基于Spring Cloud搭建分布式配置中心

古城微笑少年丶 2023-09-28 22:05 9阅读 0赞

## 一.Spring Cloud简介 ##

先来看看官网对spring cloud的定义：

> Spring Cloud offers a simple and accessible programming model to the most common distributed system patterns, helping developers build resilient, reliable, and coordinated applications.

再来看看整个spring cloud的architecture  
![这里写图片描述][70]  
可以看出spring cloud的意义在于推出了一个基于spring的全链路方案，包括gateway，tracing，microservices，configCenter，service registry等等，中小型公司在基于spring cloud和springBoot的基础上进行搭建系统的话，只要稍作定制化便能很快的搭建起一个能支撑一定量qps和数据的系统

## 二.基于Spring Cloud搭建分布式配置中心 ##

（1）首先简单浏览一下我们要搭建的config center的architecture:  
![这里写图片描述][70 1]  
1.git repository作为配置的存储地  
2.Config Server设置两台作为高可用  
3.eureka server设置两台注册中心作为高可用  
4.config client作为客户端获取配置

（2）下面看看关键代码：

### 1.配置eureka注册中心 ###

EurekaServiceApplication：

package com.andrew.eureka.server;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
    
    @EnableEurekaServer
    @SpringBootApplication
    public class EurekaServiceApplication {
        public static void main(String[] args) {
            SpringApplication.run(EurekaServiceApplication.class, args);
        }
    }

application-peer1.properties配置：

server.port=8761
    
    eureka.client.register-with-eureka=true
    eureka.client.fetch-registry=true
    eureka.client.service-url.defaultZone=http://peer2:8762/eureka
    eureka.instance.appname=eureka-server
    eureka.instance.hostname=peer1
    
    logging.level.com.netflix.eureka=OFF
    logging.level.com.netflix.discovery=OFF

application-peer2.properties配置：

server.port=8762
    
    eureka.client.register-with-eureka=true
    eureka.client.fetch-registry=true
    eureka.client.service-url.defaultZone=http://peer1:8761/eureka
    eureka.instance.appname=eureka-server
    eureka.instance.hostname=peer2
    
    logging.level.com.netflix.eureka=OFF
    logging.level.com.netflix.discovery=OFF

通过mvn clean install命令打包成jar之后，跑命令

java -jar eureka-service-0.0.1-SNAPSHOT.jar --spring.profiles.active=peer1 
    java -jar eureka-service-0.0.1-SNAPSHOT.jar --spring.profiles.active=peer2

输入[http://localhost:8761/][http_localhost_8761]之后，可以看到  
![这里写图片描述][70 2]

里面的available-replicas可以看到拥有peer2这个备份service

### 2.配置config server ###

ConfigServerApplication：

package com.andrew.config.server;
    
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.builder.SpringApplicationBuilder;
    import org.springframework.cloud.config.server.EnableConfigServer;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    
    @EnableConfigServer
    @SpringBootApplication
    @EnableEurekaClient
    public class ConfigServerApplication {
        public static void main(String[] args) {
            new SpringApplicationBuilder(ConfigServerApplication.class).run(args);
        }
    }

每个eureka client都必须有@EnableEurekaClient这个注解，每个config server必须有@EnableConfigServer这个注解

application.yml配置文件:

spring:
      application:
        name: config-server
      cloud:
        config:
          server:
            git:
              uri: F:\public-projects\spring-cloud\spring-cloud-config\gs-centralized-configuration-master\config
    
    eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka,http://localhost:8762/eureka

注意spring cloud使用git做配置的存储仓库，这里我是用了本地的git仓库，一般来说是通过远程仓库作为配置的存储  
跑下面两个命令起两个config server：

java -jar config-server-0.0.1-SNAPSHOT.jar --server.port=8888
    java -jar config-server-0.0.1-SNAPSHOT.jar --server.port=8889

![这里写图片描述][70 3]

可以看到两个config server已经注册到eureka server上了

### 3.配置config client ###

package com.andrew.config.client;
    
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.builder.SpringApplicationBuilder;
    import org.springframework.cloud.context.config.annotation.RefreshScope;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @EnableEurekaClient
    @SpringBootApplication
    public class ConfigClientApplication {
    
        public static void main(String[] args) {
            new SpringApplicationBuilder(ConfigClientApplication.class).run(args);
        }
    }
    
    @RefreshScope
    @RestController
    class MessageRestController {
    
        @Value("${message:Hello default}")
        private String message;
    
        @RequestMapping("/message")
        String getMessage() {
            return this.message;
        }
    }

@RefreshScope是因为config client只会在第一次初始化bean的时候获取一次配置，后面如果需要更新的话，需要设置这个注解在controller上面，并且引入spring actuator的包，通过发送post请求来更新bean里面的值  
@Value注解表示要获取的是key为message的值，默认值是Hello default

配置application.properties：

management.endpoints.web.exposure.include=*
    
    spring.application.name=config-client
    spring.cloud.config.discovery.enabled=true
    spring.cloud.config.discovery.serviceId=config-server
    eureka.client.service-url.defaultZone=http://localhost:8761/eureka,http://localhost:8762/eureka

spring.cloud.config.discovery.enabled=true能够让config client自动去发现config server  
spring.cloud.config.discovery.serviceId=config-server是根据configServer在配置文件里面的applicationName设置，configClient根据serviceId去探测configServer

> PS:每个configClient会在第一次初始化之后从eureka service获取到注册在上面的服务器信息，后面即使eureka service down掉，仍然能够根据本地缓存去访问到config server

运行下面命令启动config-client:

java -jar config-client-0.0.1-SNAPSHOT.jar --server.port=8081

![这里写图片描述][70 4]  
可以看到config-client已经注册上去

### 4.Test Application ###

applicationContext.properties文件:

hello=helloWorld
    message = congratulation success

在浏览器输入：[http://localhost:8081/message][http_localhost_8081_message] 可以看到结果是：

![这里写图片描述][70 5]

当我们修改文件内容为

hello=helloWorld
    message = haha we change the value

git commit之后，通过postman发送post请求到[http://localhost:8081/actuator/refresh][http_localhost_8081_actuator_refresh]，再去调用[http://localhost:8081/message][http_localhost_8081_message] ，可以看到新的配置值：  
![这里写图片描述][70 6]  
通过这我们就可以成功获取到更新后的配置

### 5.优点和缺点 ###

优点：  
1.eureka作为注册中心，不像zk需要选举master，eureka是peer形式的，那么即使出现网络变化导致注册中心实例少于一定数量，eureka也可以保证一直的提供服务  
2.当网络变化的时候，eureka会有一个Self Preservation Mode的机制，如果15%的注册实例在短时间内出现down的情况（通过heartbeat确认），那么eureka不会移除实例的注册信息，而是等到网络恢复之后仍然以这个实例信息去提供给调用方

> 具体可以通过：[https://github.com/Netflix/eureka/wiki/Server-Self-Preservation-Mode][https_github.com_Netflix_eureka_wiki_Server-Self-Preservation-Mode]这里了解

缺点：  
1.需要自己定制化一个流程审批界面，没有一个完整的权限控制流程  
2.缺少一个界面去维护管理配置  
3.不像zk是使用观察者模式，每个client可以去监听配置的变化，每次更新都需要主动去发送一次post请求更新或者必须通过git webhook加上消息队列做热更新，需要另外做一个封装的api使得更新配置对上层无感知  
4.全程都是用http去实现，不如zk通过tcp长连接来的更有效率  
5.基于git仓库保存配置，从文件系统在io上性能没有从mysql读快，并且可以在文件系统前加入redis之类的缓存机制提供更强的性能

### 6.附记 ###

demo代码：[https://github.com/AndrewHuangMiao/spring-cloud-config-eureka][https_github.com_AndrewHuangMiao_spring-cloud-config-eureka]  
业界基于springboot和springcloud做了定制化之后的使用：[https://github.com/ctripcorp/apollo/][https_github.com_ctripcorp_apollo]

### 7.参考： ###

[https://spring.io/guides/gs/service-registration-and-discovery/][https_spring.io_guides_gs_service-registration-and-discovery]  
[https://spring.io/guides/gs/centralized-configuration/][https_spring.io_guides_gs_centralized-configuration]  
[https://www.aliyun.com/jiaocheng/820688.html][https_www.aliyun.com_jiaocheng_820688.html]

written by:黄文岳

[70]: https://img-blog.csdn.net/2018072013484393?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3ZpcHNob3BfZmluX2Rldg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 1]: https://img-blog.csdn.net/20180720140350615?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3ZpcHNob3BfZmluX2Rldg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[http_localhost_8761]: http://localhost:8761/
[70 2]: https://img-blog.csdn.net/20180720151649485?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3ZpcHNob3BfZmluX2Rldg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 3]: https://img-blog.csdn.net/20180720154216792?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3ZpcHNob3BfZmluX2Rldg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 4]: https://img-blog.csdn.net/20180720155514683?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3ZpcHNob3BfZmluX2Rldg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[http_localhost_8081_message]: http://localhost:8081/message
[70 5]: https://img-blog.csdn.net/20180720160915239?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3ZpcHNob3BfZmluX2Rldg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[http_localhost_8081_actuator_refresh]: http://localhost:8081/actuator/refresh
[70 6]: https://img-blog.csdn.net/20180720164554203?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3ZpcHNob3BfZmluX2Rldg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[https_github.com_Netflix_eureka_wiki_Server-Self-Preservation-Mode]: https://github.com/Netflix/eureka/wiki/Server-Self-Preservation-Mode
[https_github.com_AndrewHuangMiao_spring-cloud-config-eureka]: https://github.com/AndrewHuangMiao/spring-cloud-config-eureka
[https_github.com_ctripcorp_apollo]: https://github.com/ctripcorp/apollo/
[https_spring.io_guides_gs_service-registration-and-discovery]: https://spring.io/guides/gs/service-registration-and-discovery/
[https_spring.io_guides_gs_centralized-configuration]: https://spring.io/guides/gs/centralized-configuration/
[https_www.aliyun.com_jiaocheng_820688.html]: https://www.aliyun.com/jiaocheng/820688.html