return retMessage + "\t" + "服务端口号：" + port;}}

6.Lua保证原子性

当前代码为5.0版接上一步

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";String key = "zzyyRedisLock";String uuidValue = IdUtil.simpleUUID() + ":" + Thread.currentThread().getId();//设置过期时间，形成原子操作while (!stringRedisTemplate.opsForValue().setIfAbsent(key, uuidValue, 30L, TimeUnit.SECONDS)) {//暂停20毫秒，类似CAS自旋try { TimeUnit.MILLISECONDS.sleep(20);} catch (InterruptedException e) {e.printStackTrace();}}try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {// v5.0判断加锁与解锁是不是同一个客户端，同一个才行，自己只能删除自己的锁，不误删他人的if (stringRedisTemplate.opsForValue().get(key).equalsIgnoreCase(uuidValue)) {stringRedisTemplate.delete(key);}}return retMessage + "\t" + "服务端口号：" + port;}}

存在问题

finally块的判断+del删除操作不是原子性的

启用lua脚本编写redis分布式锁判断+删除判断代码

lua脚本

官网

官方脚本

Lua脚本浅谈

Lua脚本初识

Redis调用Lua脚本通过eval命令保证代码执行的原子性，直接用return返回脚本执行后的结果值

语法：eval luascript numkeys [key [key ...]] [arg [arg ...]]

helloworld入门 

1-hello lua

2-set k1 v1 get k1

3-mset 

Lua脚本进一步

Redis分布式锁lua脚本官网练习

eval "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end" 1 zzyyRedisLock 1111-2222-3333

条件判断语法

条件判断案例

解决方案

修改代码为6.0版code

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import java.util.concurrent.locks.Lock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";String key = "zzyyRedisLock";String uuidValue = IdUtil.simpleUUID() + ":" + Thread.currentThread().getId();//设置过期时间，形成原子操作while (!stringRedisTemplate.opsForValue().setIfAbsent(key, uuidValue, 30L, TimeUnit.SECONDS)) {//暂停20毫秒，类似CAS自旋try { TimeUnit.MILLISECONDS.sleep(20);} catch (InterruptedException e) {e.printStackTrace();}}try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} finally {//V6.0 将判断+删除自己的合并为lua脚本保证原子性String luaScript ="if (redis.call('get', KEYS[1]) == ARGV[1]) then " +"return redis.call('del', KEYS[1]) " +"else " +"return 0 " +"end";stringRedisTemplate.execute(new DefaultRedisScript<>(luaScript, Boolean.class), Arrays.asList(key), uuidValue);}return retMessage + "\t" + "服务端口号：" + port;}}

 bug说明

stringRedisTemplate.execute( new DefaultRedisScript<>(script), Arrays. asList(key),value);

stringRedisTemplate.execute( new DefaultRedisScript<>(script, Long.class), Arrays. asList(key),value); //使用该构造方法，不然报错

 7.可重入锁+设计模式

当前代码为6.0版接上一步

while判断并自旋重试获取锁+setnx含自然过期时间+Lua脚本官网删除锁命令。

存在问题

如何兼顾锁的可重入性问题？

复习写好一个锁的条件和规约

可重入锁(又名递归锁)

说明

可重入锁又名递归锁

是指在同一个线程在外层方法获取锁的时候，再进入该线程的内层方法会自动获取锁(前提，锁对象得是同一个对象)，不会因为之前已经获取过还没释放而阻塞。

如果是1个有 synchronized 修饰的递归调用方法，程序第2次进入被自己阻塞了岂不是天大的笑话，出现了作茧自缚。

所以Java中ReentrantLock和synchronized都是可重入锁，可重入锁的一个优点是可一定程度避免死锁。

“可重入锁”这四个字分开来解释：

可：可以。

重：再次。

入：进入。

锁：同步锁。

进入什么

进入同步域（即同步代码块/方法或显式锁锁定的代码）

一句话

一个线程中的多个流程可以获取同一把锁，持有这把同步锁可以再次进入。自己可以获取自己的内部锁。

JUC知识复习，可重入锁出bug会如何影响程序？

可重入锁种类

隐式锁（即synchronized关键字使用的锁）默认是可重入锁。

指的是可重复可递归调用的锁，在外层使用锁之后，在内层仍然可以使用，并且不发生死锁，这样的锁就叫做可重入锁。

简单的来说就是：在一个synchronized修饰的方法或代码块的内部调用本类的其他synchronized修饰的方法或代码块时，是永远可以得到锁的

与可重入锁相反，不可重入锁不可递归调用，递归调用就发生死锁。

同步块

package com.test.juc.senior.prepare;/*** @auther admin*/
public class ReEntryLockDemo {public static void main(String[] args) {final Object objectLockA = new Object();new Thread(() -> {synchronized (objectLockA) {System.out.println("-----外层调用");synchronized (objectLockA) {System.out.println("-----中层调用");synchronized (objectLockA) {System.out.println("-----内层调用");}}}}, "a").start();}
}

 同步方法

package com.test.juc.senior.prepare;/*** @auther admin* 在一个Synchronized修饰的方法或代码块的内部调用本类的其他Synchronized修饰的方法或代码块时，是永远可以得到锁的*/
public class ReEntryLockDemo {public synchronized void m1() {System.out.println("-----m1");m2();}public synchronized void m2() {System.out.println("-----m2");m3();}public synchronized void m3() {System.out.println("-----m3");}public static void main(String[] args) {ReEntryLockDemo reEntryLockDemo = new ReEntryLockDemo();reEntryLockDemo.m1();}}

Synchronized的重入的实现机理

每个锁对象拥有一个锁计数器和一个指向持有该锁的线程的指针。

当执行monitorenter时，如果目标锁对象的计数器为零，那么说明它没有被其他线程所持有，Java虚拟机会将该锁对象的持有线程设置为当前线程，并且将其计数器加1。

在目标锁对象的计数器不为零的情况下，如果锁对象的持有线程是当前线程，那么 Java 虚拟机可以将其计数器加1，否则需要等待，直至持有线程释放该锁。

当执行monitorexit时，Java虚拟机则需将锁对象的计数器减1。计数器为零代表锁已被释放。

显式锁（即Lock）也有ReentrantLock这样的可重入锁。

package com.test.juc.senior.prepare;import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;/*** @auther admin* 在一个Synchronized修饰的方法或代码块的内部调用本类的其他Synchronized修饰的方法或代码块时，是永远可以得到锁的*/
public class ReEntryLockDemo {static Lock lock = new ReentrantLock();public static void main(String[] args) {new Thread(() -> {lock.lock();try {System.out.println("----外层调用lock");lock.lock();try {System.out.println("----内层调用lock");} finally {// 这里故意注释，实现加锁次数和释放次数不一样// 由于加锁次数和释放次数不一样，第二个线程始终无法获取到锁，导致一直在等待。// 正常情况，加锁几次就要解锁几次lock.unlock(); }} finally {lock.unlock();}}, "a").start();new Thread(() -> {lock.lock();try {System.out.println("b thread----外层调用lock");} finally {lock.unlock();}}, "b").start();}
}

lock/unlock配合可重入锁进行AQS源码分析讲解

切记，一般而言，你lock了几次就要unlock几次

思考，上述可重入锁计数问题，redis中那个数据类型可以代替

K，K，V

hset  zzyyRedisLock 29f0ee01ac77414fb8b0861271902a94:1

Map<String, Map<Object, Object>>

案例命令

hset key field value

hset redis锁名字(zzyyRedisLock)  某个请求线程的UUID+ThreadID  加锁的次数

小总结

setnx，只能解决有无的问题，够用但是不完美。

hset，不但解决有无，还解决可重入问题。

思考+设计重点(一横一纵)

目前有2条支线，目的是保证同一个时候只能有一个线程持有锁进去redis做扣减库存动作。

2个分支

1.保证加锁/解锁，lock/unlock

2.扣减库存redis命令的原子性

lua脚本 

redis命令过程分析

加锁lua脚本lock

先判断redis分布式锁这个key是否存在

EXISTS key

返回零说明不存在，hset新建当前线程属于自己的锁BY UUID:ThreadID

HSET zzyyRedisLock 0c90d37cb6ec42268861b3d739f8b3a8:1      1

命令       key                value = UUID:ThreadID                                 次数

返回壹说明已经有锁，需进一步判断是不是当前线程自己的

HEXISTS key uuid:ThreadID

HEXISTS zzyyRedisLock 0c90d37cb6ec42268861b3d739f8b3a8:1

返回零说明不是自己的返回壹说明是自己的锁，自增1次表示重入

HINCRBY key field increment

HINCRBY zzyyRedisLock 0c90d37cb6ec42268861b3d739f8b3a8:1 1

将上述设计修改为Lua脚本

V1

if redis.call('exists', 'key') == 0 thenredis.call('hset', 'key', 'uuid:threadid', 1)redis.call('expire', 'key', 30)return 1elseif redis.call('hexists', 'key', 'uuid:threadid') == 1 thenredis.call('hincrby', 'key', 'uuid:threadid', 1)redis.call('expire', 'key', 30)return 1elsereturn 0end

相同部分是否可以替换处理？？？

hincrby命令可否替代hset命令

相同部分是否可以替换处理？？？

V2

if redis.call('exists', 'key') == 0 or redis.call('hexists', 'key', 'uuid:threadid') == 1 thenredis.call('hincrby', 'key', 'uuid:threadid', 1)redis.call('expire', 'key', 30)return 1elsereturn 0end

V3

key	KEYS[1]	zzyyRedisLock
value	ARGV[1]	2f586ae740a94736894ab9d51880ed9d:1
过期时间值	ARGV[2]	30   秒

if redis.call('exists', KEYS[1]) == 0 or redis.call('hexists', KEYS[1], ARGV[1]) == 1 then redis.call('hincrby', KEYS[1], ARGV[1], 1) redis.call('expire', KEYS[1], ARGV[2]) return 1 elsereturn 0end

 测试

EVAL "if redis.call('exists',KEYS[1]) == 0 or redis.call('hexists',KEYS[1],ARGV[1]) == 1 then redis.call('hincrby',KEYS[1],ARGV[1],1) redis.call('expire',KEYS[1],ARGV[2]) return 1 else return 0 end" 1 zzyyRedisLock 0c90d37cb6ec42268861b3d739f8b3a8:1 30

HGET zzyyRedisLock 0c90d37cb6ec42268861b3d739f8b3a8:1

解锁lua脚本unlock

设计思路：有锁且还是自己的锁

HEXISTS key uuid:ThreadID

HEXISTS zzyyRedisLock 0c90d37cb6ec42268861b3d739f8b3a8:1

返回零，说明根本没有锁，程序块返回nil，不是零，说明有锁且是自己的锁，直接调用HINCRBY 负一 表示每次减个一，解锁一次。直到它变为零表示可以删除该锁Key，del 锁key。

全套流程

上述设计修改为Lua脚本

V1

if redis.call('HEXISTS', lock, uuid:threadID) == 0 thenreturn nilelseif redis.call('HINCRBY', lock, uuid:threadID, -1) == 0 thenreturn redis.call('del', lock)else return 0end

 V2

if redis.call('HEXISTS', KEYS[1], ARGV[1]) == 0 thenreturn nilelseif redis.call('HINCRBY', KEYS[1], ARGV[1], -1) == 0 thenreturn redis.call('del', KEYS[1])elsereturn 0end

eval "if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 0 then return nil elseif redis.call('HINCRBY',KEYS[1],ARGV[1],-1) == 0 then return redis.call('del',KEYS[1]) else return 0 end" 1 zzyyRedisLock 2f586ae740a94736894ab9d51880ed9d:1

测试全套流程

将上述lua脚本整合进入微服务Java程序 

复原程序为初始无锁版

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: "+inventoryNumber + "\t";System.out.println(retMessage);} else{retMessage = "商品卖完了，o(╥﹏╥)o";}return retMessage + "\t" + "服务端口号：" + port;}
}

新建RedisDistributedLock类并实现JUC里面的Lock接口

满足JUC里面AQS对Lock锁的接口规范定义来进行实现落地代码

结合设计模式开发属于自己的Redis分布式锁工具类

lock方法的全盘通用讲解

lua脚本

加锁lock

if redis.call('exists', KEYS[1]) == 0 or redis.call('hexists', KEYS[1], ARGV[1]) == 1 then redis.call('hincrby', KEYS[1], ARGV[1], 1) redis.call('expire', KEYS[1], ARGV[2]) return 1 elsereturn 0end

解锁unlock

if redis.call('HEXISTS', KEYS[1], ARGV[1]) == 0 then return nil elseif redis.call('HINCRBY', KEYS[1], ARGV[1], -1) == 0 then return redis.call('del', KEYS[1]) else return 0end

工厂设计模式引入

通过实现JUC里面的Lock接口，实现Redis分布式锁RedisDistributedLock。

package com.test.redislock.mylock;import cn.hutool.core.util.IdUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.data.redis.support.collections.DefaultRedisList;
import org.springframework.stereotype.Component;import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;/*** @auther admin*/
//@Component 引入DistributedLockFactory工厂模式，从工厂获得而不再从spring拿到
public class RedisDistributedLock implements Lock {private StringRedisTemplate stringRedisTemplate;//KEYS[1]private String lockName;//ARGV[1]private String uuidValue;//ARGV[2]private long   expireTime;public RedisDistributedLock(StringRedisTemplate stringRedisTemplate, String lockName) {this.stringRedisTemplate = stringRedisTemplate;this.lockName = lockName;//UUID:ThreadIDthis.uuidValue = IdUtil.simpleUUID() + ":" + Thread.currentThread().getId();this.expireTime = 30L;}@Overridepublic void lock() {tryLock();}@Overridepublic boolean tryLock() {try {tryLock(-1L, TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();}return false;}/*** 干活的，实现加锁功能，实现这一个干活的就OK，全盘通用* @param time 过期时间* @param unit 单位* @return 是否获取锁* @throws InterruptedException 异常*/@Overridepublic boolean tryLock(long time, TimeUnit unit) throws InterruptedException{if (time != -1L) {this.expireTime = unit.toSeconds(time);}String script ="if redis.call('exists', KEYS[1]) == 0 or redis.call('hexists', KEYS[1], ARGV[1]) == 1 then " +"redis.call('hincrby', KEYS[1], ARGV[1], 1) " +"redis.call('expire', KEYS[1], ARGV[2]) " +"return 1 " +"else " +"return 0 " +"end";System.out.println("script: " + script);System.out.println("lockName: " + lockName);System.out.println("uuidValue: " + uuidValue);System.out.println("expireTime: " + expireTime);while (!stringRedisTemplate.execute(new DefaultRedisScript<>(script, Boolean.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime))) {TimeUnit.MILLISECONDS.sleep(50);}return true;}/***干活的，实现解锁功能*/@Overridepublic void unlock() {String script ="if redis.call('HEXISTS', KEYS[1], ARGV[1]) == 0 then " +"   return nil " +"elseif redis.call('HINCRBY', KEYS[1], ARGV[1], -1) == 0 then " +"   return redis.call('del', KEYS[1]) " +"else " +"   return 0 " +"end";// nil = false 1 = true 0 = falseSystem.out.println("lockName: " + lockName);System.out.println("uuidValue: " + uuidValue);System.out.println("expireTime: " + expireTime);Long flag = stringRedisTemplate.execute(new DefaultRedisScript<>(script,  Long.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime));if(flag == null) {throw new RuntimeException("This lock doesn't EXIST");}}//===下面的redis分布式锁暂时用不到=======================================//===下面的redis分布式锁暂时用不到=======================================//===下面的redis分布式锁暂时用不到=======================================@Overridepublic void lockInterruptibly() throws InterruptedException {}@Overridepublic Condition newCondition() {return null;}}

InventoryServiceImpl直接使用上面的代码设计，有什么问题?

考虑扩展，本次是redis实现分布式锁，以后zookeeper、mysql实现那？？

引入工厂模式改造7.1版code 

DistributedLockFactory

package com.test.redislock.mylock;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;import java.util.concurrent.locks.Lock;/*** @auther admin*/
@Component
public class DistributedLockFactory {@Autowiredprivate StringRedisTemplate stringRedisTemplate;private String lockName;public Lock getDistributedLock(String lockType) {if (lockType == null) {return null;}if (lockType.equalsIgnoreCase("REDIS")) {lockName = "zzyyRedisLock";return new RedisDistributedLock(stringRedisTemplate, lockName);} else if(lockType.equalsIgnoreCase("ZOOKEEPER")){//TODO zookeeper版本的分布式锁实现return new ZookeeperDistributedLock();} else if(lockType.equalsIgnoreCase("MYSQL")){//TODO mysql版本的分布式锁实现return null;}return null;}}

RedisDistributedLock

package com.test.redislock.mylock;import cn.hutool.core.util.IdUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.data.redis.support.collections.DefaultRedisList;
import org.springframework.stereotype.Component;import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;/*** @auther admin*/
//@Component 引入DistributedLockFactory工厂模式，从工厂获得而不再从spring拿到
public class RedisDistributedLock implements Lock {private StringRedisTemplate stringRedisTemplate;//KEYS[1]private String lockName;//ARGV[1]private String uuidValue;//ARGV[2]private long   expireTime;public RedisDistributedLock(StringRedisTemplate stringRedisTemplate, String lockName) {this.stringRedisTemplate = stringRedisTemplate;this.lockName = lockName;//UUID:ThreadIDthis.uuidValue = IdUtil.simpleUUID() + ":"+Thread.currentThread().getId();this.expireTime = 30L;}@Overridepublic void lock(){tryLock();}@Overridepublic boolean tryLock(){try {tryLock(-1L, TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();}return false;}/*** 干活的，实现加锁功能，实现这一个干活的就OK，全盘通用* @param time 过期时间* @param unit 单位* @return 是否获取锁* @throws InterruptedException 异常*/@Overridepublic boolean tryLock(long time, TimeUnit unit) throws InterruptedException {if (time != -1L) {this.expireTime = unit.toSeconds(time);}String script ="if redis.call('exists', KEYS[1]) == 0 or redis.call('hexists', KEYS[1], ARGV[1]) == 1 then " +"redis.call('hincrby', KEYS[1], ARGV[1],1) " +"redis.call('expire', KEYS[1], ARGV[2]) " +"return 1 " +"else " +"return 0 " +"end";System.out.println("script: " + script);System.out.println("lockName: " + lockName);System.out.println("uuidValue: " + uuidValue);System.out.println("expireTime: " + expireTime);while (!stringRedisTemplate.execute(new DefaultRedisScript<>(script, Boolean.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime))) {TimeUnit.MILLISECONDS.sleep(50);}return true;}/***干活的，实现解锁功能*/@Overridepublic void unlock() {String script ="if redis.call('HEXISTS', KEYS[1], ARGV[1]) == 0 then " +"   return nil " +"elseif redis.call('HINCRBY', KEYS[1], ARGV[1], -1) == 0 then " +"   return redis.call('del', KEYS[1]) " +"else " +"   return 0 " +"end";// nil = false 1 = true 0 = falseSystem.out.println("lockName: " + lockName);System.out.println("uuidValue: " + uuidValue);System.out.println("expireTime: " + expireTime);Long flag = stringRedisTemplate.execute(new DefaultRedisScript<>(script, Long.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime));if (flag == null) {throw new RuntimeException("This lock doesn't EXIST");}}//===下面的redis分布式锁暂时用不到=======================================//===下面的redis分布式锁暂时用不到=======================================//===下面的redis分布式锁暂时用不到=======================================@Overridepublic void lockInterruptibly() throws InterruptedException {}@Overridepublic Condition newCondition() {return null;}}

InventoryServiceImpl使用工厂模式版

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import ch.qos.logback.core.joran.conditional.ThenAction;
import cn.hutool.core.util.IdUtil;
import cn.hutool.core.util.StrUtil;
import com.test.redislock.mylock.DistributedLockFactory;
import com.test.redislock.mylock.RedisDistributedLock;
import lombok.extern.slf4j.Slf4j;
import org.omg.IOP.TAG_RMI_CUSTOM_MAX_STREAM_FORMAT;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.stereotype.Service;import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;@Autowiredprivate DistributedLockFactory distributedLockFactory;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";Lock redisLock = distributedLockFactory.getDistributedLock("redis");redisLock.lock();try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {inventoryNumber = inventoryNumber - 1;stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber + "\t服务端口:" + port;System.out.println(retMessage);return retMessage;}retMessage = "商品卖完了，o(╥﹏╥)o" + "\t服务端口:"  + port;} catch (Exception e) {e.printStackTrace();} finally {redisLock.unlock();}return retMessage;}}

单机+并发测试通过

http://localhost:7777/inventory/sale

可重入性测试重点

可重入测试？？？

InventoryServiceImpl类新增可重入测试方法

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import com.test.redislock.mylock.DistributedLockFactory;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;import javax.annotation.Resource;
import java.util.concurrent.locks.Lock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;@Autowiredprivate DistributedLockFactory distributedLockFactory;/*** 模拟商品库存扣减*/@Overridepublic String sale() {String retMessage = "";Lock redisLock = distributedLockFactory.getDistributedLock("redis");redisLock.lock();try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber + "\t";System.out.println(retMessage);testReEnter();} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} catch (Exception e) {e.printStackTrace();} finally {redisLock.unlock();}return retMessage + "\t" + "服务端口号：" + port;}/*** 可重入性测试方法*/private void testReEnter() {Lock redisLock = distributedLockFactory.getDistributedLock("redis");redisLock.lock();try {System.out.println("################测试可重入锁#######");} finally {redisLock.unlock();}}}

http://localhost:7777/inventory/sale

结果

ThreadID一致了但是UUID不OK，o(╥﹏╥)o

引入工厂模式改造7.2版code

DistributedLockFactory

package com.test.redislock.mylock;import cn.hutool.core.util.IdUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;import java.util.concurrent.locks.Lock;/*** @auther admin*/
@Component
public class DistributedLockFactory {@Autowiredprivate StringRedisTemplate stringRedisTemplate;private String lockName;private String uuidValue;public DistributedLockFactory() {//UUIDthis.uuidValue = IdUtil.simpleUUID();}public Lock getDistributedLock(String lockType) {if (lockType == null) {return null;} if (lockType.equalsIgnoreCase("REDIS")) {lockName = "zzyyRedisLock";return new RedisDistributedLock(stringRedisTemplate, lockName, uuidValue);} else if(lockType.equalsIgnoreCase("ZOOKEEPER")) {//TODO zookeeper版本的分布式锁实现return new ZookeeperDistributedLock();} else if(lockType.equalsIgnoreCase("MYSQL")) {//TODO mysql版本的分布式锁实现return null;}return null;}
}

RedisDistributedLock

package com.test.redislock.mylock;import cn.hutool.core.util.IdUtil;
import lombok.SneakyThrows;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;import java.util.Arrays;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;/*** @auther admin*/
public class RedisDistributedLock implements Lock {private StringRedisTemplate stringRedisTemplate;private String lockName;private String uuidValue;private long expireTime;public RedisDistributedLock(StringRedisTemplate stringRedisTemplate, String lockName, String uuidValue) {this.stringRedisTemplate = stringRedisTemplate;this.lockName = lockName;this.uuidValue = uuidValue + ":" + Thread.currentThread().getId();this.expireTime = 30L;}@Overridepublic void lock() {this.tryLock();}@Overridepublic boolean tryLock() {try {return this.tryLock(-1L, TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();}return false;}@Overridepublic boolean tryLock(long time, TimeUnit unit) throws InterruptedException {if(time != -1L) {expireTime = unit.toSeconds(time);}String script ="if redis.call('exists', KEYS[1]) == 0 or redis.call('hexists', KEYS[1], ARGV[1]) == 1 then " +"redis.call('hincrby', KEYS[1], ARGV[1], 1) " +"redis.call('expire', KEYS[1], ARGV[2]) " +"return 1 " +"else " +"return 0 " +"end";System.out.println("lockName: " + lockName + "\t" + "uuidValue: " + uuidValue);while (!stringRedisTemplate.execute(new DefaultRedisScript<>(script, Boolean.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime))){try { TimeUnit.MILLISECONDS.sleep(60); } catch (InterruptedException e) {e.printStackTrace();}}return true;}@Overridepublic void unlock() {String script ="if redis.call('HEXISTS', KEYS[1], ARGV[1]) == 0 then " +"return nil " +"elseif redis.call('HINCRBY', KEYS[1], ARGV[1],-1) == 0 then " +"return redis.call('del', KEYS[1]) " +"else " +"return 0 " +"end";System.out.println("lockName: " + lockName + "\t" + "uuidValue: " + uuidValue);Long flag = stringRedisTemplate.execute(new DefaultRedisScript<>(script, Long.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime));if(flag == null) {throw new RuntimeException("没有这个锁，HEXISTS查询无");}}//=========================================================@Overridepublic void lockInterruptibly() throws InterruptedException {}@Overridepublic Condition newCondition() {return null;}}

InventoryServiceImpl类新增可重入测试方法

package com.test.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import com.test.redislock.mylock.DistributedLockFactory;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.stereotype.Service;import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;@Autowiredprivate DistributedLockFactory distributedLockFactory;/*** 模拟商品库存扣减*/public String sale() {String retMessage = "";Lock redisLock = distributedLockFactory.getDistributedLock("redis");redisLock.lock();try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);this.testReEnter();} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} catch (Exception e) {e.printStackTrace();} finally {redisLock.unlock();}return retMessage + "\t" + "服务端口号：" + port;}/*** 可重入性测试方法*/private void testReEnter() {Lock redisLock = distributedLockFactory.getDistributedLock("redis");redisLock.lock();try {System.out.println("################测试可重入锁####################################");} finally {redisLock.unlock();}}}

单机+并发+可重入性，测试通过

8.自动续期

确保redisLock过期时间大于业务执行时间的问题。

分布式锁如何续期？

CAP

Redis集群是AP（AP）

redis异步复制造成的锁丢失，比如：主节点没来的及把刚刚set进来这条数据给从节点，master就挂了，从机上位但从机上无该数据。

Zookeeper集群是CP（CP）

故障

顺便复习Eureka集群是AP（AP）

顺便复习Nacos集群是AP

加个钟，lua脚本

hset zzyyRedisLock 111122223333:11 3

EXPIRE zzyyRedisLock 30

ttl zzyyRedisLock

。。。。。

eval "if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 1 then return redis.call('expire',KEYS[1],ARGV[2]) else return 0 end" 1 zzyyRedisLock 111122223333:11 30

ttl zzyyRedisLock

//==============自动续期 if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 1 then return redis.call('expire',KEYS[1],ARGV[2]) else return 0 end

8.0版新增自动续期功能

修改为V8.0版程序

del掉之前的lockName    zzyyRedisLock

RedisDistributedLock

package com.test.redislock.mylock;import cn.hutool.core.util.IdUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.data.redis.support.collections.DefaultRedisList;
import org.springframework.stereotype.Component;import java.util.Arrays;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;/*** @auther admin*/
public class RedisDistributedLock implements Lock {private StringRedisTemplate stringRedisTemplate;//KEYS[1]private String lockName;//ARGV[1]private String uuidValue;//ARGV[2]private long   expireTime;public RedisDistributedLock(StringRedisTemplate stringRedisTemplate, String lockName,String uuidValue) {this.stringRedisTemplate = stringRedisTemplate;this.lockName = lockName;this.uuidValue = uuidValue + ":" + Thread.currentThread().getId();this.expireTime = 30L;}@Overridepublic void lock() {tryLock();}@Overridepublic boolean tryLock() {try {tryLock(-1L, TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();}return false;}/*** 干活的，实现加锁功能，实现这一个干活的就OK，全盘通用* @param time 尝试时间* @param unit 单位* @return 是否加锁成功* @throws InterruptedException 异常*/@Overridepublic boolean tryLock(long time, TimeUnit unit) throws InterruptedException {if(time != -1L) {this.expireTime = unit.toSeconds(time);}String script ="if redis.call('exists', KEYS[1]) == 0 or redis.call('hexists', KEYS[1], ARGV[1]) == 1 then " +"redis.call('hincrby', KEYS[1], ARGV[1],1) " +"redis.call('expire', KEYS[1], ARGV[2]) " +"return 1 " +"else " +"return 0 " +"end";System.out.println("script: " + script);System.out.println("lockName: " + lockName);System.out.println("uuidValue: " + uuidValue);System.out.println("expireTime: " + expireTime);while (!stringRedisTemplate.execute(new DefaultRedisScript<>(script, Boolean.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime))) {TimeUnit.MILLISECONDS.sleep(50);}this.renewExpire();return true;}/***干活的，实现解锁功能*/@Overridepublic void unlock() {String script ="if redis.call('HEXISTS', KEYS[1], ARGV[1]) == 0 then " +"   return nil " +"elseif redis.call('HINCRBY', KEYS[1], ARGV[1],-1) == 0 then " +"   return redis.call('del', KEYS[1]) " +"else " +"   return 0 " +"end";// nil = false 1 = true 0 = falseSystem.out.println("lockName: " + lockName);System.out.println("uuidValue: " + uuidValue);System.out.println("expireTime: " + expireTime);Long flag = stringRedisTemplate.execute(new DefaultRedisScript<>(script, Long.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime));if(flag == null) {throw new RuntimeException("This lock doesn't EXIST");}}/*** 锁自动续期*/private void renewExpire() {String script ="if redis.call('HEXISTS', KEYS[1], ARGV[1]) == 1 then " +"return redis.call('expire', KEYS[1], ARGV[2]) " +"else " +"return 0 " +"end";new Timer().schedule(new TimerTask() {@Overridepublic void run() {if (stringRedisTemplate.execute(new DefaultRedisScript<>(script, Boolean.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime))) {renewExpire();}}}, (this.expireTime * 1000) / 3);}//===下面的redis分布式锁暂时用不到=======================================//===下面的redis分布式锁暂时用不到=======================================//===下面的redis分布式锁暂时用不到=======================================@Overridepublic void lockInterruptibly() throws InterruptedException {}@Overridepublic Condition newCondition() {return null;}}

InventoryServiceImpl

package com.atguigu.redislock.service.impl;import com.test.redislock.service.InventoryService;import cn.hutool.core.util.IdUtil;
import com.atguigu.redislock.mylock.DistributedLockFactory;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.stereotype.Service;import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;/*** @auther admin*/
@Slf4j
@Service
public class InventoryServiceImpl implements InventoryService {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@Value("${server.port}")private String port;@Autowiredprivate DistributedLockFactory distributedLockFactory;/*** 模拟商品库存扣减*/public String sale() {String retMessage = "";Lock redisLock = distributedLockFactory.getDistributedLock("redis");redisLock.lock();try {//1 查询库存信息String result = stringRedisTemplate.opsForValue().get("inventory001");//2 判断库存是否足够Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);//3 扣减库存if (inventoryNumber > 0) {stringRedisTemplate.opsForValue().set("inventory001", String.valueOf(--inventoryNumber));retMessage = "成功卖出一个商品，库存剩余: " + inventoryNumber;System.out.println(retMessage);//暂停几秒钟线程,为了测试自动续期try { TimeUnit.SECONDS.sleep(120);} catch (InterruptedException e) {e.printStackTrace();}} else {retMessage = "商品卖完了，o(╥﹏╥)o";}} catch (Exception e) {e.printStackTrace();} finally {redisLock.unlock();}return retMessage + "\t" + "服务端口号：" + port;}/*** 可重入性测试方法*/private void testReEnter() {Lock redisLock = distributedLockFactory.getDistributedLock("redis");redisLock.lock();try {System.out.println("################测试可重入锁####################################");} finally {redisLock.unlock();}}}

记得去掉可重入测试testReEnter()

InventoryService业务逻辑里面故意sleep一段时间测试自动续期

总结

synchronized单机版OK，上分布式出现异常。

nginx分布式微服务单机锁不行/(ㄒoㄒ)/~~。

取消单机锁，上redis分布式锁setnx。

只加了锁，没有释放锁，出异常的话，可能无法释放锁，必须要在代码层面finally释放锁。

宕机了，部署了微服务代码层面根本没有走到finally这块，没办法保证解锁，这个key没有被删除，需要有lockKey的过期时间设定。

为redis的分布式锁key，增加过期时间此外，还必须要setnx+过期时间必须同一行。

必须规定只能自己删除自己的锁，你不能把别人的锁删除了,防止张冠李戴，1删2,2删3。

unlock变为Lua脚本保证。

锁重入，hset替代setnx+lock变为Lua脚本保证。

自动续期。

面试题总结

Redis除了拿来做缓存，你还见过基于Redis的什么用法？

• 数据共享，分布式Session
• 分布式锁
• 全局ID
• 计算器、点赞
• 位统计
• 购物车
• 轻量级消息队列（list、stream）
• 抽奖
• 点赞、签到、打卡
• 差集交集并集，用户关注、可能认识的人，推荐模型
• 热点新闻、热搜排行榜

Redis 做分布式锁的时候有需要注意的问题？

你们公司自己实现的分布式锁是否用的setnx命令实现？这个是最合适的吗？你如何考虑分布式锁的可重入问题？

如果是 Redis 是单点部署的，会带来什么问题？那你准备怎么解决单点问题呢？

Redis集群模式下，比如主从模式，CAP方面有没有什么问题呢？

那你简单的介绍一下 Redlock 吧？你简历上写redisson，你谈谈。

Redis分布式锁如何续期？看门狗知道吗？

。。。。。。