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/eureka
  instance:
    prefer-ip-address: true
    instance-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 {
 
    @Autowired
    private 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-USER
        return 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
    @LoadBalanced
    public 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/eureka
  instance:
    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-USER
  appConfig: customer-user
  clusterNameExpression: "'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。