13.Dubbo服务降级与整合Hystrix实现断路器

今天药忘吃喽~ 2022-05-14 07:10 151阅读 0赞

# 一、服务降级 #

**什么是服务降级？**

**当服务器压力剧增的情况下，根据实际业务情况及流量，对一些服务和页面有策略的不处理或换种简单的方式处理，从而释放服务器资源以保证核心交易正常运作或高效运作。**

通过Dubbo-Admin控制台进行操作

可以通过服务降级功能临时屏蔽某个出错的非关键服务，并定义降级后的返回策略。

向注册中心写入动态配置覆盖规则：

<table> 
 <tbody> 
  <tr> 
   <td style="width:453.1pt;"> <p style="margin-left:0cm;">RegistryFactory registryFactory = ExtensionLoader.getExtensionLoader(RegistryFactory.class).getAdaptiveExtension();</p> <p style="margin-left:0cm;">Registry registry = registryFactory.getRegistry(URL.valueOf("zookeeper://10.20.153.10:2181"));</p> <p style="margin-left:0cm;">registry.register(URL.valueOf("override://0.0.0.0/com.foo.BarService?category=configurators&amp;dynamic=false&amp;application=foo&amp;mock=force:return+null"));</p> </td> 
  </tr> 
 </tbody> 
</table>

其中：

1.  mock=force:return+null 表示消费方对该服务的方法调用都直接返回 null 值，不发起远程调用。用来屏蔽不重要服务不可用时对调用方的影响。
2.  还可以改为 mock=fail:return+null 表示消费方对该服务的方法调用在失败后，再返回 null 值，不抛异常。用来容忍不重要服务不稳定时对调用方的影响。

# 二、整合hystrix #

Hystrix 旨在通过控制那些访问远程系统、服务和第三方库的节点，从而对延迟和故障提供更强大的容错能力。Hystrix具备拥有回退机制和断路器功能的线程和信号隔离，请求缓存和请求打包，以及监控和配置等功能。

演示代码，只显示重要部分，全部代码文章末尾有代码下载地址

## 2.1新建Maven项目 ##

![70][]

## 2.2dubbo-spring-boot-hystrix  ##

## 2.2.1pom.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>
    	<groupId>org.niugang</groupId>
    	<artifactId>dubbo-spring-boot-hystrix</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    	<packaging>pom</packaging>
    	
    	<dependencyManagement>
    		<dependencies>
    			
    			<dependency>
    				<groupId>org.springframework.boot</groupId>
    				<artifactId>spring-boot-dependencies</artifactId>
    				<version>2.0.3.RELEASE</version>
    				<type>pom</type>
    				<scope>import</scope>
    			</dependency>
    			
    			<dependency>
    				<groupId>org.springframework.cloud</groupId>
    				<artifactId>spring-cloud-dependencies</artifactId>
    				<version>Finchley.SR1</version>
    				<type>pom</type>
    				<scope>import</scope>
    			</dependency>
    		</dependencies>
    	</dependencyManagement>
    	<modules>
    		<module>dubbo-spring-boot-hystrix-api</module>
    		<module>dubbo-spring-boot-hystrix-provider</module>
    		<module>dubbo-spring-boot-hystrix-consumer</module>
    	</modules>
    </project>

## 2.3dubbo-spring-boot-hystrix-provider ##

### 2.3.1pom.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>org.niugang</groupId>
    		<artifactId>dubbo-spring-boot-hystrix</artifactId>
    		<version>0.0.1-SNAPSHOT</version>
    	</parent>
    	<artifactId>dubbo-spring-boot-hystrix-provider</artifactId>
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>
    		
    		<dependency>
    			<groupId>com.alibaba.boot</groupId>
    			<artifactId>dubbo-spring-boot-starter</artifactId>
    			<version>0.2.0</version>
    		</dependency>
    
    		<dependency>
    			<groupId>org.niugang</groupId>
    			<artifactId>dubbo-spring-boot-hystrix-api</artifactId>
    			<version>0.0.1-SNAPSHOT</version>
    		</dependency>
    
    		
    		<dependency>
    			<groupId>redis.clients</groupId>
    			<artifactId>jedis</artifactId>
    		</dependency>
    		
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    		</dependency>
    	</dependencies>
    </project>

### 2.3.2 对外暴露RPCs实现类 ###

package org.niugang.service;
    
    import java.util.Random;
    
    import org.springframework.stereotype.Component;
    import com.alibaba.dubbo.config.annotation.Service;
    import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
    import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;
    
    /**
     * 
     * @ClassName: DefaultDemoService
     * @Description:对外暴露接口实现类
     * @author: niugang
     * @date: 2018年8月17日 下午7:50:47
     * @Copyright: 863263957@qq.com. All rights reserved.
     *
     */
    // demo.service.version 在application.properties中配置过了
    @Service // dubbo注解
    @Component
    @Service // dubbo注解
    @Component
    public class DefaultServiceImpl implements DefaultApiService {
    
    	@HystrixCommand(commandProperties = {
    			@HystrixProperty(name = "circuitBreaker.requestVolumeThreshold", value = "10"),
    			@HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "2000") })
    	public String defaultMethod(String str) {
    		/*
    		 * Hystrix超时配置的为2s,当实现类睡眠超过2s，服务调用者将执行服务降级函数
    		 */
    		int nextInt = new Random().nextInt(4000);
    		System.out.println("sleep " + nextInt + "ms");
    		try {
    			Thread.sleep(nextInt);
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    		return "HELLO  " + str + " from Dubbo Spring Boot";
    	}
    
    }

## 2.4 dubbo-spring-boot-hystrix-consumer ##

### 2.4.1 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>org.niugang</groupId>
    		<artifactId>dubbo-spring-boot-hystrix</artifactId>
    		<version>0.0.1-SNAPSHOT</version>
    	</parent>
    	<artifactId>dubbo-spring-boot-hystrix-consumer</artifactId>
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>com.alibaba.boot</groupId>
    			<artifactId>dubbo-spring-boot-starter</artifactId>
    			<version>0.2.0</version>
    		</dependency>
    		
    		<dependency>
    			<groupId>redis.clients</groupId>
    			<artifactId>jedis</artifactId>
    		</dependency>
    		
    		<dependency>
    			<groupId>org.niugang</groupId>
    			<artifactId>dubbo-spring-boot-hystrix-api</artifactId>
    			<version>0.0.1-SNAPSHOT</version>
    		</dependency>
    		
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    		</dependency>
    	</dependencies>
    </project>

### 2.4.2调用服务提供者 ###

/**
    	 * 引入服务提供者
    	 */
    	// com.alibaba.dubbo.config.annotation.Reference
    	@Reference
    	private DefaultApiService demoService;
    
    	@RequestMapping("/sayHello")
    	@HystrixCommand(fallbackMethod = "failBackMethod")
    	public String sayHello(@RequestParam String name) {
    		return demoService.defaultMethod(name);
    	}
    
    	/**
    	 * 服务降级
    	 * @param name
    	 * @return
    	 */
    	public String failBackMethod(String name) {
    		return "service request fail";
    	}

## 5.结果 ##

### 5.1成功调用 ###

![70 1][]

### 5.2失败调用 ###

![70 2][]

## 6.源码 ##

[https://gitee.com/niugangxy/dubbo][https_gitee.com_niugangxy_dubbo]

##    ##

**微信公众号**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25pdWdhbmcwOTIw_size_16_color_FFFFFF_t_70][]

[70]: /images/20220514/24c2da57a4ff4e1f93c18a50f2bcb0e1.png
[70 1]: /images/20220514/3ed43dc0ab2e40c683f21ff3994b0bff.png
[70 2]: /images/20220514/6165fdc7fcf74cf9901d0d0bd5db5796.png
[https_gitee.com_niugangxy_dubbo]: https://gitee.com/niugangxy/dubbo
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25pdWdhbmcwOTIw_size_16_color_FFFFFF_t_70]: /images/20220514/5fa1dda95a1a47599c3b06b4cdf8fd57.png