微服务架构中，微服务之间相互调用，springcloud可以用feign方式和RestTemplate+ribbon方式来实现服务间的相互调用。但如果某一个服务出现问题，所有调用该出问题的服务都将出现阻塞，如果有大量的请求，则Servlet容器的线程资源会被消耗完毕，导致服务瘫痪。服务与服务之间的依赖性，故障会传播，会对整个微服务系统造成灾难性的严重后果，这就是服务故障的“雪崩”效应。
为了解决这个问题，业界提出了断路器模型。
1.ribbon中使用断路器hystrix
build.gradle文件
buildscript {
ext {
springBootVersion = '2.0.4.RELEASE'
}
repositories {
mavenCentral()
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
}
}
apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'
group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8
repositories {
mavenCentral()
}
ext {
springCloudVersion = 'Finchley.SR1'
}
dependencies {
compile('org.springframework.boot:spring-boot-starter-web')
compile('org.springframework.cloud:spring-cloud-starter-netflix-eureka-client')
compile('org.springframework.cloud:spring-cloud-starter-netflix-hystrix')
compile('org.springframework.cloud:spring-cloud-starter-netflix-ribbon')
testCompile('org.springframework.boot:spring-boot-starter-test')
}
dependencyManagement {
imports {
mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
}
}
application.yml文件
server:
port: 8797
spring:
application:
name: service-ribbon-hystrix
eureka:
client:
service-url:
defaultZone: http://localhost:8791/eureka/
主方法
package com.example.serviceribbonhystrix;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
@EnableHystrix
@EnableEurekaClient
@SpringBootApplication
public class ServiceRibbonHystrixApplication {
public static void main(String[] args) {
SpringApplication.run(ServiceRibbonHystrixApplication.class, args);
}
@Bean
RestTemplate restTemplate() {
return new RestTemplate();
}
}
HelloService.java文件
package com.example.serviceribbonhystrix;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
@Service
public class HelloService {
@Autowired
RestTemplate restTemplate;
@HystrixCommand(fallbackMethod = "errorMsg")
public String hiService() {
return restTemplate.getForObject("http://EUREKA-CLIENT-SAY-HI/hi", String.class);
}
public String errorMsg(){
return "I am ribbon with hystrix,Wrong!";
}
}
HelloController.java文件
package com.example.serviceribbonhystrix;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloController {
@Autowired
HelloService helloService;
@RequestMapping("/hi")
public String sayHi() {
return helloService.hiService();
}
}
只是单独启动该服务，不启动eureka-client-say-hi服务，访问http://localhost:8797/hi
返回要返回的信息，此时断路器已经生效了：
2.feign中使用断路器hystrix
因为feign是自带断路器的，所以依赖中就不需要加hystrix
build.gradle
buildscript {
ext {
springBootVersion = '2.0.4.RELEASE'
}
repositories {
mavenCentral()
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
}
}
apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'
group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8
repositories {
mavenCentral()
}
ext {
springCloudVersion = 'Finchley.SR1'
}
dependencies {
compile('org.springframework.boot:spring-boot-starter-web')
compile('org.springframework.cloud:spring-cloud-starter-netflix-eureka-client')
compile('org.springframework.cloud:spring-cloud-starter-openfeign')
testCompile('org.springframework.boot:spring-boot-starter-test')
}
dependencyManagement {
imports {
mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
}
}
application.yml文件
server:
port: 8796
spring:
application:
name: service-feign-hystrix
eureka:
client:
service-url:
defaultZone: http://localhost:8791/eureka/
feign:
hystrix:
enabled: true #feign自带断路器，但需要打开
主方法：
package com.example.servicefeignhystrix;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@EnableEurekaClient
@EnableFeignClients
@SpringBootApplication
public class ServiceFeignHystrixApplication {
public static void main(String[] args) {
SpringApplication.run(ServiceFeignHystrixApplication.class, args);
}
}
接口SayHiService.java文件
package com.example.servicefeignhystrix;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@FeignClient(value = "eureka-client-say-hi",fallback = SayHiServiceWithHystrix.class)
public interface SayHiService {
@RequestMapping(value = "/hi", method = RequestMethod.GET)
String sayHiFromClient();
}
SayHiServiceWithHystrix.java文件
package com.example.servicefeignhystrix;
import org.springframework.stereotype.Component;
@Component
public class SayHiServiceWithHystrix implements SayHiService {
@Override
public String sayHiFromClient() {
return "sorry,I am wrong";
}
}
HelloController.java文件
package com.example.servicefeignhystrix;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloController {
@Autowired
SayHiService sayHiService;
@RequestMapping("/hi")
public String sayHi(){
return sayHiService.sayHiFromClient();
}
}
此时启动eureka-server，以及eureka-client-say-hi项目的两个实例，以及刚才新建的项目service-feign-hystrix.
访问http://localhost:8796/hi
出现以下两种场景：
和
如果关掉8792端口的服务，则会返回hi,I am port 8793
如果关掉eureka-client-say-hi服务的8792和8793两个端口实例，则会返回
此时标明，feign的断路器已经生效了。
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