09.Spring Cloud Alibaba学习笔记--Sentinel服务熔断

熔断框架比较

	Sentinel	Hystrix	resilience4j
隔离策略	信号量隔离（并发线程数限流）	线程池隔离/信号量隔离	信号量隔离
熔断降级策略	基于时间响应、异常比率、异常数	基于异常比率	基于异常比率、响应时间
实时统计实现	滑动窗口（LeapArray）	滑动窗口（基于RxJava）	Ring Bit Buffer
动态规则配置	支持多种数据源	支持多种数据源	有限支持
扩展性	多个扩展点	插件形式	接口形式
基于注解的支持	支持	支持	支持
限流	基于QPS、支持基于调用关系的限流	有限的支持	Rate Limiter

Sentinel整合Ribbon

启动

• Nacos
• Sentinel

创建提供者 9003 / 9004 工程

建 Module

• cloudalibaba-provider-payment9003
• cloudalibaba-provider-payment9004

POM

以 9003 为例，9004 内容类似。

<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>cloud2020artifactId>
        <groupId>demo.yangxu.springcloudgroupId>
        <version>1.0-SNAPSHOTversion>
    parent>
    <modelVersion>4.0.0modelVersion>

    <artifactId>cloudalibaba-provider-payment9003artifactId>

    <dependencies>
        
        <dependency>
            <groupId>com.alibaba.cloudgroupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
        dependency>
        <dependency>
            <groupId>demo.yangxu.springcloudgroupId>
            <artifactId>cloud-api-commonsartifactId>
            <version>${project.version}version>
        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>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>
    dependencies>

project>

YAML

以 9003 为例，9004 内容类似。

application.yaml

server:
  port: 9003

spring:
  application:
    name: nacos-payment-provider
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848 #配置Nacos地址

management:
  endpoints:
    web:
      exposure:
        include: '*'

主启动

以 9003 为例，9004 内容类似。

package demo.yangxu.springcloud.alibaba;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@SpringBootApplication
@EnableDiscoveryClient
public class PaymentMain9003 {
    public static void main(String[] args) {
        SpringApplication.run(PaymentMain9003.class, args);
    }
}

业务类

以 9003 为例，9004 内容类似。

PaymentController

package demo.yangxu.springcloud.alibaba.controller;

import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;

@RestController
public class PaymentController {
    @Value("${server.port}")
    private String serverPort;

    public static HashMap<Long,Payment> hashMap = new HashMap<>();

    static {
        hashMap.put(1L,new Payment(1L,"ae9efb59248d2cdc623eaf0b3f935e65"));
        hashMap.put(2L,new Payment(2L,"ecda3786504e1547b33d167f26a561d3"));
        hashMap.put(3L,new Payment(3L,"f3d1fc3dc268db5f9cacb289295286e6"));
    }

    @GetMapping(value = "/paymentSQL/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id) {
        Payment payment = hashMap.get(id);
        CommonResult<Payment> result = new CommonResult(200,"from mysql,serverPort:  "+serverPort,payment);
        return result;
    }
}

创建消费者 84 工程

建 Module

cloudalibaba-consumer-nacos-order84

POM

<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>cloud2020artifactId>
        <groupId>demo.yangxu.springcloudgroupId>
        <version>1.0-SNAPSHOTversion>
    parent>
    <modelVersion>4.0.0modelVersion>

    <artifactId>cloudalibaba-consumer-nacos-order84artifactId>

    <dependencies>
        
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-openfeignartifactId>
        dependency>
        
        <dependency>
            <groupId>com.alibaba.cloudgroupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
        dependency>
        
        <dependency>
            <groupId>com.alibaba.cloudgroupId>
            <artifactId>spring-cloud-starter-alibaba-sentinelartifactId>
        dependency>
        
        <dependency>
            <groupId>demo.yangxu.springcloudgroupId>
            <artifactId>cloud-api-commonsartifactId>
            <version>${project.version}version>
        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>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>
    dependencies>

project>

YAML

application.yaml

server:
  port: 84


spring:
  application:
    name: nacos-order-consumer
  cloud:
    nacos:
      discovery:
        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

#消费者将要去访问的微服务名称(注册成功进nacos的微服务提供者)
service-url:
  nacos-user-service: http://nacos-payment-provider

# 激活Sentinel对Feign的支持
feign:
  sentinel:
    enabled: true

主启动

OrderNacosMain84

package demo.yangxu.springcloud.alibaba;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@EnableDiscoveryClient
@SpringBootApplication
@EnableFeignClients
public class OrderNacosMain84 {
    public static void main(String[] args) {
        SpringApplication.run(OrderNacosMain84.class,args);
    }
}

业务类

ApplicationContextConfig

package demo.yangxu.springcloud.alibaba.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 ApplicationContextConfig {

    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }
}

Sentinel服务熔断无配置

业务类

CircleBreakerController

package demo.yangxu.springcloud.alibaba.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
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
@Slf4j
public class CircleBreakerController {

    @Value("${service-url.nacos-user-service}")
    private String SERVICE_URL;

    @Resource
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
    @SentinelResource(value = "fallback") //没有配置
    public CommonResult<Payment> fallback(@PathVariable Long id)
    {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id, CommonResult.class,id);

        if (id == 4) {
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }

        return result;
    }

}

测试

启动

• cloudalibaba-provider-payment9003
• cloudalibaba-provider-payment9004
• cloudalibaba-consumer-nacos-order84

访问

http://localhost:84/consumer/fallback/1

返回

{"code":200,"message":"from mysql,serverPort:  9003","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}
//负载均衡
{"code":200,"message":"from mysql,serverPort:  9004","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}

访问

http://localhost:84/consumer/fallback/4

返回

Whitelabel Error Page: java.lang.IllegalArgumentException: IllegalArgumentException,非法参数异常…

访问

http://localhost:84/consumer/fallback/5

返回

Whitelabel Error Page: java.lang.NullPointerException: NullPointerException,该ID没有对应记录,空指针异常

Sentinel服务熔断只配置fallback

业务类

CircleBreakerController

package demo.yangxu.springcloud.alibaba.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
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
@Slf4j
public class CircleBreakerController {

    @Value("${service-url.nacos-user-service}")
    private String SERVICE_URL;

    @Resource
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
    @SentinelResource(value = "fallback",fallback = "handlerFallback") //fallback只负责业务异常
    public CommonResult<Payment> fallback(@PathVariable Long id) {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id, CommonResult.class,id);

        if (id == 4) {
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }

        return result;
    }

    //本例是fallback
    public CommonResult handlerFallback(@PathVariable  Long id,Throwable e) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(444,"兜底异常handlerFallback,exception内容  "+e.getMessage(),payment);
    }

}

测试

启动

• cloudalibaba-provider-payment9003
• cloudalibaba-provider-payment9004
• cloudalibaba-consumer-nacos-order84

访问

http://localhost:84/consumer/fallback/1

返回

{"code":200,"message":"from mysql,serverPort:  9003","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}
//负载均衡
{"code":200,"message":"from mysql,serverPort:  9004","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}

访问

http://localhost:84/consumer/fallback/4

返回

{"code":444,"message":"兜底异常handlerFallback,exception内容  IllegalArgumentException,非法参数异常....","data":{"id":4,"serial":"null"}}

访问

http://localhost:84/consumer/fallback/5

返回

{"code":444,"message":"兜底异常handlerFallback,exception内容  NullPointerException,该ID没有对应记录,空指针异常","data":{"id":5,"serial":"null"}}

Sentinel服务熔断只配置blockHandler

业务类

CircleBreakerController

package demo.yangxu.springcloud.alibaba.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
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
@Slf4j
public class CircleBreakerController {

    @Value("${service-url.nacos-user-service}")
    private String SERVICE_URL;

    @Resource
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
    @SentinelResource(value = "fallback",blockHandler = "blockHandler") //blockHandler只负责sentinel控制台配置违规
    public CommonResult<Payment> fallback(@PathVariable Long id) {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id, CommonResult.class,id);

        if (id == 4) {
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }

        return result;
    }

    //本例是blockHandler
    public CommonResult blockHandler(@PathVariable  Long id, BlockException blockException) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(445,"blockHandler-sentinel限流,无此流水: blockException  "+blockException.getMessage(),payment);
    }

}

Sentinel配置

启动

• cloudalibaba-provider-payment9003
• cloudalibaba-provider-payment9004
• cloudalibaba-consumer-nacos-order84

访问

http://localhost:84/consumer/fallback/1

配置降级规则

测试

1、访问

http://localhost:84/consumer/fallback/1

返回

{"code":200,"message":"from mysql,serverPort:  9003","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}
//负载均衡
{"code":200,"message":"from mysql,serverPort:  9004","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}

2、访问

http://localhost:84/consumer/fallback/4

返回

Whitelabel Error Page: java.lang.IllegalArgumentException: IllegalArgumentException,非法参数异常…

快速刷新

http://localhost:84/consumer/fallback/4

返回

{"code":445,"message":"blockHandler-sentinel限流,无此流水: blockException  null","data":{"id":4,"serial":"null"}}

3、访问

http://localhost:84/consumer/fallback/5

返回

Whitelabel Error Page: java.lang.NullPointerException: NullPointerException,该ID没有对应记录,空指针异常

快速刷新

http://localhost:84/consumer/fallback/5

返回

{"code":445,"message":"blockHandler-sentinel限流,无此流水: blockException  null","data":{"id":5,"serial":"null"}}

Sentinel服务熔断fallback和blockHandle

业务类

CircleBreakerController

package demo.yangxu.springcloud.alibaba.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
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
@Slf4j
public class CircleBreakerController {

    @Value("${service-url.nacos-user-service}")
    private String SERVICE_URL;

    @Resource
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
    @SentinelResource(value = "fallback",fallback = "handlerFallback",blockHandler = "blockHandler")
    public CommonResult<Payment> fallback(@PathVariable Long id) {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id, CommonResult.class,id);

        if (id == 4) {
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }

        return result;
    }

    //本例是fallback
    public CommonResult handlerFallback(@PathVariable  Long id,Throwable e) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(444,"兜底异常handlerFallback,exception内容  "+e.getMessage(),payment);
    }

    //本例是blockHandler
    public CommonResult blockHandler(@PathVariable  Long id, BlockException blockException) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(445,"blockHandler-sentinel限流,无此流水: blockException  "+blockException.getMessage(),payment);
    }

}

Sentinel配置

启动

• cloudalibaba-provider-payment9003
• cloudalibaba-provider-payment9004
• cloudalibaba-consumer-nacos-order84

访问

http://localhost:84/consumer/fallback/1

配置流控规则

测试

1、访问

http://localhost:84/consumer/fallback/1

返回

{"code":200,"message":"from mysql,serverPort:  9003","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}
//负载均衡
{"code":200,"message":"from mysql,serverPort:  9004","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}

快速刷新

http://localhost:84/consumer/fallback/1

返回

{"code":445,"message":"blockHandler-sentinel限流,无此流水: blockException  null","data":{"id":1,"serial":"null"}}

2、访问

http://localhost:84/consumer/fallback/4

返回

{"code":444,"message":"兜底异常handlerFallback,exception内容  IllegalArgumentException,非法参数异常....","data":{"id":4,"serial":"null"}}

快速刷新

http://localhost:84/consumer/fallback/4

返回

{"code":445,"message":"blockHandler-sentinel限流,无此流水: blockException  null","data":{"id":1,"serial":"null"}}

3、访问

http://localhost:84/consumer/fallback/5

返回

{"code":444,"message":"兜底异常handlerFallback,exception内容  NullPointerException,该ID没有对应记录,空指针异常","data":{"id":5,"serial":"null"}}

快速刷新

http://localhost:84/consumer/fallback/5

返回

{"code":445,"message":"blockHandler-sentinel限流,无此流水: blockException  null","data":{"id":5,"serial":"null"}}

Sentinel服务熔断exceptionsToIgnore

业务类

CircleBreakerController

package demo.yangxu.springcloud.alibaba.controller;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import lombok.extern.slf4j.Slf4j;
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
@Slf4j
public class CircleBreakerController {

    @Value("${service-url.nacos-user-service}")
    private String SERVICE_URL;

    @Resource
    private RestTemplate restTemplate;

    @RequestMapping("/consumer/fallback/{id}")
    @SentinelResource(value = "fallback",fallback = "handlerFallback",blockHandler = "blockHandler",
            exceptionsToIgnore = {IllegalArgumentException.class})
    public CommonResult<Payment> fallback(@PathVariable Long id) {
        CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/paymentSQL/"+id, CommonResult.class,id);

        if (id == 4) {
            throw new IllegalArgumentException ("IllegalArgumentException,非法参数异常....");
        }else if (result.getData() == null) {
            throw new NullPointerException ("NullPointerException,该ID没有对应记录,空指针异常");
        }

        return result;
    }

    //本例是fallback
    public CommonResult handlerFallback(@PathVariable  Long id,Throwable e) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(444,"兜底异常handlerFallback,exception内容  "+e.getMessage(),payment);
    }

    //本例是blockHandler
    public CommonResult blockHandler(@PathVariable  Long id, BlockException blockException) {
        Payment payment = new Payment(id,"null");
        return new CommonResult<>(445,"blockHandler-sentinel限流,无此流水: blockException  "+blockException.getMessage(),payment);
    }

}

测试

启动

• cloudalibaba-provider-payment9003
• cloudalibaba-provider-payment9004
• cloudalibaba-consumer-nacos-order84

1、访问

http://localhost:84/consumer/fallback/4

返回

Whitelabel Error Page: java.lang.IllegalArgumentException: IllegalArgumentException,非法参数异常…

2、访问

http://localhost:84/consumer/fallback/5

返回

{"code":444,"message":"兜底异常handlerFallback,exception内容  NullPointerException,该ID没有对应记录,空指针异常","data":{"id":5,"serial":"null"}}

总结

fallback 管运行时异常，blockHandler 管配置违规。

若 blockHandler 和 fallback 都进行了配置，则被限流降级而抛出 BlockException 时只会进入 blockHandler 处理逻辑。

Sentinel整合OpenFeign

修改 cloudalibaba-consumer-nacos-order84

84 消费端调用提供者 9003 / 9004，OpenFeign 组件一般是消费侧。

POM

<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>cloud2020artifactId>
        <groupId>demo.yangxu.springcloudgroupId>
        <version>1.0-SNAPSHOTversion>
    parent>
    <modelVersion>4.0.0modelVersion>

    <artifactId>cloudalibaba-consumer-nacos-order84artifactId>

    <dependencies>
        
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-openfeignartifactId>
        dependency>
        
        <dependency>
            <groupId>com.alibaba.cloudgroupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discoveryartifactId>
        dependency>
        
        <dependency>
            <groupId>com.alibaba.cloudgroupId>
            <artifactId>spring-cloud-starter-alibaba-sentinelartifactId>
        dependency>
        
        <dependency>
            <groupId>demo.yangxu.springcloudgroupId>
            <artifactId>cloud-api-commonsartifactId>
            <version>${project.version}version>
        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>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>
    dependencies>

project>

YAML

application.yaml

server:
  port: 84


spring:
  application:
    name: nacos-order-consumer
  cloud:
    nacos:
      discovery:
        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

#消费者将要去访问的微服务名称(注册成功进nacos的微服务提供者)
service-url:
  nacos-user-service: http://nacos-payment-provider

# 激活Sentinel对Feign的支持
feign:
  sentinel:
    enabled: true

主启动

OrderNacosMain84

package demo.yangxu.springcloud.alibaba;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@EnableDiscoveryClient
@SpringBootApplication
@EnableFeignClients
public class OrderNacosMain84 {
    public static void main(String[] args) {
        SpringApplication.run(OrderNacosMain84.class,args);
    }
}

业务类

PaymentService

带 @FeignClient 注解的业务接口

package demo.yangxu.springcloud.alibaba.service;

import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

@FeignClient(value = "nacos-payment-provider",fallback = PaymentFallbackService.class)
public interface PaymentService {
    @GetMapping(value = "/paymentSQL/{id}")
    public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id);
}

PaymentFallbackService

package demo.yangxu.springcloud.alibaba.service;

import demo.yangxu.springcloud.entities.CommonResult;
import demo.yangxu.springcloud.entities.Payment;
import org.springframework.stereotype.Component;

@Component
public class PaymentFallbackService implements PaymentService {
    @Override
    public CommonResult<Payment> paymentSQL(Long id) {
        return new CommonResult<>(44444,
                "服务降级返回,---PaymentFallbackService",
                new Payment(id,"errorSerial"));
    }
}

CircleBreakerController

添加以下代码：

//==================OpenFeign
@Resource
private PaymentService paymentService;

@GetMapping(value = "/consumer/paymentSQL/{id}")
public CommonResult<Payment> paymentSQL(@PathVariable("id") Long id) {
    return paymentService.paymentSQL(id);
}

测试

访问

http://localhost:84/consumer/paymentSQL/1

返回

{"code":200,"message":"from mysql,serverPort:  9003","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}
//负载均衡
{"code":200,"message":"from mysql,serverPort:  9004","data":{"id":1,"serial":"ae9efb59248d2cdc623eaf0b3f935e65"}}

关闭 9003 / 9004 微服务提供者

访问

http://localhost:84/consumer/paymentSQL/1

返回

{"code":44444,"message":"服务降级返回,---PaymentFallbackService","data":{"id":1,"serial":"errorSerial"}}

84 消费侧会自动降级，不会被耗死。