1、介紹

Spring Cloud Circuit breaker provides an abstraction across different circuit breaker implementations. It provides a consistent API to use in your applications allowing you the developer to choose the circuit breaker implementation that best fits your needs for your app.

Spring Cloud斷路器提供了一個跨不同斷路器的抽象實現。它提供了在您的應用程式中使用的一致的API，允許您的開發人員選擇最適合您的應用程式需要的斷路器實現。

支援斷路器實現有以下幾種

• Netfix Hystrix (Spring Cloud官方已經不予支援)
• Resilience4J （支援）
• Sentinel
• Spring Retry

2、快速開始

pom.xml
maven依賴配置檔案，如下：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.4</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <groupId>com.mindasoft</groupId>
    <artifactId>spring-cloud-circuitbreaker-consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-cloud-circuitbreaker-consumer</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <spring-cloud.version>2021.0.1</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-circuitbreaker-resilience4j</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-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>nexus-aliyun</id>
            <name>Nexus aliyun</name>
            <url>https://maven.aliyun.com/repository/public</url>
            <layout>default</layout>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
            <releases>
                <enabled>true</enabled>
            </releases>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>nexus-aliyun</id>
            <name>Nexus aliyun</name>
            <url>https://maven.aliyun.com/repository/public</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
            <releases>
                <enabled>true</enabled>
            </releases>
        </pluginRepository>
    </pluginRepositories>

</project>
 

比上個專案多瞭如下配置：

  <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-circuitbreaker-resilience4j</artifactId>
        </dependency>

使用resilience4j 實現斷路器。

application.properties

server.port=9004

# 服務註冊中心地址
eureka.client.service-url.defaultZone=http://localhost:9000/eureka/

# 服務名稱
spring.application.name=circuitbreaker-customer

 

SpringCloudCircuitBreakerConsumerApplication

package com.mindasoft;

import io.github.resilience4j.circuitbreaker.CircuitBreakerConfig;
import io.github.resilience4j.timelimiter.TimeLimiterConfig;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.circuitbreaker.resilience4j.Resilience4JCircuitBreakerFactory;
import org.springframework.cloud.circuitbreaker.resilience4j.Resilience4JConfigBuilder;
import org.springframework.cloud.client.circuitbreaker.Customizer;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

import java.time.Duration;

@EnableDiscoveryClient // Eureka Discovery Client 標識
@SpringBootApplication
public class SpringCloudCircuitBreakerConsumerApplication {

    // 開啟負載均衡的功能
    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }

    @Bean
    public Customizer<Resilience4JCircuitBreakerFactory> defaultCustomizer() {
        return factory -> factory.configureDefault(id -> new Resilience4JConfigBuilder(id)
                .timeLimiterConfig(TimeLimiterConfig.custom().timeoutDuration(Duration.ofSeconds(3)).build())
                .circuitBreakerConfig(CircuitBreakerConfig.ofDefaults())
                .build());
    }

    public static void main(String[] args) {
        SpringApplication.run(SpringCloudCircuitBreakerConsumerApplication.class, args);
    }

}

ConsumerController

package com.mindasoft.consumer;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.circuitbreaker.CircuitBreakerFactory;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * Created by huangmin on 2017/11/10 14:50.
 */
@RestController
public class ConsumerController {

    private static final Logger LOGGER = LoggerFactory.getLogger(ConsumerController.class);

    @Autowired
    private RestTemplate restTemplate; // HTTP 訪問操作類
    @Autowired
    private CircuitBreakerFactory circuitBreakerFactory;

    @RequestMapping("/hello")
    public String hello() {
        String providerMsg = circuitBreakerFactory.create("hello")
                .run(() -> restTemplate.getForObject("http://PROVIDER-SERVICE/hello", String.class),
                        throwable -> "CircuitBreaker fallback msg");

        return "Hello,I'm Customer! msg from provider : <br/><br/> " + providerMsg;
    }

}

啟動eureka server和本專案，訪問http://127.0.0.1:9004/hello
頁面列印如下：

Hello,I'm Customer! msg from provider :

CircuitBreaker fallback msg

說明進入到了斷路throwable 處理邏輯。