在微服务架构中，微服务之间互相依赖较大，相互之间调用必不可免的会失败。但当下游服务A因为瞬时流量导致服务崩溃，其他依赖于A服务的B、C服务由于调用A服务超时耗费了大量的资源，长时间下去，B、C服务也会崩溃。Hystrix就是用来解决服务之间相互调用失败，避免产生蝴蝶效应的熔断器，以及提供降级选项。Hystrix通过隔离服务之间的访问点，阻止它们之间的级联故障以及提供默认选项来实现这一目标，以提高系统的整体健壮性。
它主要解决什么问题?
用来避免由于服务之间依赖较重，出现个别服务宕机、停止服务导致大面积服务雪崩的情况。
一、Maven依赖
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| <dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
</dependencies>
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二、启动类配置
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| package com.springcloud.blog;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient
@EnableCircuitBreaker
@EnableFeignClients
public class BlogRibbonClientApplication {
public static void main(String[] args) {
SpringApplication.run(BlogRibbonClientApplication.class, args);
}
@Bean
@LoadBalanced
RestTemplate restTemplate() {
return new RestTemplate();
}
}
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三、修改配置文件(application.yml)
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| eureka:
client:
fetchRegistry: true
serviceUrl:
defaultZone: http://localhost:8761/eureka/
ribbon:
okhttp:
enabled: true #
NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule # 默认为；轮询，这里改为随机
ConnectTimeout: 5000 # 连接超时时间(ms)
ReadTimeout: 5000 # 通信超时时间(ms)
hystrix:
enabled: true
command:
default:
execution:
isolation:
thread:
timeoutInMilliseconds: 6000 #
server:
port: 8765
spring:
application:
name: blog-ribbon-client
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四、测试类
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| package com.springcloud.blog.example;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
@FeignClient(value="blog-api")
public interface FeignTestService {
@GetMapping("/juhe/getIpInfo")
String getIpInfo(@RequestParam String ip);
}
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五、测试效果
也可以自定义fallback实现返回值，只不过我觉得默认的看起来效果比较好，就直接默认的。
