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SpringCloud服務(wù)注冊中心雙節(jié)點集群(Eureka集群)
作者：xcbeyond
瘋狂源自夢想，技術(shù)成就輝煌！微信公眾號：《程序猿技術(shù)大咖》號主，專注后端開發(fā)多年，擁有豐富的研發(fā)經(jīng)驗，樂于技術(shù)輸出、分享，現(xiàn)階段從事微服務(wù)架構(gòu)項目的研發(fā)工作，涉及架構(gòu)設(shè)計、技術(shù)選型、業(yè)務(wù)研發(fā)等工作。對于Java、微服務(wù)、數(shù)據(jù)庫、Docker有深入了解，并有大量的調(diào)優(yōu)經(jīng)驗。
0、前言
最近在進行重構(gòu)一個新項目，為了后續(xù)更好的落地，適應(yīng)于日新月異的技術(shù)更新，進行了各方的技術(shù)選型及技術(shù)預(yù)研，最終選型基于微服務(wù)架構(gòu)體系進行開發(fā)重構(gòu)。項目構(gòu)建前最重要的一步就是要想清楚，整體的部署架構(gòu)、高可用性(HA)等等，做好前期的部署架構(gòu)技術(shù)調(diào)研，確定最終方案。
在微服務(wù)架構(gòu)體系中，核心技術(shù)便是Spring Cloud，通過登錄官網(wǎng)查看SpringCloud已經(jīng)集成了好多優(yōu)質(zhì)的項目，供我們使用借鑒。而SpringCloud Eureka是云端服務(wù)發(fā)現(xiàn)，一個基于 REST 的服務(wù)，用于定位服務(wù)，以實現(xiàn)云端中間層服務(wù)發(fā)現(xiàn)和故障轉(zhuǎn)移，并且支持集群部署。因此，本次部署架構(gòu)技術(shù)方案選型打算采用Eureka集群。
(關(guān)于Eureka服務(wù)注冊與發(fā)現(xiàn)請查看上一章節(jié)內(nèi)容【SpringCloud系列】一、SpringCloud服務(wù)注冊與發(fā)現(xiàn)(Eureka))
本文將闡述SpringCloud服務(wù)注冊中心雙節(jié)點集群(Eureka集群)方案及集群demo。
1、Eureka集群概述
1.1 基本原理
如上圖，是Eureka集群配置圖。
- 不同節(jié)點的Eureka Server通過Replicate(復(fù)制)進行數(shù)據(jù)同步
- Application Service為服務(wù)提供者
- Application Client為服務(wù)消費者
- Make Remote Call完成一次服務(wù)調(diào)用
服務(wù)啟動后向Eureka注冊，Eureka Server會將注冊信息向其他Eureka Server進行同步，當服務(wù)消費者要調(diào)用服務(wù)提供者，則向服務(wù)注冊中心獲取服務(wù)提供者地址(即：服務(wù)應(yīng)用名，spring.application.name參數(shù)配置)，然后會將服務(wù)提供者地址緩存在本地，下次再調(diào)用時，則直接從本地緩存中取，完成一次調(diào)用。
當服務(wù)注冊中心Eureka Server檢測到服務(wù)提供者因為宕機、網(wǎng)絡(luò)原因不可用時，則在服務(wù)注冊中心將服務(wù)置為DOWN狀態(tài)，并把當前服務(wù)提供者狀態(tài)向訂閱者發(fā)布，訂閱過的服務(wù)消費者更新本地緩存。
服務(wù)提供者在啟動后，周期性（默認30秒）向Eureka Server發(fā)送心跳，以證明當前服務(wù)是可用狀態(tài)。Eureka Server在一定的時間（默認90秒）未收到客戶端的心跳，則認為服務(wù)宕機，注銷該實例。
1.2 Eureka自我保護機制
在默認配置中，Eureka Server在默認90s沒有得到客戶端的心跳，則注銷該實例，但是往往因為微服務(wù)跨進程調(diào)用，網(wǎng)絡(luò)通信往往會面臨著各種問題，比如微服務(wù)狀態(tài)正常，但是因為網(wǎng)絡(luò)分區(qū)故障時，Eureka Server注銷服務(wù)實例則會讓大部分微服務(wù)不可用，這很危險，因為服務(wù)明明沒有問題。
為了解決這個問題，Eureka 有自我保護機制，通過在Eureka Server配置如下參數(shù)，可啟動保護機制。
eureka.server.enable-self-preservation=true
它的原理是，當Eureka Server節(jié)點在短時間內(nèi)丟失過多的客戶端時（可能發(fā)送了網(wǎng)絡(luò)故障），那么這個節(jié)點將進入自我保護模式，不再注銷任何微服務(wù)，當網(wǎng)絡(luò)故障回復(fù)后，該節(jié)點會自動退出自我保護模式。
1.3 Eureka高可用集群
理論上來講，因為服務(wù)消費者本地緩存了服務(wù)提供者的地址，即使Eureka Server宕機，也不會影響服務(wù)之間的調(diào)用，但是一旦新服務(wù)上線，已經(jīng)在緩存在本地的服務(wù)提供者不可用了，服務(wù)消費者也無法知道，所以保證Eureka Server的高可用還是很有必要的。
在分布式系統(tǒng)中，任何的地方存在單點，整個體系就不是高可用的，Eureka 也一樣，在上面的架構(gòu)圖中Eureka Server不是以單點存在的，而是以集群的方式對外提供服務(wù)。
2、Eureka雙中心節(jié)點集群
本節(jié)以具體示例說明Eureka集群及配置。
2.1 創(chuàng)建Eureka Server
（1）新建springCloudEurekaCluster項目作為Eureka Server集群項目：
pom.xml如下：
<?xml version="1.0"?>
<project
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<modelVersion>4.0.0</modelVersion>
<groupId>com.xcbeyond.springcloud</groupId>
<artifactId>springCloudEurekaCluster</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>springCloudEurekaCluster</name>
<url>http://maven.apache.org</url>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.0.RELEASE</version>
<relativePath/>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</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>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
<version>2.0.0.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
<version>2.0.0.RELEASE</version>
</dependency>
</dependencies>
<description>Eureka集群</description>
</project>
（2）配置application.properties。
在Eureka Server集群時，需要部署多個節(jié)點，則需要同一個項目，使用不同的配置。因此，在本例中使用springCloudEurekaCluster一個項目通過不同的啟動參數(shù)來啟動占用不同端口的兩個Server服務(wù)，來模擬Eureka集群。則使用下面三個*.properties配置文件：
application.properties
application-eureka-server1.properties
application-eureka-server2.properties
application.properties
#應(yīng)用名
spring.application.name=eureka-cluster
application-eureka-server1.properties
##eureka-server1節(jié)點配置，配置參數(shù)--spring.profiles.active=eureka-server1來啟動該環(huán)境
spring.profiles=eureka-server1
server.port=8761
eureka.instance.hostname=eureka-server1
eureka.client.serviceUrl.defaultZone=http://eureka-server2:8762/eureka/
application-eureka-server2.properties
##eureka-server2節(jié)點配置，配置參數(shù)--spring.profiles.active=eureka-server2來啟動該環(huán)境
spring.profiles=eureka-server2
server.port=8762
eureka.instance.hostname=eureka-server2
eureka.client.serviceUrl.defaultZone=http://eureka-server1:8761/eureka/
application-eureka-server1.properties、application-eureka-server2.properties配置文件設(shè)置了不同的端口(server.port)，重點是參數(shù)eureka.client.serviceUrl.defaultZone，分別配置對方的地址作為Eureka Client進行相互注冊。由于采用了參數(shù)配置eureka.instance.hostname及http://eureka-server1的寫法，則需要在進行hosts的配置，window在C:\Windows\System32\drivers\etc\hosts，Linux是在/etc/host，此處，以我windows本機說明，在hosts文件中最近如下配置：
127.0.0.1 eureka-server1
127.0.0.1 eureka-server2
（3）新建啟動類。
com.xcbeyond.springcloud.eurekacluster.EurekaClusterApplication.java
package com.xcbeyond.springcloud.eurekacluster;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
/**
* Eureka集群啟動類
* @author xcbeyond
* 2018年8月7日上午10:34:01
*/
@SpringBootApplication
//開啟對EurekaServer的支持，即：作為Eureka服務(wù)端
@EnableEurekaServer
//開啟作為Eureka Server的客戶端的支持
@EnableDiscoveryClient
public class EurekaClusterApplication {
public static void main(String[] args) {
SpringApplication.run(EurekaClusterApplication.class, args);
}
}
重點添加@EnableEurekaServer注解，開啟對EurekaServer的支持，即：作為Eureka服務(wù)端。
項目源碼：https://download.csdn.net/download/xcbeyond/10592831
2.2.Eureka集群啟動及驗證
2.2.1 集群啟動
在創(chuàng)建Eureka server項目時，創(chuàng)建了兩個properties配置文件，作為集群不同的節(jié)點配置文件，在啟動項目時，只需指定啟動參數(shù)--spring.profiles.active=eureka-server1來指定對應(yīng)配置環(huán)境，運行啟動類即可。Eclipse IDE開發(fā)環(huán)境下，配置啟動參數(shù)方式如下：
在啟動第一個節(jié)點eureka-server1過程中，會持續(xù)出現(xiàn)如下錯誤信息：
2018-08-09 10:29:25.225 ERROR 7964 --- [nfoReplicator-0] c.n.d.s.t.d.RedirectingEurekaHttpClient : Request execution error
com.sun.jersey.api.client.ClientHandlerException: java.net.ConnectException: Connection refused: connect
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187) ~[jersey-apache-client4-1.19.1.jar:1.19.1]
at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123) ~[jersey-client-1.19.1.jar:1.19.1]
at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27) ~[eureka-client-1.9.2.jar:1.9.2]
at com.sun.jersey.api.client.Client.handle(Client.java:652) ~[jersey-client-1.19.1.jar:1.19.1]
at com.sun.jersey.api.client.WebResource.handle(WebResource.java:682) ~[jersey-client-1.19.1.jar:1.19.1]
at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74) ~[jersey-client-1.19.1.jar:1.19.1]
at com.sun.jersey.api.client.WebResource$Builder.post(WebResource.java:570) ~[jersey-client-1.19.1.jar:1.19.1]
at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.register(AbstractJerseyEurekaHttpClient.java:56) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.MetricsCollectingEurekaHttpClient.execute(MetricsCollectingEurekaHttpClient.java:73) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.executeOnNewServer(RedirectingEurekaHttpClient.java:118) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.execute(RedirectingEurekaHttpClient.java:79) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:120) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:829) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.9.2.jar:1.9.2]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_121]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_121]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_121]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_121]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_121]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_121]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) ~[na:1.8.0_121]
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85) ~[na:1.8.0_121]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_121]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_121]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_121]
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[na:1.8.0_121]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_121]
at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_121]
at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121) ~[httpclient-4.5.5.jar:4.5.5]
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180) ~[httpclient-4.5.5.jar:4.5.5]
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144) ~[httpclient-4.5.5.jar:4.5.5]
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134) ~[httpclient-4.5.5.jar:4.5.5]
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:610) ~[httpclient-4.5.5.jar:4.5.5]
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:445) ~[httpclient-4.5.5.jar:4.5.5]
at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835) ~[httpclient-4.5.5.jar:4.5.5]
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118) ~[httpclient-4.5.5.jar:4.5.5]
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.5.jar:4.5.5]
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173) ~[jersey-apache-client4-1.19.1.jar:1.19.1]
... 30 common frames omitted
2018-08-09 10:29:25.225 WARN 7964 --- [nfoReplicator-0] c.n.d.s.t.d.RetryableEurekaHttpClient : Request execution failed with message: java.net.ConnectException: Connection refused: connect
2018-08-09 10:29:25.225 WARN 7964 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient : DiscoveryClient_EUREKA-CLUSTER/xuchao:eureka-cluster:8761 - registration failed Cannot execute request on any known server
com.netflix.discovery.shared.transport.TransportException: Cannot execute request on any known server
at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:112) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:829) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) [eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.9.2.jar:1.9.2]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_121]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_121]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_121]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_121]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_121]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_121]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]
2018-08-09 10:29:25.225 WARN 7964 --- [nfoReplicator-0] c.n.discovery.InstanceInfoReplicator : There was a problem with the instance info replicator
com.netflix.discovery.shared.transport.TransportException: Cannot execute request on any known server
at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:112) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:829) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) ~[eureka-client-1.9.2.jar:1.9.2]
at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.9.2.jar:1.9.2]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_121]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_121]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_121]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_121]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_121]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_121]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]
分析日志可知，是在第一個節(jié)點eureka-server1啟動后，向eureka-server2注冊時連接拒絕(java.net.ConnectException: Connection refused: connect)導(dǎo)致，因為此時eureka-server2節(jié)點還未啟動，所有出現(xiàn)此類錯誤信息是正常的，eureka-server2啟動后，此類錯誤日志將不會出現(xiàn)。關(guān)于各類集群環(huán)境不同節(jié)點在順次啟動時都會出現(xiàn)類似錯誤信息的，大家不必驚慌！
在瀏覽器中分別訪問各自節(jié)點的地址、端口，http://eureka-server1:8761/、http://eureka-server2:8762/
從上面兩張圖可以看出，DS Replicas、registered-replicas、available-replicas分別有了對方的地址，即：相互Replicate、相互注冊，則說明Eureka集群成功。
2.2高可用性驗證
如果出現(xiàn)其中一個節(jié)點宕機，結(jié)果將會如何呢？
停掉eureka-server1服務(wù)作為模擬宕機，訪問http://eureka-server1:8761/顯示無法訪問，http://eureka-server2:8762/正常訪問，eureka-server2節(jié)點信息如下：
發(fā)生變化之處，如上圖標注，eureka-server1宕機后，eureka-server2依舊可以發(fā)現(xiàn)eureka-server1，而eureka-server1只是變?yōu)閡navailable-replicas而已，最終不會影響其他客戶端的注冊。當eureka-server1啟動后，一切自動恢復(fù)。
（其他高可用性的驗證，感興趣的可一一驗證）
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