SpringCloud服务注册中心双节点集群(Eureka集群)

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06/23 23:33
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0、前言

        最近在进行重构一个新项目,为了后续更好的落地,适应于日新月异的技术更新,进行了各方的技术选型及技术预研,最终选型基于微服务架构体系进行开发重构。项目构建前最重要的一步就是要想清楚,整体的部署架构、高可用性(HA)等等,做好前期的部署架构技术调研,确定最终方案。

        在微服务架构体系中,核心技术便是Spring Cloud,通过登录官网查看SpringCloud已经集成了好多优质的项目,供我们使用借鉴。而SpringCloud Eureka是云端服务发现,一个基于 REST 的服务,用于定位服务,以实现云端中间层服务发现和故障转移,并且支持集群部署。因此,本次部署架构技术方案选型打算采用Eureka集群。

(关于Eureka服务注册与发现请查看上一章节内容【SpringCloud系列】一、SpringCloud服务注册与发现(Eureka))

         本文将阐述SpringCloud服务注册中心双节点集群(Eureka集群)方案及集群demo。


1、Eureka集群概述

1.1 基本原理

 

如上图,是Eureka集群配置图。

- 不同节点的Eureka Server通过Replicate(复制)进行数据同步
- Application Service为服务提供者
- Application Client为服务消费者
- Make Remote Call完成一次服务调用

        服务启动后向Eureka注册,Eureka Server会将注册信息向其他Eureka Server进行同步,当服务消费者要调用服务提供者,则向服务注册中心获取服务提供者地址(即:服务应用名,spring.application.name参数配置),然后会将服务提供者地址缓存在本地,下次再调用时,则直接从本地缓存中取,完成一次调用。

        当服务注册中心Eureka Server检测到服务提供者因为宕机、网络原因不可用时,则在服务注册中心将服务置为DOWN状态,并把当前服务提供者状态向订阅者发布,订阅过的服务消费者更新本地缓存。

        服务提供者在启动后,周期性(默认30秒)向Eureka Server发送心跳,以证明当前服务是可用状态。Eureka Server在一定的时间(默认90秒)未收到客户端的心跳,则认为服务宕机,注销该实例。

1.2 Eureka自我保护机制

        在默认配置中,Eureka Server在默认90s没有得到客户端的心跳,则注销该实例,但是往往因为微服务跨进程调用,网络通信往往会面临着各种问题,比如微服务状态正常,但是因为网络分区故障时,Eureka Server注销服务实例则会让大部分微服务不可用,这很危险,因为服务明明没有问题。

         为了解决这个问题,Eureka 有自我保护机制,通过在Eureka Server配置如下参数,可启动保护机制。

eureka.server.enable-self-preservation=true

         它的原理是,当Eureka Server节点在短时间内丢失过多的客户端时(可能发送了网络故障),那么这个节点将进入自我保护模式,不再注销任何微服务,当网络故障回复后,该节点会自动退出自我保护模式。

1.3 Eureka高可用集群

        理论上来讲,因为服务消费者本地缓存了服务提供者的地址,即使Eureka Server宕机,也不会影响服务之间的调用,但是一旦新服务上线,已经在缓存在本地的服务提供者不可用了,服务消费者也无法知道,所以保证Eureka Server的高可用还是很有必要的。

        在分布式系统中,任何的地方存在单点,整个体系就不是高可用的,Eureka 也一样,在上面的架构图中Eureka Server不是以单点存在的,而是以集群的方式对外提供服务。


2、Eureka双中心节点集群

本节以具体示例说明Eureka集群及配置。

2.1 创建Eureka Server

(1)新建springCloudEurekaCluster项目作为Eureka Server集群项目:

 

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集群时,需要部署多个节点,则需要同一个项目,使用不同的配置。因此,在本例中使用springCloudEurekaCluster一个项目通过不同的启动参数来启动占用不同端口的两个Server服务,来模拟Eureka集群。则使用下面三个*.properties配置文件:

  • application.properties
  • application-eureka-server1.properties
  • application-eureka-server2.properties

application.properties

#应用名
spring.application.name=eureka-cluster

application-eureka-server1.properties

##eureka-server1节点配置,配置参数--spring.profiles.active=eureka-server1来启动该环境
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节点配置,配置参数--spring.profiles.active=eureka-server2来启动该环境
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配置文件设置了不同的端口(server.port),重点是参数eureka.client.serviceUrl.defaultZone,分别配置对方的地址作为Eureka Client进行相互注册。由于采用了参数配置eureka.instance.hostname及http://eureka-server1的写法,则需要在进行hosts的配置,window在C:\Windows\System32\drivers\etc\hosts,Linux是在/etc/host,此处,以我windows本机说明,在hosts文件中最近如下配置:

127.0.0.1 eureka-server1
127.0.0.1 eureka-server2

(3)新建启动类。

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集群启动类
 * @author xcbeyond
 * 2018年8月7日上午10:34:01
 */
@SpringBootApplication
//开启对EurekaServer的支持,即:作为Eureka服务端
@EnableEurekaServer
//开启作为Eureka Server的客户端的支持
@EnableDiscoveryClient
public class EurekaClusterApplication {
	public static void main(String[] args) {
		SpringApplication.run(EurekaClusterApplication.class, args);
	}
}

重点添加@EnableEurekaServer注解,开启对EurekaServer的支持,即:作为Eureka服务端。

项目源码:https://download.csdn.net/download/xcbeyond/10592831

2.2.Eureka集群启动及验证

2.2.1 集群启动

      在创建Eureka server项目时,创建了两个properties配置文件,作为集群不同的节点配置文件,在启动项目时,只需指定启动参数--spring.profiles.active=eureka-server1来指定对应配置环境,运行启动类即可。Eclipse IDE开发环境下,配置启动参数方式如下:

 

在启动第一个节点eureka-server1过程中,会持续出现如下错误信息:

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,是在第一个节点eureka-server1启动后,向eureka-server2注册时连接拒绝(java.net.ConnectException: Connection refused: connect)导致,因为此时eureka-server2节点还未启动,所有出现此类错误信息是正常的,eureka-server2启动后,此类错误日志将不会出现。关于各类集群环境不同节点在顺次启动时都会出现类似错误信息的,大家不必惊慌!

        在浏览器中分别访问各自节点的地址、端口,http://eureka-server1:8761/http://eureka-server2:8762/

 

从上面两张图可以看出,DS Replicas、registered-replicas、available-replicas分别有了对方的地址,即:相互Replicate、相互注册,则说明Eureka集群成功。

2.2高可用性验证

如果出现其中一个节点宕机,结果将会如何呢?

停掉eureka-server1服务作为模拟宕机,访问http://eureka-server1:8761/显示无法访问,http://eureka-server2:8762/正常访问,eureka-server2节点信息如下:

 

发生变化之处,如上图标注,eureka-server1宕机后,eureka-server2依旧可以发现eureka-server1,而eureka-server1只是变为unavailable-replicas而已,最终不会影响其他客户端的注册。当eureka-server1启动后,一切自动恢复。

(其他高可用性的验证,感兴趣的可一一验证)

 

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重构?应用注册中心?不是在讲段子吧?
06/28 11:51
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xcbeyond博主
你理解错了,我是说重构自己的项目,而不是注册中心,哈哈
06/30 09:52
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图片挂了
06/24 10:50
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