微服务架构➖SpringCloud➖Eureka

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1.Spring Cloud Eureka简介

注册发现中心

Eureka 来源于古希腊词汇，意为“发现了”。在软件领域， Eureka 是 Netflix 在线影片公司开源的一个服务注册与发现的组件，和其他 Netflix 公司的服务组件（例如负载均衡、熔断器、网关等）一起，被 Spring Cloud 社区整合为 Spring Cloud Netflix 模块。

Eureka 是 Netflix 贡献给 Spring Cloud 的一个框架！Netflix 给 Spring Cloud 贡献了很多框架，后面我们会学习到！

2.Spring Cloud Eureka 和 Zookeeper 的区别

2.1 什么是CAP 原则（面试）

在分布式微服务里面 CAP 定理

问：为什么 zookeeper 不适合做注册中心？

CAP 原则又称 CAP 定理，指的是在一个分布式系统中，

一致性（Consistency）

可用性（Availability）

分区容错性（Partition tolerance）（这个特性是不可避免的）

CAP 原则指的是，这三个要素最多只能同时实现两点，不可能三者兼顾。

问题：

2022-09-27 10:15:49.176  INFO 23496 --- [           main] c.n.d.s.t.d.RedirectingEurekaHttpClient  : Request execution error. endpoint=DefaultEndpoint{ serviceUrl='http://localhost:8761/eureka/}, exception=java.net.ConnectException: Connection refused: connect stacktrace=com.sun.jersey.api.client.ClientHandlerException: java.net.ConnectException: Connection refused: connect
	at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187)
	at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123)
	at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27)
	at com.sun.jersey.api.client.Client.handle(Client.java:652)
	at com.sun.jersey.api.client.WebResource.handle(WebResource.java:682)
	at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74)
	at com.sun.jersey.api.client.WebResource$Builder.get(WebResource.java:509)
	at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.getApplicationsInternal(AbstractJerseyEurekaHttpClient.java:196)
	at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.getApplications(AbstractJerseyEurekaHttpClient.java:167)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137)
	at com.netflix.discovery.shared.transport.decorator.MetricsCollectingEurekaHttpClient.execute(MetricsCollectingEurekaHttpClient.java:73)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137)
	at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.executeOnNewServer(RedirectingEurekaHttpClient.java:121)
	at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.execute(RedirectingEurekaHttpClient.java:80)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137)
	at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:120)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137)
	at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134)
	at com.netflix.discovery.DiscoveryClient.getAndStoreFullRegistry(DiscoveryClient.java:1101)
	at com.netflix.discovery.DiscoveryClient.fetchRegistry(DiscoveryClient.java:1014)
	at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:441)
	at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:283)
	at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:279)
	at org.springframework.cloud.netflix.eureka.CloudEurekaClient.<init>(CloudEurekaClient.java:67)
	at org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration$RefreshableEurekaClientConfiguration.eurekaClient(EurekaClientAutoConfiguration.java:316)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:652)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:637)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1341)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1181)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$1(AbstractBeanFactory.java:363)
	at org.springframework.cloud.context.scope.GenericScope$BeanLifecycleWrapper.getBean(GenericScope.java:389)
	at org.springframework.cloud.context.scope.GenericScope.get(GenericScope.java:186)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:360)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
	at org.springframework.aop.target.SimpleBeanTargetSource.getTarget(SimpleBeanTargetSource.java:35)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:192)
	at com.sun.proxy.$Proxy97.getApplications(Unknown Source)
	at org.springframework.cloud.netflix.eureka.server.EurekaServerAutoConfiguration.peerAwareInstanceRegistry(EurekaServerAutoConfiguration.java:154)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:652)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:637)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1341)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1181)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
	at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1307)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
	at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:886)
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:790)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:540)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1341)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1181)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
	at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1307)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:657)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640)
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1425)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:897)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:755)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747)
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:402)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:312)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1247)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1236)
	at com.zmz.EurekaServerApplication.main(EurekaServerApplication.java:12)
Caused by: java.net.ConnectException: Connection refused: connect
	at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
	at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
	at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
	at java.net.Socket.connect(Socket.java:606)
	at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121)
	at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180)
	at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144)
	at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134)
	at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:605)
	at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:440)
	at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835)
	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118)
	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)
	at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173)
	... 102 more

2022-09-27 10:15:49.176  WARN 23496 --- [           main] c.n.d.s.t.d.RetryableEurekaHttpClient    : Request execution failed with message: java.net.ConnectException: Connection refused: connect
2022-09-27 10:15:49.176  INFO 23496 --- [           main] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_EUREKA-SERVER/localhost:eureka-server:8761 - was unable to refresh its cache! This periodic background refresh will be retried in 30 seconds. status = Cannot execute request on any known server stacktrace = 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)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137)
	at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77)
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134)
	at com.netflix.discovery.DiscoveryClient.getAndStoreFullRegistry(DiscoveryClient.java:1101)
	at com.netflix.discovery.DiscoveryClient.fetchRegistry(DiscoveryClient.java:1014)
	at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:441)
	at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:283)
	at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:279)
	at org.springframework.cloud.netflix.eureka.CloudEurekaClient.<init>(CloudEurekaClient.java:67)
	at org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration$RefreshableEurekaClientConfiguration.eurekaClient(EurekaClientAutoConfiguration.java:316)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:652)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:637)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1341)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1181)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$1(AbstractBeanFactory.java:363)
	at org.springframework.cloud.context.scope.GenericScope$BeanLifecycleWrapper.getBean(GenericScope.java:389)
	at org.springframework.cloud.context.scope.GenericScope.get(GenericScope.java:186)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:360)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
	at org.springframework.aop.target.SimpleBeanTargetSource.getTarget(SimpleBeanTargetSource.java:35)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:192)
	at com.sun.proxy.$Proxy97.getApplications(Unknown Source)
	at org.springframework.cloud.netflix.eureka.server.EurekaServerAutoConfiguration.peerAwareInstanceRegistry(EurekaServerAutoConfiguration.java:154)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:652)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:637)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1341)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1181)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
	at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1307)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
	at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:886)
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:790)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:540)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1341)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1181)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
	at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1307)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:657)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640)
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119)
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1425)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:897)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:755)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747)
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:402)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:312)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1247)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1236)
	at com.zmz.EurekaServerApplication.main(EurekaServerApplication.java:12)

报错原因：在默认设置下，eureka服务注册中心会去注册中心获取其他服务的地址，也会将自己作为客户端来尝试注册它自己.

解决办法：

禁用它的客户端注册行为:

在 eureka 的 application.yml中增加
eureka:
  client:
    fetch-registry: false    #要不要去注册中心获取其他服务的地址 , 解决eureka启动时报错
    register-with-eureka: false    #是否当前客户端要注册到eureka

4.搭建 Eureka-server

4.1 创建项目,选择依赖

4.2 分析 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <!-- 实质还是 springboot 项目-->
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.12.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.zmz</groupId>
    <artifactId>eureka-server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>eureka-server</name>
    <description>eureka-server Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <!--	这里控制了 springcloud 的版本-->
        <spring-cloud.version>Hoxton.SR12</spring-cloud.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

<!--      eureka服务端  -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <!-- 依赖管理，cloud 的依赖-->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

4.3 启动类

package com.zmz;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer	//启动eureka服务标识
public class EurekaServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(EurekaServerApplication.class, args);
    }

}

4.4 修改配置文件

server:
  port: 8761
spring:
  application:
    name: eureka-server

eureka:
  client:
    fetch-registry: false    #要不要去注册中心获取其他服务的地址 , 解决eureka启动时报错
    register-with-eureka: true    #是否当前客户端要注册到eureka

4.5 访问测试

Eureka-Server 不仅提供让别人注册的功能，它也能注册到别人里面，自己注册自己

所以，在启动项目时，默认会注册自己，我们也可以关掉这个功能。

http://localhost:8761/

5.搭建 Eureka-client

5.1 创建项目,选择依赖

5.2 分析 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.12.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.zmz</groupId>
    <artifactId>eureka-client-a</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>eureka-client-a</name>
    <description>eureka-client-a Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR12</spring-cloud.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

5.3 启动类

package com.zmz;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient
public class EurekaClientAApplication {

    public static void main(String[] args) {
        SpringApplication.run(EurekaClientAApplication.class, args);
    }

}

5.4 修改配置文件

server:
  port: 8001
spring:
  application:
    name: eureka-client-a
eureka:
  client:
    service-url:	#eureka 服务端和客户端的交互地址
     defaultZone: http://127.0.0.1:8761/eureka

5.5 访问测试

6.搭建多个实例的Eureka-client

6.1 IDEA 启动多台服务操

7.构建高可用的 Eureka-Server 集群

7.1 修改配置文件

service-1

#单机
#server:
#  port: 8761
#spring:
#  application:
#    name: eureka-server
#
#
#eureka:   #eureka 分为三类，server client 实例   eureka即使服务端又是客户端
#  server:
#    eviction-interval-timer-in-ms: 10000 #逐出间隔计时器毫秒  服务端间隔多少s做定期删除
#    renewal-percent-threshold: 0.85 #续订百分比阈值  超过85%的应用没有进行续约，那么eureka会保护服务  不会剔除
#  instance:
#    hostname: localhost
#    instance-id: ${eureka.instance.hostname}:${spring.application.name}:${server.port} #主机名:应用名:端口号
#    prefer-ip-address: true  #以ip的形式显示具体服务信息
#    lease-renewal-interval-in-seconds: 5 #租约续订间隔秒


#集群
server:
    port: 8761  # eureka的默认端口  6379  8080  3306   8848
spring:
    application:
        name: eureka-server  # 应用名称 不要使用特殊字符
eureka:
    client:
      service-url: # 你不写 默认 8761
            defaultZone: http://localhost:8762/eureka,http://localhost:8763/eureka
#      fetch-registry: false #是否将自己进行注册成客户端
    instance: # 实例的配置
        instance-id: ${eureka.instance.hostname}:${spring.application.name}:${server.port}   # 主机名称 : 应用名称 : 端口号
        hostname: localhost  # 主机名称 或者服务的ip
        prefer-ip-address: true # 以ip的形式显示具体的服务信息
#        lease-renewal-interval-in-seconds: 5  # 服务实例的续约的时间间隔

service-2

server:
  port: 8762
spring:
  application:
    name: eureka-server # 应用名称不能改
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka,http://localhost:8763/eureka
#    fetch-registry: false
  instance: # 实例的配置
    instance-id: ${eureka.instance.hostname}:${spring.application.name}:${server.port}   # 主机名称 : 应用名称 : 端口号
    hostname: localhost  # 主机名称 或者服务的ip
    prefer-ip-address: true # 以ip的形式显示具体的服务信息
    lease-renewal-interval-in-seconds: 5  # 服务实例的续约的时间间隔

service-3

server:
  port: 8763
spring:
  application:
    name: eureka-server # 应用名称不能改
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka,http://localhost:8762/eureka
  #    fetch-registry: false
  instance: # 实例的配置
    instance-id: ${eureka.instance.hostname}:${spring.application.name}:${server.port}   # 主机名称 : 应用名称 : 端口号
    hostname: localhost  # 主机名称 或者服务的ip
    prefer-ip-address: true # 以ip的形式显示具体的服务信息
    lease-renewal-interval-in-seconds: 5  # 服务实例的续约的时间间隔

7.2 测试访问

image-20220928111924183转存失败，建议直接上传图片文件

发现并没有出现集群信息，只是同一个服务 server 启动了多台没有数据交互不是真正意义上的集群

原因是因为：

http://localhost:8761/eureka/,http://localhost:8762/eureka/ 这样写，eureka 认为只有一个机器，就是 localhost 所以这里面不能写成一样修改 hosts 文件： C:\Windows\System32\drivers\etc 如果你修改了 hosts 文件发现没有生效，记得在 cmd 里面刷新一下 ipconfig /flushdn。

7.3 重新修改配置文件

7.4 测试查看集群信息

7.5 最终优化配置文件

service-1

#集群的终极方案
server:
    port: 8761  # eureka的默认端口  6379  8080  3306   8848
spring:
    application:
        name: eureka-server  # 应用名称 不要使用特殊字符
eureka:
    client:
        service-url: # 你不写 默认 8761
            defaultZone: http://clearlove1:8761/eureka,http://clearlove2:8762/eureka,http://clearlove3:8763/eureka
    instance: # 实例的配置
        instance-id: ${spring.application.name}:${server.port}   # 主机名称 : 应用名称 : 端口号
#        hostname: peer1  # 主机名称 或者服务的ip
        prefer-ip-address: true # 以ip的形式显示具体的服务信息
        lease-renewal-interval-in-seconds: 5  # 服务实例的续约的时间间隔

service-2

#集群的终极方案
server:
  port: 8762
spring:
  application:
    name: eureka-server # 应用名称不能改
eureka:
  client:
    service-url:
      defaultZone: http://clearlove1:8761/eureka,http://clearlove3:8763/eureka
  instance: # 实例的配置
    instance-id: ${eureka.instance.hostname}:${spring.application.name}:${server.port}   # 主机名称 : 应用名称 : 端口号
    hostname: clearlove2  # 主机名称 或者服务的ip
    prefer-ip-address: true # 以ip的形式显示具体的服务信息
    lease-renewal-interval-in-seconds: 5  # 服务实例的续约的时间间隔

service-3

#集群的终极方案
server:
  port: 8763
spring:
  application:
    name: eureka-server # 应用名称不能改
eureka:
  client:
    service-url:
      defaultZone: http://clearlove1:8761/eureka,http://clearlove2:8763/eureka
  instance: # 实例的配置
    instance-id: ${eureka.instance.hostname}:${spring.application.name}:${server.port}   # 主机名称 : 应用名称 : 端口号
    hostname: clearlove3  # 主机名称 或者服务的ip
    prefer-ip-address: true # 以ip的形式显示具体的服务信息
    lease-renewal-interval-in-seconds: 5  # 服务实例的续约的时间间隔

7.6 集群的使用

7.6.1 改造 eureka-client-a 的配置文件

server:
  port: 8001
spring:
  application:
    name: eureka-client-a
eureka:
  client:
    service-url:  #eureka 服务端和客户端的交互地址
      defaultZone: http://clearlove1:8761/eureka,http://clearlove2:8762/eureka,http://clearlove3:8763/eureka
    register-with-eureka: true #注册自己到eureka上
    fetch-registry: true #拉取服务列表
  instance:
    instance-id: ${spring.application.name}:${server.port} #注册eureka-server的实例名称
    lease-renewal-interval-in-seconds: 30  #eureka客户端向服务端发送心跳时间，每隔30s发送一次

7.6.2 测试

7.6.3 宕机一台 server

Eureka server 的集群里面，没有主机和从机的概念，节点都是对等的，只有集群里面有一个集群存活，就能保证服务的可用性。（主机（写）从（读））只要有一台存活，服务就能注册和调用。

7.6.4 分布式数据一致性协议—Paxos、raft

thesecretlivesofdata.com/raft/

zk 是 Paxos eureka 没有分布式数据一致性的机制节点都是相同的 nacos raft 在有主从模式的集群中一般都要遵循这样的协议才可以稳定对外提供服务 Zookeeper Paxos Nacos raft

8.RestTemplate

8.1 创建项目03-rest-tamplate

编写Controller接口，实体类User

package com.zmz.controller;

import com.zmz.pojo.User;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

/**
 * @ProjectName: springcloud
 * @Package: com.zmz.controller
 * @ClassName: TestController
 * @Author: 张晟睿
 * @Date: 2022/9/29 19:45
 * @Version: 1.0
 */
@RestController
public class TestController {

    @GetMapping("testGet")
    public String get(String name) {
        System.out.println(name);
        return "OK";
    }

    @PostMapping("testPost1")
    public String testPost1(@RequestBody User user) {
        System.out.println(user);
        return "OK";
    }

    @PostMapping("testPost2")
    public String testPost2(User user) {
        System.out.println(user);
        return "OK";
    }
}

User.java

package com.zmz.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @ProjectName: springcloud
 * @Package: com.zmz.pojo
 * @ClassName: User
 * @Author: 张晟睿
 * @Date: 2022/9/29 19:46
 * @Version: 1.0
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private String name;
    private Integer age;
}

8.2 测试类

package com.zmz;

import com.sun.org.apache.bcel.internal.generic.NEW;
import com.zmz.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;

import java.util.HashMap;

@SpringBootTest
class RestTemplateApplicationTests {

    @Test
    void testGet() {
        RestTemplate restTemplate = new RestTemplate();
        String url = "http://localhost:8080/testGet?name=zmz";
//        String result= restTemplate.getForObject(url, String.class);
        ResponseEntity<String> entity = restTemplate.getForEntity(url, String.class);
        System.out.println(entity);
    }

    @Test
    void testPost1() {
        RestTemplate restTemplate = new RestTemplate();

        String url = "http://localhost:8080/testPost1";
        User user = new User("zmz", 20);
        String result = restTemplate.postForObject(url, user, String.class);
        System.out.println(result);
    }

    @Test
    void testPost2() {
        RestTemplate restTemplate = new RestTemplate();

        String url = "http://localhost:8080/testPost2";

        /**
         * 文档连接
         * https://blog.csdn.net/weixin_42831477/article/details/106916928?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522166445420316782388011115%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=166445420316782388011115&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~sobaiduend~default-1-106916928-null-null.142^v51^pc_rank_34_1,201^v3^control_2&utm_term=LinkedMultiValueMap&spm=1018.2226.3001.4187
         * 使用map进行表单模拟值时，后端User实体类接收到的值为空User(name=null, age=null)
         * 这里需要使用LinkedMultiValueMap来模拟表单进行实现。
         *
         */
        HashMap<String, Object> map = new HashMap<>();
        map.put("name","zmz");
        map.put("age",19);
        String result = restTemplate.postForObject(url, map, String.class);
        System.out.println(result);
    }

}

SpringCloud微服务进阶学习➖Eureka

微服务架构➖SpringCloud➖Eureka

关于作者

1.Spring Cloud Eureka简介

2.Spring Cloud Eureka 和 Zookeeper 的区别

2.1 什么是CAP 原则（面试）

4.搭建 Eureka-server

4.1 创建项目,选择依赖

4.2 分析 pom.xml

4.3 启动类

4.4 修改配置文件

4.5 访问测试

5.搭建 Eureka-client

5.1 创建项目,选择依赖

5.2 分析 pom.xml

5.3 启动类

5.4 修改配置文件

5.5 访问测试

6.搭建 多个实例的Eureka-client

6.1 IDEA 启动多台服务操

7.构建高可用的 Eureka-Server 集群

7.1 修改配置文件

service-1

service-2

service-3

7.2 测试访问

7.3 重新修改配置文件

7.4 测试查看集群信息

7.5 最终优化配置文件

service-1

service-2

service-3

7.6 集群的使用

7.6.1 改造 eureka-client-a 的配置文件

7.6.2 测试

7.6.3 宕机一台 server

7.6.4 分布式数据一致性协议—Paxos、raft

8.RestTemplate

8.1 创建项目03-rest-tamplate

8.2 测试类

6.搭建多个实例的Eureka-client