1.什么是注册中心

注册中心主要有三种角色：

• 服务提供者（RPC Server）：在启动时，向 Registry 注册自身服务，并向 Registry 定期发送心跳汇报存活状态。

• 服务消费者（RPC Client）：在启动时，向 Registry 订阅服务，把 Registry 返回的服务节点列表缓存在本地内存中，并与 RPC Sever 建立连接。

• 服务注册中心（Registry）：用于保存 RPC Server 的注册信息，当 RPC Server 节点发生变更时，Registry 会同步变更，RPC Client 感知后会刷新本地 内存中缓存的服务节点列表。

2.框架版本

spring boot：2.7.13

spring cloud：2021.0.1

3.xxx-discovery-etcd

支持etcd作为服务的注册中心，在微服务中使用

3.1.使用

pom.xml中引入依赖

<dependency><groupId>x.xx.xxx</groupId><artifactId>xxx-discovery-etcd</artifactId>
</dependency>

application.yml中配置

spring:application:name: etcd-provider-examplexxx:discovery:etcd:server-addr: http://192.168.184.133:2379instance-name: provider1                

启动主类增加注解@EnableDiscoveryClient

4.Spring Cloud和xxx-etcd-discovery的结合

4.1.etcd-provider-demo

pom.xml

<?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"><modelVersion>4.0.0</modelVersion>
​<groupId>org.example</groupId><artifactId>etcd-provider-demo</artifactId><version>1.0-SNAPSHOT</version>
​<dependencies><dependency><groupId>x.xx.xxx</groupId><artifactId>xxx-discovery-etcd</artifactId></dependency>
​<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>
​<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-bootstrap</artifactId></dependency>
​</dependencies>
​
</project>

bootstrap.yml

server:port: 18082
spring:application:name: etcd-provider-example
​
xxx:discovery:etcd:server-addr: http://192.168.184.133:2379instance-name: provider1
​
logging:level:root: DEBUGio:grpc:netty:NettyClientHandler: INFO
​org:springframework:boot:autoconfigure: INFO

EtcdProviderExampleApplication

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
​
@SpringBootApplication
@EnableDiscoveryClient
public class EtcdProviderExampleApplication {
​public static void main(String[] args) {SpringApplication.run(EtcdProviderExampleApplication.class, args);}
}

EchoController

package x.xx.xxx.etcd.demo;
​
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
​
@RestController
public class EchoController {@RequestMapping(value = "/echo/{string}", method = RequestMethod.GET)public String echo(@PathVariable String string) {return System.currentTimeMillis() + "--Hello Etcd Discovery " + string;}
}

4.2.etcd-consumer-demo

pom.xml

<?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"><modelVersion>4.0.0</modelVersion>
​<groupId>org.example</groupId><artifactId>etcd-consumer-demo</artifactId><version>1.0-SNAPSHOT</version>
​<dependencies><dependency><groupId>x.xx.xxx</groupId><artifactId>xxx-discovery-etcd</artifactId></dependency>
​<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>
​<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-bootstrap</artifactId></dependency>
​<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-webflux</artifactId></dependency>
​</dependencies>
​
</project>

bootstrap.yml

server:port: 18081
​
spring:application:name: etcd-consumer-example
​
xxx:discovery:etcd:server-addr: http://192.168.184.133:2379instance-name: consumer1logging:level:root: DEBUGio:grpc:netty:NettyClientHandler: INFO
​org:springframework:boot:autoconfigure: INFO

EtcdConsumerExampleApplication

package x.xx.xxx.etcd.demo;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.reactive.function.client.WebClient;@SpringBootApplication
@EnableDiscoveryClient
public class EtcdConsumerExampleApplication {public static void main(String[] args) {SpringApplication.run(EtcdConsumerExampleApplication.class, args);}@LoadBalanced@Beanpublic RestTemplate restTemplate() {return new RestTemplate();}@Bean@LoadBalancedpublic WebClient.Builder loadBalancedWebClientBuilder() {return WebClient.builder();}
}

TestController

package x.xx.xxx.etcd.demo;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.reactive.function.client.WebClient;@RestController
public class TestController {private final RestTemplate restTemplate;@Autowiredpublic TestController(RestTemplate restTemplate) {this.restTemplate = restTemplate;}@RequestMapping(value = "/echo/{str}", method = RequestMethod.GET)public String echo(@PathVariable String str) {return restTemplate.getForObject("http://etcd-provider-example/echo/" + str, String.class);}@Autowiredprivate WebClient.Builder webClientBuilder;@RequestMapping(value = "/echo/webClient/{str}", method = RequestMethod.GET)public String echoWebClient(@PathVariable String str) {WebClient webClient = webClientBuilder.build();webClient.get().uri("http://etcd-provider-example/echo/" + str).retrieve().bodyToMono(String.class).subscribe(response -> {System.err.println("控制台响应结果:" + response);});return System.currentTimeMillis() + "--echoWebClient--" + str + "--请查看控制台是否执行成功!";}}

4.3.启动主程序

EtcdProviderExampleApplication

EtcdConsumerExampleApplication

通过ETCD Manager查看，如下表示注册成功

请求etcd-consumer-demo中接口，查看服务发现功能，更改测试接口，可查看TestController

http://localhost:18081/echo/6666

浏览器返回如下信息表示服务发现成功

1705978409084--Hello Etcd Discovery 6666

5.xxx-etcd-discovery详解

5.1.可配置属性

5.2.存储到etcd的格式

5.3.监控ectd服务端事件,并发送事件

5.4.启动全量查所有服务列表并缓存