标题
Hystrix是一个用于处理分布式系统的延迟和容错的开源库,在分布式系统里,许多依赖不可避免的会调用失败,比如超时,异常等,Hystrix能够保证在一个依赖出问题的情况下,不会导致整体服务失败,避免级联故障,以提高分布式系统的弹性;
"断路器"本身是一种开关装置,当某个服务单元发生故障之后,通过断路器的故障监控(类似熔断保险丝),向调用方返回一个符合预期的,可处理的备选响应(FallBack),而不是长时间的等待或者抛出调用方无法处理的异常,这样就保证了服务调用方的线程不会被长时间,不必要的占用,从而避免了故障在分布式系统中的蔓延,乃至雪崩;
服务熔断
熔断机制是应对雪崩效应的一种微服务链路保护机制;
当扇出链路的某个微服务不可用或者响应时间太长时,会进行服务的将几,进而熔断该节点微服务的调用,快速返回"错误"的响应信息,当检测到该节点微服务调用响应正常后恢复调用链路,在springcloud框架里熔断机制通过Hystrix实现,Hystrix会监控微服务间调用的状况,当失败的调用到一定阈值,缺省是5秒内20次调用失败就会启动熔断机制,熔断机制的注解是@HystrixCommand
创建microservicecloud-provider-dept-hystrix-8001
编写microservicecloud-provider-dept-hystrix-8001的pom.xml
<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">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.yt.springcloud</groupId>
<artifactId>microservicecloud</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<artifactId>microservicecloud-provider-dept-hystrix-8001</artifactId>
<dependencies>
<!-- hystrix -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</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>
<!-- 引入自己已定义的api通用包,可以使用Dept部门Entity -->
<dependency>
<groupId>com.yt.springcloud</groupId>
<artifactId>microservicecloud-api</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-config</artifactId>
</dependency>
<!-- actuator监控信息完善 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</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>
<!-- 修改后立即生效，热部署 -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>springloaded</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>
</dependencies>
</project>
编写microservicecloud-provider-dept-hystrix-8001的application.yml
server:
port: 8001 # 当前微服务的端口
mybatis:
config-location: classpath:mybatis/mybatis.cfg.xml # mybatis配置文件所在路径
type-aliases-package: com.yt.springcloud.entity # 所有饿entity实体类所在包
mapper-locations:
- classpath:mybatis/mapper/**/*.xml # mapper映射文件
spring:
application:
name: microservicecloud-dept # 对外暴露的微服务的名字(很重要)
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://localhost:3306/cloudDB01 # 数据库名称
username: root
password: hannong
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
eureka:
client: #客户端注册进eureka服务列表内
service-url:
defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/ #去注册中心的地址
#defaultZone:7001,7002,7003 去注册中心的地址
instance:
instance-id: microservicecloud-dept8001-hystrix #自定义hystrix相关的服务名称信息
prefer-ip-address: true #访问路径可以显示ip地址
info:
app.name: yt-microservicecloud #
company.name: www.yt.com #
build.artifactId: $project.artifactId$ #
build.version: $project.version$ #
修改DeptController
package com.yt.springcloud.controller;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.yt.springcloud.entity.Dept;
import com.yt.springcloud.service.impl.DeptService;
@RestController//整合了responceBody+Controller
public class DeptController {
@Autowired
private DeptService service = null;
@RequestMapping(value = "/dept/get/{id}", method = RequestMethod.GET)
//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_Get")//发生异常的时候,会调用这个fallbackmethod方法,去处理
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;
}
/**
* 发生异常的时候,会调用这个方法来处理,还是返回一个dept对象,但是里面的信息是我们自定义的
* @param id
* @return
*/
public Dept processHystrix_Get(@PathVariable("id") Long id){
return new Dept().setDeptno(id).setDname("该ID：" + id + "没有没有对应的信息,[email protected]")
.setDb_source("no this database in MySQL");
}
}
实体类的链式风格异常,要安装lombok的插件
https://blog.csdn.net/yuanting_/article/details/88667206
修改主启动类DeptProvider8001-Hystrix_App并添加新注解@EnableCircuitBre
package com.yt.springcloud;
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.netflix.eureka.EnableEurekaClient;
@SpringBootApplication
@EnableEurekaClient //本服务启动后会自动注册进eureka服务中
@EnableDiscoveryClient //服务发现
@EnableCircuitBreaker//对hystrixR熔断机制的支持!!!
public class DeptProvider8001_Hystrix_App
{
public static void main(String[] args)
{
SpringApplication.run(DeptProvider8001_Hystrix_App.class, args);
}
}
测试
3个eureka先启动
主启动类DeptProvider8001_Hystrix_App
启动microservicecloud-consumer-dept-80