SpringCloud11-Alibaba_Sentinel（熔断与限流）
1、Sentinel介绍
（1）Hystrix缺点：
- 需要手工搭建监控平台；
- 没有界面监控细粒度化的配置；
- Sentinel是一个可以独立出来的单独组件，界面化统一配置；
（2）作用：
- 从流量监控、熔断降级、负载均衡保护等多个维度保护服务的稳定性；
（3）特性
- 丰富的应用场景：秒杀、削峰、熔断等多场景使用；
- 完备的实时监控：实时监控；
- 广泛的开源生态：开箱即用，快速整合；
- 完善的SPI扩展点：快速扩展定制逻辑；
2、下载安装
- 注意8080端口不要被占用
（1）下载：https://github.com/alibaba/Sentinel/releases
（2）接下来步骤查看：https://blog.csdn.net/weixin_45176509/article/details/123583281
3、使用
- pom.xml
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-sentinelartifactId>
<version>0.9.0.RELEASEversion>
dependency>
<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>cloud2022artifactId>
<groupId>org.examplegroupId>
<version>1.0-SNAPSHOTversion>
parent>
<modelVersion>4.0.0modelVersion>
<groupId>org.consumer8083groupId>
<artifactId>cloud-alibaba-consumer8083artifactId>
<dependencies>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-sentinelartifactId>
<version>0.9.0.RELEASEversion>
dependency>
<dependency>
<groupId>com.alibaba.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-nacos-configartifactId>
<version>2.2.7.RELEASEversion>
dependency>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
<version>0.9.0.RELEASEversion>
dependency>
<dependency>
<groupId>com.commonsgroupId>
<artifactId>commonsartifactId>
<version>1.0-SNAPSHOTversion>
<scope>compilescope>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-webartifactId>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-actuatorartifactId>
dependency>
<dependency>
<groupId>com.baomidougroupId>
<artifactId>mybatis-plus-boot-starterartifactId>
dependency>
<dependency>
<groupId>com.alibabagroupId>
<artifactId>druid-spring-boot-starterartifactId>
<version>1.1.10version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-jdbcartifactId>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-devtoolsartifactId>
<scope>runtimescope>
<optional>trueoptional>
dependency>
<dependency>
<groupId>org.projectlombokgroupId>
<artifactId>lombokartifactId>
<optional>trueoptional>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-testartifactId>
<scope>testscope>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-devtoolsartifactId>
<scope>runtimescope>
<optional>trueoptional>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-autoconfigureartifactId>
dependency>
dependencies>
project>
- application.yml
server:
port: 8083
spring:
application:
name: consumer-nacos
cloud:
nacos:
discovery:
server-addr: 127.0.0.1:8848
config:
server-addr: localhost:8848
file-extension: yaml
sentinel: #配置
transport:
dashboard: localhost:8080
port: 8719 #默认为8719，如果占用会从8719+1开始扫描寻找未占用端口
management: #暴露监控
endpoints:
web:
exposure.include: '*'
- 主启动
package com.consumer;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
@SpringBootApplication
@EnableDiscoveryClient
public class NacosConsumerDemoApplication {
public static void main(String[] args) {
SpringApplication.run(NacosConsumerDemoApplication.class, args);
}
}
- 业务Controller：未作变化，与Nacos相同
package com.consumer.Controller;
import com.commons.Entity.Result;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import javax.annotation.Resource;
@RestController
@RequestMapping("nacos/")
@RefreshScope //动态刷新
public class ConsumerController {
@Resource
private RestTemplate restTemplate;
@Value("${spring.datasource.username}")
private String configInfo;
@Value("${service-url.nacos-user-service}")
private String url;
@GetMapping("/{id}")
public Result saveEntity(@PathVariable("id") Integer id) {
return restTemplate.getForObject(url+"/nacos/"+id,Result.class);
}
@GetMapping("/getInfo")
public String getInfo() {
return configInfo;
}
}
- 启动项目，首次访问sentinel空空如也，他是懒加载机制，要访问接口之后才会加载，访问Controller接口，再次访问，效果如下：
4、规则
（1）簇点链路
（2）流控规则
配置说明：
- 阈值类型
配置QPS快速失败：
QPS：御敌于国门之外；
线程数：关门打狗； - 流控模式
直接：默认模式；
关联：当与自己关联的资源达到阈值后就限流自己；
链路：多个请求操作同一个微服务
- 流控效果
快速失败：默认处理;
WarmUp（预热）：长期处于低访问，在某一时刻高访问，需要通过限流慢慢启动，预热时长之后才会慢慢达到单价阈值；
排队等待：排队挨个挨个处理
（3）熔断降级
Sentinel断路器非开即断，没有半开状态；
-
RT(平均响应时间)：当1秒内进入5个请求，平均响应时间均超过阈值，那么接下来的时间窗口之内，调用这个方法就会自动熔断，时间窗口期结束，关闭熔断。默认为4900ms，若要设置上线需要配置；
-
异常比例：当统计时间内，请求次数达到设置数，异常次数达到异常数，则发生熔断，超过熔断时长，关闭熔断；
-
异常数：当统计时间内，请求次数达到设置数，异常比列到达设置比例，则发生熔断，超过熔断时长，关闭熔断；
（4）热点Key规则
- 热点即为经常访问的数据；
- 访问时根据路径是否携带约定参数来决定是否需要限流；
实现：
- 配置：当第一个参数存在，并且1秒内访问超过1次，就使用配置方法。
- 接口：
@SentinelResource(value = "nacosId",blockHandler = "dealHandler")
该注解执行的是配置的热点规则，如果出现java异常，不会执行限流方法；
package com.consumer.Controller;
import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.commons.Entity.Result;
import com.sun.deploy.security.BlockedException;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;
import javax.annotation.Resource;
@RestController
@RequestMapping("nacos/")
@RefreshScope //动态刷新
public class ConsumerController {
@Resource
private RestTemplate restTemplate;
@Value("${spring.datasource.username}")
private String configInfo;
@Value("${service-url.nacos-user-service}")
private String url;
@GetMapping("/{id}")
@SentinelResource(value = "nacosId",blockHandler = "dealHandler")
public Result saveEntity(@PathVariable("id") Integer id,
@RequestParam(value = "p1",required = false) String p1,
@RequestParam(value = "p2",required = false) String p2) {
return restTemplate.getForObject(url+"/nacos/"+id,Result.class);
}
public Result dealHandler(Integer id, String p1, String p2, BlockException blockException){
Result result = new Result(404,"/","");
return result;
}
}
踩坑：com.alibaba.csp.sentinel.slots.block.flow.FlowException
- 是否与原方法参数一致；
- 是否与原方法返回值一致；
- 是否添加BlockException参数；
参数例外项
- 以上例子指定某个位置参数后，就会对该参数进行统计限流，但是有时候希望该参数携带某个特殊值时，对它进行特殊限流规则；
- 当第一个参数值为5时，阈值可达100才会限流；
（5）系统自适应规则
- 从整体维度应用入口进行控制，该规则会对整个服务应用起作用；
| 维度 | 描述 |
|---|---|
| Load自适应 | 系统最高负载，建议取值 CPU cores * 2.5 |
| 并发线程数 | 单机应用的最大线程并发数 |
| 入口QPS | 单机应用维度入口QPS |
| 平均RT | 单机应用所有请求的平均RT |
| CPU使用率 | CPU使用率，取值范围[0, 1] |
5、配置使用
5.1 @SentinelResource配置
不支持private方法；
@RestController
public class RateLimitController {
@GetMapping("/getRate")
@SentinelResource(value = "getRate" ,blockHandler = "error")
public Result get(){
return new Result(200,"正常访问","200");
}
public Result error(BlockException blockException){
return new Result(404,blockException.getClass().getName()+"异常访问","404");
}
}
存在2种配置：
- 使用限流资源名称配置：getRate
- 使用访问Url配置：/getRate
如果有配置blockHandler 方法，则使用该方法，没有则使用系统默认方法；
以上配置导致业务代码和处理代码混合，每个方法都需要配置，导致代码膨胀，改造如下:
- 提出单独的Handler处理规则，注意方法参数值和返回类型要一致
package com.consumer.Handler;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.commons.Entity.Result;
public class BlockHandler {
public static Result error1(BlockException blockException){
return new Result(404,blockException.getClass().getName()+"异常访问1","404");
}
public static Result error2(BlockException blockException){
return new Result(404,blockException.getClass().getName()+"异常访问2","404");
}
}
- 更改注解配置：
@SentinelResource(value = "getRate" ,blockHandlerClass = BlockException.class,blockHandler = "error1")
package com.consumer.Controller;
import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.commons.Entity.Result;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class RateLimitController {
@GetMapping("/getRate")
@SentinelResource(value = "getRate" ,blockHandlerClass = BlockException.class,blockHandler = "error1")
public Result get(){
return new Result(200,"正常访问","200");
}
}
Sentinel核心API：Sphu（定义资源）、Tracer（定义统计）、ContextUtil（定义上下文）
6、整合
6.1 Ribbon搭建
pom.xml
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-sentinelartifactId>
<version>0.9.0.RELEASEversion>
dependency>
<dependency>
<groupId>com.alibaba.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-nacos-configartifactId>
<version>2.2.7.RELEASEversion>
dependency>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
<version>0.9.0.RELEASEversion>
dependency>
application.yml
spring:
application:
name: consumer-nacos
cloud:
nacos:
discovery:
server-addr: 127.0.0.1:8848
config:
server-addr: localhost:8848
file-extension: yaml
sentinel: #配置******************************
transport:
dashboard: localhost:8080
port: 8719 #默认为8719，如果占用会从8719+1开始扫描寻找未占用端口
management: #暴露监控
endpoints:
web:
exposure.include: '*'
主启动
package com.consumer;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
@SpringBootApplication
@EnableDiscoveryClient
public class NacosConsumerDemoApplication {
public static void main(String[] args) {
SpringApplication.run(NacosConsumerDemoApplication.class, args);
}
}
业务Controller
package com.consumer.Controller;
import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.commons.Entity.Result;
import com.sun.deploy.security.BlockedException;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;
import javax.annotation.Resource;
@RestController
@RequestMapping("nacos/")
@RefreshScope //动态刷新
public class ConsumerController {
@Resource
private RestTemplate restTemplate;
@Value("${spring.datasource.username}")
private String configInfo;
@Value("${service-url.nacos-user-service}")
private String url;
@GetMapping("/{id}")
@SentinelResource(value = "nacosId")
public Result saveEntity(@PathVariable("id") Integer id,
@RequestParam(value = "p1",required = false) String p1,
@RequestParam(value = "p2",required = false) String p2) {
return restTemplate.getForObject(url+"/nacos/"+id,Result.class);
}
}
RestTemplate配置
package com.consumer.Config;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;
@Configuration
public class RestTemplateConfig {
@Bean
@LoadBalanced
public RestTemplate getRestTemplate(){
return new RestTemplate();
}
}
6.2 fallback处理运行时异常，blockHandler处理配置违规
只改造业务Controller，其他相同
package com.consumer.Controller;
import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.commons.Entity.Result;
import com.sun.deploy.security.BlockedException;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.client.RestTemplate;
import javax.annotation.Resource;
@RestController
@RequestMapping("nacos/")
@RefreshScope //动态刷新
public class ConsumerController {
@Resource
private RestTemplate restTemplate;
@Value("${spring.datasource.username}")
private String configInfo;
@Value("${service-url.nacos-user-service}")
private String url;
@GetMapping("/{id}")
//fallback处理运行时异常，blockHandler处理配置违规
@SentinelResource(value = "nacosId",fallback = "dealHandler1" ,blockHandler = "dealHandler2")
public Result saveEntity(@PathVariable("id") Integer id,
@RequestParam(value = "p1",required = false) String p1,
@RequestParam(value = "p2",required = false) String p2) {
return restTemplate.getForObject(url+"/nacos/"+id,Result.class);
}
public Result dealHandler1(Integer id, String p1, String p2, BlockException blockException){
Result result = new Result(404,"/","1");
return result;
}
public Result dealHandler2(Integer id, String p1, String p2, BlockException blockException){
Result result = new Result(404,"/","2");
return result;
}
}
当二者同时出现方法调用时，blockHandler 优先级高于fallback ；
异常忽略 exceptionsToIgnore
@GetMapping("/{id}")
@SentinelResource(value = "nacosId",fallback = "dealHandler1" ,blockHandler = "dealHandler2",
exceptionsToIgnore = {IllegalArgumentException.class})
public Result saveEntity(@PathVariable("id") Integer id,
@RequestParam(value = "p1",required = false) String p1,
@RequestParam(value = "p2",required = false) String p2) {
return restTemplate.getForObject(url+"/nacos/"+id,Result.class);
}
配置该属性之后，如果发生IllegalArgumentException异常不会执行fallback 指定方法；
断路方式对比
| Sentinel | Hystrix |
|---|---|
| 信号量隔离 | 线程池、信号量隔离 |
| 基于响应时间、异常比率、异常数 | 基于异常比率 |
| 基于QPS、调用关系限流 | 有限的限流支持 |
7 、规则持久化
- 重启服务，配置的规则回消失，需要将规则持久化保存；
- 可以通过eureka、nacos、consul、redis等持久化媒介实现，官方推荐nacos。
7.1 实现
- pom.xml
<dependency>
<groupId>com.alibaba.cspgroupId>
<artifactId>sentinel-datasource-nacosartifactId>
dependency>
<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>cloud2022artifactId>
<groupId>org.examplegroupId>
<version>1.0-SNAPSHOTversion>
parent>
<modelVersion>4.0.0modelVersion>
<groupId>org.consumer8083groupId>
<artifactId>cloud-alibaba-consumer8083artifactId>
<dependencies>
<dependency>
<groupId>com.alibaba.cspgroupId>
<artifactId>sentinel-datasource-nacosartifactId>
dependency>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-openfeignartifactId>
dependency>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-sentinelartifactId>
<version>0.9.0.RELEASEversion>
dependency>
<dependency>
<groupId>com.alibaba.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-nacos-configartifactId>
<version>2.2.7.RELEASEversion>
dependency>
<dependency>
<groupId>org.springframework.cloudgroupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
<version>0.9.0.RELEASEversion>
dependency>
<dependency>
<groupId>com.commonsgroupId>
<artifactId>commonsartifactId>
<version>1.0-SNAPSHOTversion>
<scope>compilescope>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-webartifactId>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-actuatorartifactId>
dependency>
<dependency>
<groupId>com.baomidougroupId>
<artifactId>mybatis-plus-boot-starterartifactId>
dependency>
<dependency>
<groupId>com.alibabagroupId>
<artifactId>druid-spring-boot-starterartifactId>
<version>1.1.10version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-jdbcartifactId>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-devtoolsartifactId>
<scope>runtimescope>
<optional>trueoptional>
dependency>
<dependency>
<groupId>org.projectlombokgroupId>
<artifactId>lombokartifactId>
<optional>trueoptional>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-testartifactId>
<scope>testscope>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-devtoolsartifactId>
<scope>runtimescope>
<optional>trueoptional>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-autoconfigureartifactId>
dependency>
dependencies>
project>
- application.yml
#数据数据源
datasource:
ds1: #数据源1
nacos:
server-addr: localhost:8848 #nacos地址
dataId: cloudalibaba-sentinel-service #dataId名称
groupId: DEFAULT_GROUP #分组名称
data-type: json #文件类型
rule-type: flow
server:
port: 8083
spring:
application:
name: consumer-nacos
cloud:
nacos:
discovery:
server-addr: 127.0.0.1:8848
config:
server-addr: localhost:8848
file-extension: yaml
sentinel: #配置
transport:
dashboard: localhost:8080
port: 8719 #默认为8719，如果占用会从8719+1开始扫描寻找未占用端口
#数据数据源
datasource:
ds1: #数据源1
nacos:
server-addr: localhost:8848 #nacos地址
dataId: cloudalibaba-sentinel-service #dataId名称
groupId: DEFAULT_GROUP #分组名称
data-type: json #文件类型
rule-type: flow
management: #暴露监控
endpoints:
web:
exposure.include: '*'
#激活feign对sentinel支持
feign:
sentinel:
enabled: true
- 主启动
package com.consumer;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class NacosConsumerDemoApplication {
public static void main(String[] args) {
SpringApplication.run(NacosConsumerDemoApplication.class, args);
}
}
- Nacos设置规则
resourcenacosId：资源名称
limitAppdefalut： 来源应用
grade：阈值类型：0-线程数 1-QPS
count：单机阈值
strategy： 流控模式 0-直接 1-关联 2-链路
controlBehavior：流控效果：0-快速失败 2-WarmUp 3-表示排队等待
clusterModefalse ：是否集群
- Sentinel流控规则
需要调用接口触发，否则此处为空；
总结