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SpringCloud AlibabaSentinel实现熔断与限流(1)


初始化演示工程

前提启动nacos,Sentinel成功

新建cloudalibaba-sentinel-service8401

pom文件

<?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">
<parent>
<artifactId>cloud2020</artifactId>
<groupId>com.atguigu.springcloud</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>

<artifactId>cloudalibaba-sentinel-service8401</artifactId>

<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
</properties>
<dependencies>
<!--SpringCloud ailibaba nacos -->
<dependency>
<groupId>com.alibaba.cloud</groupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>

<!--SpringCloud ailibaba sentinel -->
<dependency>
<groupId>com.alibaba.cloud</groupId>
<artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>

yml文件

rver:
port: 8401

spring:
application:
name: cloudalibaba-sentinel-service
cloud:
nacos:
discovery:
#Nacos服务注册中心地址
server-addr: localhost:8848
sentinel:
transport:
#配置Sentinel dashboard地址
dashboard: localhost:8080
#默认8719端口,假如被占用会自动从8719开始依次+1扫描,直至找到未被占用的端口
port: 8719

management:
endpoints:
web:
exposure:
include: '*'
sentinel:
enabled: true

主启动类

@EnableDiscoveryClient
@SpringBootApplication
public class MainApp8401
{
public static void main(String[] args) {
SpringApplication.run(MainApp8401.class, args);
}
}

业务类

@RestController
public class FlowLimitController
{

@GetMapping("/testA")
public String testA()
{
return "------testA";
}

@GetMapping("/testB")
public String testB()
{
return "------testB";
}
}

 测试1

访问​​http://localhost:8401/testA​​

SpringCloud AlibabaSentinel实现熔断与限流(1)_xml


 访问​​http://localhost:8401/testB​​

SpringCloud AlibabaSentinel实现熔断与限流(1)_xml_02

 访问​​http://localhost:8080​​

SpringCloud AlibabaSentinel实现熔断与限流(1)_spring_03


 流控规则

基本介绍

SpringCloud AlibabaSentinel实现熔断与限流(1)_spring_04

SpringCloud AlibabaSentinel实现熔断与限流(1)_java_05

流控模式 

直接(默认)

直接->快速失败

配置及说明

表示1秒钟内查询1次就是OK,若超过次数1,就直接-快速失败,报默认错误

SpringCloud AlibabaSentinel实现熔断与限流(1)_java_06

 测试2

快速点击访问http://localhost:8401/testA

SpringCloud AlibabaSentinel实现熔断与限流(1)_spring_07


关联

设置效果
当关联资源/testB的qps阀值超过1时,就限流/testA的Rest访问地址,当关联资源到阈值后限制配置好的资源名

SpringCloud AlibabaSentinel实现熔断与限流(1)_spring_08

测试3

postman发送请求​​http://localhost:8401/testB​​

SpringCloud AlibabaSentinel实现熔断与限流(1)_xml_09


链路

多个请求调用了同一个微服务

流控效果

直接->快速失败(默认的流控处理)

直接失败,抛出异常

Blocked by Sentinel (flow limiting)

源码

com.alibaba.csp.sentinel.slots.block.flow.controller.DefaultController

预热 

说明:公式:阈值除以coldFactor(默认值为3),经过预热时长后才会达到阈值

官网

SpringCloud AlibabaSentinel实现熔断与限流(1)_spring_13

默认coldFactor为3,即请求 QPS 从 threshold / 3 开始,经预热时长逐渐升至设定的 QPS 阈值。 


SpringCloud AlibabaSentinel实现熔断与限流(1)_spring_14

默认 coldFactor 为 3,即请求QPS从(threshold / 3) 开始,经多少预热时长才逐渐升至设定的 QPS 阈值。 

测试4

应用场景
如:秒杀系统在开启的瞬间,会有很多流量上来,很有可能把系统打死,预热方式就是把为了保护系统,可慢慢的把流量放进来,慢慢的把阀值增长到设置的阀值。 

排队等待

匀速排队,让请求以均匀的速度通过,阀值类型必须设成QPS,否则无效。

设置含义:/testA每秒1次请求,超过的话就排队等待,等待的超时时间为20000毫秒。

SpringCloud AlibabaSentinel实现熔断与限流(1)_maven_16

官网 

https://github.com/alibaba/Sentinel/wiki/%E6%B5%81%E9%87%8F%E6%8E%A7%E5%88%B6

SpringCloud AlibabaSentinel实现熔断与限流(1)_spring cloud_17

 

 

源码 

com.alibaba.csp.sentinel.slots.block.flow.controller.RateLimiterController

SpringCloud AlibabaSentinel实现熔断与限流(1)_maven_18

 

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