SpringCloud教程 | 第4篇:断路器（Hystrix）

一、断路器简介

在微服务架构中，根据业务来拆分成一个个的服务，服务与服务之间可以相互调用（RPC），在Spring Cloud可以用RestTemplate+Ribbon和Feign来调用。为了保证其高可用，单个服务通常会集群部署。由于网络原因或者自身的原因，服务并不能保证100%可用，如果单个服务出现问题，调用这个服务就会出现线程阻塞，此时若有大量的请求涌入，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。

创建Module->microservicecloud-provider-dept-hystrix

1.服务提供者POM配置 (ribbon方式熔断配置)

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>mall</artifactId>
        <groupId>com.linjia</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>microservicecloud-provider-dept-hystrix</artifactId>

    <name>microservicecloud-provider-dept-hystrix</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.linjia</groupId>
            <artifactId>microservicecloud-api</artifactId>
            <version>${project.version}</version>
        </dependency>
        <!-- hystrix -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-hystrix</artifactId>
        </dependency>
        <!-- actuator监控信息完善 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <!-- 将微服务provider侧注册进eureka -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jetty</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>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>
    </dependencies>

    <build>
        <finalName>${name}</finalName>
        <!-- 打包jar名称-->
        <plugins>
            <plugin><!-- 打包可运行的jar  -->
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

        </plugins>
    </build>
</project>

2.服务提供者yml配置 

server:
  port: 8002

mybatis:
  type-aliases-package: com.linjia.springcloud.entity          # 所有Entity别名类所在包
  mapper-locations:
  - classpath:mybatis/mapper/*.xml                       # mapper映射文件

spring:
  application:
    name: microservicecloud-dept
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource            # 当前数据源操作类型
    driver-class-name: org.gjt.mm.mysql.Driver              # mysql驱动包
    url: jdbc:mysql://192.168.0.38:3306/test              # 数据库名称
    username: root
    password: linjia
    dbcp2:
      min-idle: 5                                           # 数据库连接池的最小维持连接数
      initial-size: 5                                       # 初始化连接数
      max-total: 5                                          # 最大连接数
      max-wait-millis: 200                                  # 等待连接获取的最大超时时间
  jpa:
      hibernate:
        ddl-auto: update
      show-sql: true
      properties:
            hibernate.format_sql: true
      database-platform: org.hibernate.dialect.MySQL5InnoDBDialect

eureka:
  client:
    service-url:
       # defaultZone: http://localhost:7001/eureka   #将客户端注册进eureka服务列表内
        defaultZone: http://localhost:7001/eureka,http://localhost:7002/eureka,http://localhost:7003/eureka
  instance:
    instance-id: ${spring.cloud.client.ipAddress}-hystrix:${server.port}   #自定义服务名称信息  启动多个服务做集群需要设置为不同的ID值
    prefer-ip-address: true   #访问路径可以显示IP地址
    leaseRenewalIntervalInSeconds: 10          #剔除不健康节点。
    leaseExpirationDurationInSeconds: 30       #剔除不健康节点。

info:
  app.name: microservicecloud-dept
  company.name: www.baidu.cn
  build.artifactId: $project.artifactId$
  build.version: $project.version$

3.服务提供者yml配置 

   

package com.linjia;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.context.annotation.ComponentScan;

/**
 * Hello world!
 *
 */
@SpringBootApplication
@ComponentScan("com.linjia.springcloud")
@EnableEurekaClient//启动服务注册
@EnableDiscoveryClient
@EnableHystrix
public class HystrixProviderApplication
{
    public static void main( String[] args )
    {
        SpringApplication.run(HystrixProviderApplication.class, args);
    }
}

4.服务提供者Controller  

package com.linjia.springcloud.controller;

import com.linjia.springcloud.entity.Dept;
import com.linjia.springcloud.service.DeptService;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;


/**
 * @date 2018/5/14
 */
@RestController
public class DeptController {
    private static final Logger logger= LoggerFactory.getLogger(DeptController.class);
    @Autowired
    private DeptService service;

    @RequestMapping(value = "/dept/get/{id}", method = RequestMethod.GET)
    //在ribbon使用断路器
    //一旦调用服务方法失败并抛出了错误信息后，会自动调用@HystrixCommand标注好的fallbackMethod调用类中的指定方法
    @HystrixCommand(fallbackMethod = "processHystrix")
    public Dept get(@PathVariable("id") Long id)
    {
        Dept dept = this.service.get(id);
        if (null == dept) {
            throw new RuntimeException("该ID：" + id + "没有没有对应的信息");
        }
        return dept;
    }

    public Dept processHystrix(@PathVariable("id") Long id)
    {
        return new Dept(id,"该ID：" + id + "没有没有对应的信息,null--@HystrixCommand","no this database in MySQL");
    }

}

启动注册中心，服务提供者，消费者，访问http://localhost/consumer/dept/get/11

 返回：

{"deptno":11,"dname":"该ID：11没有没有对应的信息,null--@HystrixCommand","db_source":"no this database in MySQL"}

方式二.服务提供者POM配置 (feign方式熔断配置)feign.hystrix

  修改  microservicecloud-api 配置

  2.1 新建 DeptClientServiceFallbackFactory 

package com.linjia.springcloud.service;

import com.linjia.springcloud.entity.Dept;
import feign.hystrix.FallbackFactory;
import org.springframework.stereotype.Component;

import java.util.List;

@Component // 不要忘记添加，不要忘记添加
public class DeptClientServiceFallbackFactory implements FallbackFactory<DeptClientService>
{
	@Override
	public DeptClientService create(Throwable throwable)
	{
		return new DeptClientService() {
			@Override
			public Dept get(long id)
			{
                return new Dept(id,"该ID：" + id + "没有没有对应的信息,Consumer客户端提供的降级信息,此刻服务Provider已经关闭","no this database in MySQL");
			}

			@Override
			public List<Dept> list()
			{
				return null;
			}

			@Override
			public boolean add(Dept dept)
			{
				return false;
			}
		};
	}
}

2.2 修改DeptClientService接口注释

package com.linjia.springcloud.service;
import com.linjia.springcloud.entity.Dept;
import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import java.util.List;


/**
 * 
 * @Description: 修改microservicecloud-api工程，根据已经有的DeptClientService接口
 * @author
 * @date 2018年4月21日
 */
//@FeignClient(value = "MICROSERVICECLOUD-DEPT")
@FeignClient(value = "MICROSERVICECLOUD-DEPT",fallbackFactory=DeptClientServiceFallbackFactory.class)
public interface DeptClientService
{
	@RequestMapping(value = "/dept/get/{id}", method = RequestMethod.GET)
	public Dept get(@PathVariable("id") long id);

	@RequestMapping(value = "/dept/list", method = RequestMethod.GET)
	public List<Dept> list();

	@RequestMapping(value = "/dept/add", method = RequestMethod.POST)
	public boolean add(Dept dept);
}

运行：启动注册中心，消息提供者，启动

microservicecloud-consumer-dept-feign (参考其他章节) 访问：

http://localhost:8089/consumer/dept/get/11  返回JSON:

{"deptno":11,"dname":"该ID：11没有没有对应的信息,Consumer客户端提供的降级信息,此刻服务Provider已经关闭","db_source":"no this database in MySQL"}