文章引用:https://mp.weixin.qq.com/s/XgdKE2rBKL0-nFk2NJPuyg
一、单个服务
1.代码
该接口的作用是累加一个值,访问一次该值加1
@RestController
public class LockController {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@GetMapping("/increment")public String increment() {int counter = Integer.parseInt(stringRedisTemplate.opsForValue().get("count"));counter++;System.out.println("当前结果:" + counter);stringRedisTemplate.opsForValue().set("count", String.valueOf(counter));return "结果:" + counter;}
}
2.jmeter工具压测
用100个线程,每个线程访问100次去压测,理论上该值最后应该返回10000
3.结果
发生了线程安全问题,部分请求返回结果相同
4.解决办法:加锁
@RestController
public class LockController {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@GetMapping("/increment")public synchronized String increment() {int counter = Integer.parseInt(stringRedisTemplate.opsForValue().get("count"));counter++;System.out.println("当前结果:" + counter);stringRedisTemplate.opsForValue().set("count", String.valueOf(counter));return "结果:" + counter;}
}
在非集群模式下,简单上锁能解决线程安全问题。
二、集群模式
代码相同,idea启动两个相同的服务
1.启动两个服务
2.nginx配置负载均衡
upstream backend {# 定义后端服务器列表server localhost:8081;server localhost:8082;}server {listen 8080;location / {# 将请求代理到后端服务器proxy_pass http://backend;}}
3.jmeter工具压测
用100个线程,每个线程访问100次去压测,理论上该值最后应该返回10000
还是出了线程安全问题,synchronized只能锁住单个服务
三、SpringBoot整合Redisson(注解方式)
1.依赖和配置文件
<dependencies><!-- Spring Boot Starter for Web --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- Redisson Dependency--><dependency><groupId>org.redisson</groupId><artifactId>redisson-spring-boot-starter</artifactId><version>3.17.6</version><!-- 请根据需要调整版本 --></dependency><dependency><groupId>org.aspectj</groupId><artifactId>aspectjweaver</artifactId><version>1.8.10</version></dependency></dependencies>
spring:
redis:host:localhostport:6379# Redisson configuration
redisson:single-server-address:redis://@localhost:6379
2.代码
注解
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DistributedLock {String lockName();
}
切面
@Aspect
@Component
public class DistributedLockAspect {@Autowiredprivate RedissonClient redissonClient;@Around("@annotation(DistributedLock)")public Object around(ProceedingJoinPoint joinPoint) throws Throwable {MethodSignature signature = (MethodSignature) joinPoint.getSignature();DistributedLock annotation = signature.getMethod().getAnnotation(DistributedLock.class);String lockName = annotation.lockName();RLock lock = redissonClient.getLock(lockName);try {// 尝试获取锁,最多等待10秒,持有锁的时间为30秒if (!lock.tryLock(10, 30, TimeUnit.SECONDS)) {throw new RuntimeException("Failed to acquire lock.");}return joinPoint.proceed();} finally {// 确保在任何情况下都能释放锁if (lock.isHeldByCurrentThread()) {lock.unlock();}}}
}
接口
@RestController
public class LockController {@Autowiredprivate StringRedisTemplate stringRedisTemplate;@GetMapping("/increment")@DistributedLock(lockName = "counterLock")public String increment() {int counter = Integer.parseInt(stringRedisTemplate.opsForValue().get("count"));counter++;System.out.println("当前结果:" + counter);stringRedisTemplate.opsForValue().set("count", String.valueOf(counter));return "结果:" + counter;}
}
3.结果
实现了分布式锁,俩个服务依次接受了所有请求,并无重复值