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hystrix主要作用在服务消费者，进行应用的保护，当请求的服务请求超时时，做出相应的处理，避免客户端一直进行请求等待，避免在高并发的情况出现服务器死机（请求过多，内存不足）

接下来的通过一个案例对hystrix的使用进行说明，案例完成的功能：

服务消费者根据Id调用服务提供者的接口，获取User表单的对应的记录，若请求超时则返回id为-1的User记录

一、基于Ribbon

<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.5.2.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><java.version>1.8</java.version><mybatis-spring-boot.version>1.2.0</mybatis-spring-boot.version><mysql-connector.version>5.1.39</mysql-connector.version>
</properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka</artifactId><version>1.3.5.RELEASE</version></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-hystrix</artifactId><version>1.3.5.RELEASE</version></dependency></dependencies>

2、application.yml

server:port: 8089
spring:application:name: customer-user
eureka:client: serviceUrl: defaultZone: http://user:zj123@localhost:8761/eurekainstance:prefer-ip-address: trueinstance-id: ${spring.application.name}:${spring.cloud.client.ipAddress}:${spring.application.instance_id:${server.port}}
provider-user: ribbon: NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule

3、Controller调用类

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.zhuojing.bean.User;@RestController
public class UserController {@Autowiredprivate RestTemplate restTemplate;@GetMapping(value="/simple/{id}",produces=MediaType.APPLICATION_JSON_VALUE+";charset=utf-8")@HystrixCommand(fallbackMethod = "findByIdFallback")public User findUserById(@PathVariable Long id){//服务提供者地址 PROVIDER-USERreturn this.restTemplate.getForObject("http://PROVIDER-USER/simple/"+id, User.class);}/*** 断路器模式，当请求的消费者provider-user超时的情况下，就会直接调用此方法，此方法的参数和返回类型必须和findUserById方法一致，请求超时时间为1秒* @param id* @return*/public User findByIdFallback(Long id){User user = new User();user.setId(0L);return user;}}

hystrix的默认的超时时间为1秒，若自定hystrix超时时间有一下两种方式

a、@HystrixCommand注解配置

@HystrixCommand(fallbackMethod = "findByIdFallback",commandProperties = {@HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value = "3000")
})

b、在application.yml配置

hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds: 5000

4、启动类

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.ribbon.RibbonClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.FilterType;
import org.springframework.web.client.RestTemplate;@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker
public class AppCusRibbonPropertiesTest {@Bean@LoadBalancedpublic RestTemplate restTemplate(){return new RestTemplate();}public static void main(String[] args) {SpringApplication.run(AppCusRibbonPropertiesTest.class, args);}
}

二、dashboard的使用

1、pom.xml

<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.5.2.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-hystrix-dashboard</artifactId><version>1.3.5.RELEASE</version></dependency></dependencies>

2、application.yml

server:
port: 8030

3、启动类

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;@EnableHystrixDashboard
@SpringBootApplication
public class DashboardApplication {public static void main(String[] args) {SpringApplication.run(DashboardApplication.class, args);}
}

启动后访问：http:/ /localhost:8030/hystrix 进入首页，在地址栏上输入http:/ /localhost:8089/hystrix.stream（hystrix.stream）进行监控，在使用了hystrix的服务调用后才有数据。

三、Turbine的使用，Turbine是对微服务集群的监听

1、pom.xml

<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.5.2.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-turbine</artifactId><version>1.3.5.RELEASE</version></dependency></dependencies>

2、application.yml

server:port: 8031
spring:application:name: microservice-hystrix-turbine
eureka:client:serviceUrl:defaultZone: http://user:zj123@localhost:8761/eurekainstance:prefer-ip-address: true
turbine:aggregator:clusterConfig: default  #默认defualt，只有一个服务时候可以写服务名称的大写CUSTOMER-USERappConfig: customer-userclusterNameExpression: "'default'"

3、启动类

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.turbine.EnableTurbine;@EnableTurbine
@SpringBootApplication
public class TurbineApplication {public static void main(String[] args) {SpringApplication.run(TurbineApplication.class, args);}
}

hystrix 主页面中将localhost:8031/turbine.stream?cluster=CUSTOMER-USER填入，便可进行数据的图像化。

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