分布式存在的问题
服务雪崩
多个微服务之间调用的时候,假设微服务A调用微服务B和微服务C,微服务B和微服务C又调用其它的微服务,这就是所谓的“扇出”。如果扇出的链路上某个微服务的调用响应时间过长或者不可用,对微服务A的调用就会占用越来越多的系统资源,进而引起系统崩溃,所谓的“雪崩效应”.
对于高流量的应用来说,单一的后端依赖可能会导致所有服务器上的所有资源都在几秒钟内饱和。比失败更糟糕的是,这些应用程序还可能导致服务之间的延迟增加,备份队列,线程和其他系统资源紧张,导致整个系统发生更多的级联故障。这些都表示需要对故障和延迟进行隔离和管理,以便单个依赖关系的失败,不能取消整个应用程序或系统。
Hystrix是什么
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、不必要地占用,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,会进行服务的降级,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。
作用:
服务降级,服务熔断,服务限流,接近实时的监控
参看cloud-provider-8001,创建cloud-provider-hystrix-8001项目
pom文件:
<?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>cloud-parent</artifactId>
<groupId>com.el.cloud</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<groupId>com.el.cloud</groupId>
<artifactId>cloud-provider-hystrix-8001</artifactId>
<name>cloud-provider-hystrix-8001</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>
<dependencies>
<!-- hystrix -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</artifactId>
</dependency>
<!-- 引入自己定义的api通用包,可以使用Dept部门Entity -->
<dependency>
<groupId>com.el.cloud</groupId>
<artifactId>cloud-api</artifactId>
<version>${project.version}</version>
</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>
<!-- 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>
yml文件:
server:
port: 8002
mybatis:
config-location: classpath:mybatis/mybatis.cfg.xml # mybatis配置文件所在路径
type-aliases-package: com.el.consumer.cloud.entities # 所有Entity别名类所在包
mapper-locations:
- classpath:mybatis/mapper/**/*.xml # mapper映射文件
spring:
application:
name: cloud-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://192.168.137.131:3306/cloudDB01 # 数据库名称
username: root
password: root
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/
instance:
instance-id: cloud-provider-hystrix-dept-8001
prefer-ip-address: true #访问路径可以显示IP地址
info:
app.name: elitesland-cloud
company.name: www.baidu.com
build.artifactId: $project.artifactId$
build.version: $project.version$
修改DeptController:
package com.el.cloud.controller;
import com.el.cloud.service.DeptService;
import com.el.consumer.cloud.entities.Dept;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;
/**
* @Auther: roman.zhang
* @Date: 2019/3/19 10:55
* @Version:V1.0
* @Description:DeptController
*/
//@Controller
@RestController
public class DeptController {
@Autowired
private DeptService service;
@RequestMapping(value="/dept/get/{id}",method=RequestMethod.GET)
@HystrixCommand(fallbackMethod = "processHystrix_Get")
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_Get(@PathVariable("id") Long id){
return new Dept().setDeptno(id).setDname("该ID:"+id+"没有没有对应的信息,null--@HystrixCommand")
.setDb_source("no this database in MySQL");
}
}
修改主启动类DeptProvider_hystrix_8001_App
package com.el.cloud;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
/**
* Hello world!
*
*/
@SpringBootApplication
@EnableEurekaClient //本服务启动后会自动注册进eureka服务中
@EnableCircuitBreaker//对hystrixR熔断机制的支持
public class DeptProvider_hystrix_8001_App
{
public static void main( String[] args )
{
SpringApplication.run(DeptProvider_hystrix_8001_App.class,args);
}
}
测试:
1.3个eureka先启动
2.启动DeptProvider_hystrix_8001_App
2.启动消费者
总结:
如果对应的ID:112,数据库里面没有这个记录,我们报错后统一返回。
服务降级
整体资源快不够了,忍痛将某些服务先关掉,待渡过难关,再开启回来。服务降级处理是在客户端实现完成的,与服务端没有关系
步骤:
1.修改cloud-api项目:根据已经有的DeptClientService接口新建一个实现了FallbackFactory接口的类DeptClientServiceFallbackFactory
package com.el.consumer.cloud.service.impl;
import com.el.consumer.cloud.entities.Dept;
import com.el.consumer.cloud.service.DeptClientService;
import feign.hystrix.FallbackFactory;
import org.springframework.stereotype.Component;
import java.util.List;
/**
* @Auther: roman.zhang
* @Date: 2019/3/20 9:48
* @Version:V1.0
* @Description:DeptClientServiceFallbackFactory
*/
@Component
public class DeptClientServiceFallbackFactory implements FallbackFactory<DeptClientService> {
@Override
public DeptClientService create(Throwable throwable)
{
return new DeptClientService() {
@Override
public Dept get(long id)
{
return new Dept().setDeptno(id)
.setDname("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")
.setDb_source("no this database in MySQL");
}
@Override
public List<Dept> list()
{
return null;
}
@Override
public boolean add(Dept dept)
{
return false;
}
};
}
}
修改cloud-api工程,DeptClientService接口在注解@FeignClient中添加fallbackFactory属性值
package com.el.consumer.cloud.service;
import com.el.consumer.cloud.entities.Dept;
import com.el.consumer.cloud.service.impl.DeptClientServiceFallbackFactory;
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;
/**
* @Auther: roman.zhang
* @Date: 2019/3/19 16:43
* @Version:V1.0
* @Description:DeptClientService
*/
//@FeignClient(value = "cloud-dept")
@FeignClient(value = "cloud-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);
}
修改cloud-cpnsumer-feign的yml文件
server:
port: 80
feign:
hystrix:
enabled: true
eureka:
client:
register-with-eureka: false
service-url:
defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/
测试:
1.3个eureka先启动
2.启动DeptProvider8001_App
3.启动消费者
4.正常访问
5.关闭服务提供者
6.
总结:
此时服务端provider已经down了,但是我们做了服务降级处理,让客户端在服务端不可用时也会获得提示信息而不会挂起耗死服务器
服务监控hystrixDashboard
除了隔离依赖服务的调用以外,Hystrix还提供了准实时的调用监控(Hystrix Dashboard),Hystrix会持续地记录所有通过Hystrix发起的请求的执行信息,并以统计报表和图形的形式展示给用户,包括每秒执行多少请求多少成功,多少失败等。Netflix通过hystrix-metrics-event-stream项目实现了对以上指标的监控。Spring Cloud也提供了Hystrix Dashboard的整合,对监控内容转化成可视化界面。
新建cloud-consumer-hystrixdashboard
pom文件
<?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>cloud-parent</artifactId>
<groupId>com.el.cloud</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<groupId>com.el.cloud</groupId>
<artifactId>cloud-consumer-hystrix-dashboard</artifactId>
<dependencies>
<dependency>
<groupId>com.el.cloud</groupId>
<artifactId>cloud-api</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</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>
<!-- Ribbon相关 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-ribbon</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-config</artifactId>
</dependency>
<!-- feign相关 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
<!-- hystrix和 hystrix-dashboard相关-->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
</dependency>
</dependencies>
</project>
yml文件
server:
port: 9001
创建启动类:
package com.el.dashboard;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
/**
* @Auther: roman.zhang
* @Date: 2019/3/20 10:31
* @Version:V1.0
* @Description:DeptConsumer_DashBoard_App
*/
@SpringBootApplication
@EnableHystrixDashboard
public class DeptConsumer_DashBoard_App {
public static void main(String[] args)
{
SpringApplication.run(DeptConsumer_DashBoard_App.class,args);
}
}
服务提供者需添加:
<!-- actuator监控信息完善 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
启动相应的,注册服务者,服务提供者,消费者,