Redis + Lua 实现分布式限流器

相比 Redis事务， Lua脚本的优点：

• 减少网络开销：使用Lua脚本，无需向Redis 发送多次请求，执行一次即可，减少网络传输
• 原子操作：Redis 将整个Lua脚本作为一个命令执行，原子，无需担心并发
• 复用：Lua脚本一旦执行，会永久保存 Redis 中,，其他客户端可复用

Redis + Lua 限流实现

技术栈：自定义注解、aop、Redis + Lua 实现限流

1. 导入依赖

 <dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-aop</artifactId></dependency><dependency><groupId>org.apache.commons</groupId><artifactId>commons-lang3</artifactId></dependency><dependency><groupId>com.google.guava</groupId><artifactId>guava</artifactId><version>30.1-jre</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies>

2. 配置application.properties

spring.redis.host=10.1.61.121
spring.redis.port=6379
spring.redis.password=123456

3. 配置RedisTemplate实例

package com.lihw.lihwtestboot.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;
import java.io.Serializable;@Configuration
public class RedisLimiterHelper {@Beanpublic RedisTemplate<String, Serializable> limitRedisTemplate(LettuceConnectionFactory redisConnectionFactory) {RedisTemplate<String, Serializable> template = new RedisTemplate<>();template.setKeySerializer(new StringRedisSerializer());template.setValueSerializer(new GenericJackson2JsonRedisSerializer());template.setConnectionFactory(redisConnectionFactory);return template;}
}

4. 定义限流类型枚举类

package com.lihw.lihwtestboot.schemas;/*** @explain: 限流类型* @author: lihewei
*/
public enum LimitType {/*** 自定义key*/CUSTOMER,/*** 请求者IP*/IP;
}

5. 自定义注解

• period表示请求限制时间段
• count表示在period这个时间段内允许放行请求的次数。
• limitType代表限流的类型，可以根据请求的IP、自定义key，如果不传limitType属性则默认用方法名作为默认key。

package com.lihw.lihwtestboot.anno;
import com.lihw.lihwtestboot.schemas.LimitType;
import java.lang.annotation.*;/*** @explain: 自定义限流注解* @author: lihewei
*/
@Target({ElementType.METHOD, ElementType.TYPE})//作用于方法上
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface Limit {/*** 名字*/String name() default "";/*** key*/String key() default "";/*** Key的前缀*/String prefix() default "";/*** 给定的时间范围 单位(秒)*/int period();/*** 一定时间内最多访问次数*/int count();/*** 限流的类型(用户自定义key 或者 请求ip)*/LimitType limitType() default LimitType.CUSTOMER;
}

6. 切面代码实现

package com.lihw.lihwtestboot.aop;
import com.google.common.collect.ImmutableList;
import com.lihw.lihwtestboot.anno.Limit;
import com.lihw.lihwtestboot.schemas.LimitType;
import org.apache.commons.lang3.StringUtils;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.reflect.MethodSignature;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.data.redis.core.script.RedisScript;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.HttpServletRequest;
import java.io.Serializable;
import java.lang.reflect.Method;/*** @explain: 限流切面实现* @author: lihewei
*/
@Aspect
@Configuration
public class LimitInterceptor {private static final Logger logger = LoggerFactory.getLogger(LimitInterceptor.class);private static final String UNKNOWN = "unknown";private final RedisTemplate<String, Serializable> limitRedisTemplate;@Autowiredpublic LimitInterceptor(RedisTemplate<String, Serializable> limitRedisTemplate) {this.limitRedisTemplate = limitRedisTemplate;}/*** @author lihw* @description 切面*/@Around("execution(public * *(..)) && @annotation(com.lihw.lihwtestboot.anno.Limit)")public Object interceptor(ProceedingJoinPoint pjp) {MethodSignature signature = (MethodSignature) pjp.getSignature();Method method = signature.getMethod();Limit limitAnnotation = method.getAnnotation(Limit.class);LimitType limitType = limitAnnotation.limitType();String name = limitAnnotation.name();String key;int limitPeriod = limitAnnotation.period();int limitCount = limitAnnotation.count();/*** 根据限流类型获取不同的key ,如果不传我们会以方法名作为key*/switch (limitType) {case IP:key = getIpAddress();break;case CUSTOMER:key = limitAnnotation.key();break;default:key = StringUtils.upperCase(method.getName());}ImmutableList<String> keys = ImmutableList.of(StringUtils.join(limitAnnotation.prefix(), key));try {String luaScript = buildLuaScript();RedisScript<Number> redisScript = new DefaultRedisScript<>(luaScript, Number.class);Number count = limitRedisTemplate.execute(redisScript, keys, limitCount, limitPeriod);logger.info("Access try count is {} for name={} and key = {}", count, name, key);if (count != null && count.intValue() <= limitCount) {return pjp.proceed();} else {throw new RuntimeException("You have been dragged into the blacklist");}} catch (Throwable e) {if (e instanceof RuntimeException) {throw new RuntimeException(e.getLocalizedMessage());}throw new RuntimeException("server exception");}}/*** @description 编写 redis Lua 限流脚本*/public String buildLuaScript() {StringBuilder lua = new StringBuilder();lua.append("local c");lua.append("\nc = redis.call('get',KEYS[1])");// 调用不超过最大值，则直接返回lua.append("\nif c and tonumber(c) > tonumber(ARGV[1]) then");lua.append("\nreturn c;");lua.append("\nend");// 执行计算器自加lua.append("\nc = redis.call('incr',KEYS[1])");lua.append("\nif tonumber(c) == 1 then");// 从第一次调用开始限流，设置对应键值的过期lua.append("\nredis.call('expire',KEYS[1],ARGV[2])");lua.append("\nend");lua.append("\nreturn c;");return lua.toString();}/*** @description 获取id地址*/public String getIpAddress() {HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();String ip = request.getHeader("x-forwarded-for");if (ip == null || ip.length() == 0 || UNKNOWN.equalsIgnoreCase(ip)) {ip = request.getHeader("Proxy-Client-IP");}if (ip == null || ip.length() == 0 || UNKNOWN.equalsIgnoreCase(ip)) {ip = request.getHeader("WL-Proxy-Client-IP");}if (ip == null || ip.length() == 0 || UNKNOWN.equalsIgnoreCase(ip)) {ip = request.getRemoteAddr();}return ip;}
}

7. 控制层实现

package com.lihw.lihwtestboot.controller;import com.lihw.lihwtestboot.anno.Limit;
import com.lihw.lihwtestboot.schemas.LimitType;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.concurrent.atomic.AtomicInteger;@RestController
public class LimiterController {private static final AtomicInteger ATOMIC_INTEGER_1 = new AtomicInteger();private static final AtomicInteger ATOMIC_INTEGER_2 = new AtomicInteger();private static final AtomicInteger ATOMIC_INTEGER_3 = new AtomicInteger();@Limit(key = "limitTest", period = 10, count = 3)@GetMapping("/limitTest1")public int testLimiter1() {return ATOMIC_INTEGER_1.incrementAndGet();}@Limit(key = "customer_limit_test", period = 10, count = 3, limitType = LimitType.CUSTOMER)@GetMapping("/limitTest2")public int testLimiter2() {return ATOMIC_INTEGER_2.incrementAndGet();}@Limit(key = "ip_limit_test", period = 10, count = 3, limitType = LimitType.IP)@GetMapping("/limitTest3")public int testLimiter3() {return ATOMIC_INTEGER_3.incrementAndGet();}
}

8. 测试

10s内连续请求三次以上拒绝请求