1.什么是Resilience4J？

Netflix Hystrix 断路器是 Spring Cloud 中最早就开始支持的一种服务调用容错解决方案，但是目前的 Hystrix 已经处于维护模式了，虽然这并不影响已经上线的项目，并且在短期内，你甚至也可以继续在项目中使用 Hystrix 。但是长远来看，处于维护状态的 Hystrix 走下历史舞台只是一个时间问题，特别是在 Spring Cloud Greenwich 版中，官方已经给出了 Hystrix 的建议替代方案。如下图：

，它专为 Java 8 和函数式编程而设计。 Resilience4j 非常轻量级，因为它的库只使用 Vavr （以前称为 Javaslang ），它没有任何其他外部库依赖项。相比之下， Netflix Hystrix 对Archaius 具有编译依赖性，这导致了更多的外部库依赖，例如 Guava 和 Apache Commons 。而如果使用Resilience4j，你无需引用全部依赖，可以根据自己需要的功能引用相关的模块即可。 Resilience4j 也提供了一系列增强微服务可用性的功能，主要功能如下：

断路器
限流
基于信号量的隔离
缓存
限时
请求重试

今天我么主要讲解断路器是如何实现的？

2.实验工程

实验目的

实现断路器功能

pom.xml

<?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>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-parent</artifactId>        <version>3.2.1</version>    </parent>    <modelVersion>4.0.0</modelVersion>
    <artifactId>resilience4j</artifactId>
    <properties>        <maven.compiler.source>17</maven.compiler.source>        <maven.compiler.target>17</maven.compiler.target>    </properties>    <dependencies>

        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>
        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-autoconfigure</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-test</artifactId>            <scope>test</scope>        </dependency>
        <dependency>            <groupId>io.github.resilience4j</groupId>            <artifactId>resilience4j-spring-boot3</artifactId>            <version>2.0.2</version>        </dependency>        <dependency>            <groupId>org.projectlombok</groupId>            <artifactId>lombok</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-aop</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-actuator</artifactId>        </dependency>
    </dependencies></project>

controller

package com.et.resilience4j.controller;
import com.et.resilience4j.model.Activity;import io.github.resilience4j.circuitbreaker.annotation.CircuitBreaker;import lombok.extern.slf4j.Slf4j;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.http.ResponseEntity;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;import org.springframework.web.client.RestTemplate;
@Slf4j@RequestMapping("/activity")@RestControllerpublic class ActivityController {
    private RestTemplate restTemplate;
    private final String BORED_API = "http://www.liuhaihua.cn/api/activity";
    public ActivityController(RestTemplate restTemplate) {        this.restTemplate = restTemplate;    }
    @GetMapping    @CircuitBreaker(name = "randomActivity", fallbackMethod = "fallbackRandomActivity")    public String getRandomActivity() {        ResponseEntity<Activity> responseEntity = restTemplate.getForEntity(BORED_API, Activity.class);        Activity activity = responseEntity.getBody();        log.info("Activity received: " + activity.getActivity());        return activity.getActivity();    }
    public String fallbackRandomActivity(Throwable throwable) {        return "fail to read a Activity from HBLOG";    }
}

entity

package com.et.resilience4j.model;
import lombok.AllArgsConstructor;import lombok.Data;import lombok.NoArgsConstructor;
/* sample message    {        "activity": "Start a family tree",            "type": "social",            "participants": 1,            "price": 0,            "link": "https://en.wikipedia.org/wiki/Family_tree",            "key": "6825484",            "accessibility": 1    }*/@NoArgsConstructor@AllArgsConstructor@Datapublic class Activity {    private String activity;    private String type;    private String link;    private String key;    private Integer participants;    private Double price;    private Double accessibility;}

DemoApplication.java

package com.et.resilience4j;
import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.context.annotation.Bean;import org.springframework.web.client.RestTemplate;
@SpringBootApplicationpublic class DemoApplication {
   public static void main(String[] args) {      SpringApplication.run(DemoApplication.class, args);   }
   @Bean   public RestTemplate restTemplate() {      return new RestTemplate();   }
}

application.yaml

spring:  application.name: resilience4j-demo  jackson.serialization.indent_output: true
management:  endpoints.web.exposure.include:    - '*'  endpoint.health.show-details: always  health.circuitbreakers.enabled: true
resilience4j.circuitbreaker:  configs:    default:      registerHealthIndicator: true      slidingWindowSize: 10      minimumNumberOfCalls: 5      permittedNumberOfCallsInHalfOpenState: 3      automaticTransitionFromOpenToHalfOpenEnabled: true      waitDurationInOpenState: 5s      failureRateThreshold: 50      eventConsumerBufferSize: 10

以上只是一些关键代码，所有代码请参见下面代码仓库

代码仓库

https://github.com/Harries/springboot-demo(Resilience4J)

3.测试

启动Spring Boot应用工程
访问http://127.0.0.1:8080/activity
返回fail to read a Activity from HBLOG

4.引用

https://docs.spring.io/spring-cloud-commons/docs/current/reference/html/#spring-cloud-circuit-breaker

ITPub博客

Spring Boot集成Resilience4J实现断路器功能