redis是线程安全的，天然具有线程安全的特性，支持原子性操作，限流服务不仅需要承接超高QPS，还要保证限流逻辑的执行层面具备线程安全的特性，利用Redis这些特性做限流，既能保证线程安全，也能保证性能。
结合上面的流程图，这里梳理出一个整体的实现思路：
编写lua脚本，指定入参的限流规则，比如对特定的接口限流时，可以根据某个或几个参数进行判定，调用该接口的请求，在一定的时间窗口内监控请求次数；
既然是限流，最好能够通用，可将限流规则应用到任何接口上，那么最合适的方式就是通过自定义注解形式切入；
引入redis依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
自定义注解
@Target({ElementType.METHOD, ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Inherited @Documented public @interface RedisLimitAnnotation { /** * key */ String key() default ""; /** * Key的前缀 */ String prefix() default ""; /** * 一定时间内最多访问次数 */ int count(); /** * 给定的时间范围 单位(秒) */ int period(); /** * 限流的类型(用户自定义key或者请求ip) */ LimitType limitType() default LimitType.CUSTOMER; }
自定义redis配置类
import org.springframework.context.annotation.Bean; import org.springframework.core.io.ClassPathResource; import org.springframework.data.redis.connection.RedisConnectionFactory; import org.springframework.data.redis.core.RedisTemplate; import org.springframework.data.redis.core.script.DefaultRedisScript; import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer; import org.springframework.data.redis.serializer.StringRedisSerializer; import org.springframework.scripting.support.ResourceScriptSource; import org.springframework.stereotype.Component; import java.io.Serializable; @Component public class RedisConfiguration { @Bean public DefaultRedisScript<Number> redisluaScript() { DefaultRedisScript<Number> redisScript = new DefaultRedisScript<>(); redisScript.setScriptSource(new ResourceScriptSource(new ClassPathResource("limit.lua"))); redisScript.setResultType(Number.class); return redisScript; } @Bean("redisTemplate") public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory) { RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>(); redisTemplate.setConnectionFactory(redisConnectionFactory); Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class); //设置value的序列化方式为JSOn redisTemplate.setValueSerializer(jackson2JsonRedisSerializer); //设置key的序列化方式为String redisTemplate.setKeySerializer(new StringRedisSerializer()); redisTemplate.setHashKeySerializer(new StringRedisSerializer()); redisTemplate.setHashValueSerializer(jackson2JsonRedisSerializer); redisTemplate.afterPropertiesSet(); return redisTemplate; } }
自定义限流AOP类
import org.aspectj.lang.ProceedingJoinPoint; import org.aspectj.lang.annotation.Around; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Pointcut; 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.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; import java.util.Collections; import java.util.List; @Aspect @Configuration public class LimitRestAspect { private static final Logger logger = LoggerFactory.getLogger(LimitRestAspect.class); @Autowired private RedisTemplate<String, Object> redisTemplate; @Autowired private DefaultRedisScript<Number> redisluaScript; @Pointcut(value = "@annotation(com.congge.config.limit.RedisLimitAnnotation)") public void rateLimit() { } @Around("rateLimit()") public Object interceptor(ProceedingJoinPoint joinPoint) throws Throwable { MethodSignature signature = (MethodSignature) joinPoint.getSignature(); Method method = signature.getMethod(); Class<?> targetClass = method.getDeclaringClass(); RedisLimitAnnotation rateLimit = method.getAnnotation(RedisLimitAnnotation.class); if (rateLimit != null) { HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest(); String ipAddress = getIpAddr(request); StringBuffer stringBuffer = new StringBuffer(); stringBuffer.append(ipAddress).append("-") .append(targetClass.getName()).append("- ") .append(method.getName()).append("-") .append(rateLimit.key()); List<String> keys = Collections.singletonList(stringBuffer.toString()); //调用lua脚本，获取返回结果，这里即为请求的次数 Number number = redisTemplate.execute( redisluaScript, keys, rateLimit.count(), rateLimit.period() ); if (number != null && number.intValue() != 0 && number.intValue() <= rateLimit.count()) { logger.info("限流时间段内访问了第：{} 次", number.toString()); return joinPoint.proceed(); } } else { return joinPoint.proceed(); } throw new RuntimeException("访问频率过快，被限流了"); } /** * 获取请求的IP方法 * @param request * @return */ private static String getIpAddr(HttpServletRequest request) { String ipAddress = null; try { ipAddress = request.getHeader("x-forwarded-for"); if (ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) { ipAddress = request.getHeader("Proxy-Client-IP"); } if (ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) { ipAddress = request.getHeader("WL-Proxy-Client-IP"); } if (ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) { ipAddress = request.getRemoteAddr(); } // 对于通过多个代理的情况，第一个IP为客户端真实IP,多个IP按照','分割 if (ipAddress != null && ipAddress.length() > 15) { if (ipAddress.indexOf(",") > 0) { ipAddress = ipAddress.substring(0, ipAddress.indexOf(",")); } } } catch (Exception e) { ipAddress = ""; } return ipAddress; } }
该类要做的事情和上面的两种限流措施类似，不过在这里核心的限流是通过读取lua脚步，通过参数传递给lua脚步实现的。
自定义lua脚本
在工程的resources目录下，添加如下的lua脚本
local key = "rate.limit:" .. KEYS[1] local limit = tonumber(ARGV[1]) local current = tonumber(redis.call('get', key) or "0") if current + 1 > limit then return 0 else -- 没有超阈值，将当前访问数量+1，并设置2秒过期（可根据自己的业务情况调整） redis.call("INCRBY", key,"1") redis.call("expire", key,"2") return current + 1 end
添加测试接口
@RestController public class RedisController { //localhost:8081/redis/limit @GetMapping("/redis/limit") @RedisLimitAnnotation(key = "queryFromRedis",period = 1, count = 1) public String queryFromRedis(){ return "success"; } }