本文介绍了一些关于SpringCloud Eureka的基本概念与应用。

Eureka角色

服务端：EurekaServer，服务端，注册中心。负责心跳监控，记录服务信息

客户端：EurekaClient，分为消费者和提供者。

Eureka的作用

eureka服务类似注册中心：

服务消费者和提供者将服务信息注册到注册中心
消费者向注册中心拉取提供者的新消息
通过负载均衡进行选择
实现远程调用

注册中心使用心跳续约，随时监控服务状态

Eureka搭建

搭建服务步骤如下：

创建模块，引入spring-cloud-starter-netflix-eureka-server依赖

<!-- Eureka服务端 -->
<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
  <version>2.2.1.RELEASE</version>
</dependency>

如果父工程中已经选好了springcloud的版本以及相关依赖，这里不需要填写版本号

编写启动类，并添加@EnableEurekaServer注解
编写yml配置文件，服务端口、服务名称、地址信息（用于eureka集群通信）

# Tomcat
server:
  port: 9099

# Spring
spring:
  application:
    # 应用名称
    name: hms_eureka
eureka:
  client:
    sevice-url:
      defaultZone: http://localhost:${server.port}/eureka
    # 这里选择不将自己注册 
    register-with-eureka: false
    fetch-registry: false

服务注册

在依赖中引入

<!-- Eureka客户端 -->
<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

同时在application.yml中配置eureka相关信息

eureka:
  client:
    service-url:
      defaultZone: http://localhost:9099/eureka

注：启动类上要加上@EnableEurekaServer注解

一直遇到一个问题，日志内容如下：

2023-08-30 16:57:34.306  INFO 1076 --- [           main] com.magus.UserServiceApplication         : No active profile set, falling back to default profiles: default
2023-08-30 16:57:34.580  INFO 1076 --- [           main] o.s.cloud.context.scope.GenericScope     : BeanFactory id=24ae86d6-4a71-3421-838c-868a60323ef7
2023-08-30 16:57:34.621  INFO 1076 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration' of type [org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration$$EnhancerBySpringCGLIB$$9adaa148] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2023-08-30 16:57:34.632  INFO 1076 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration' of type [org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration$$EnhancerBySpringCGLIB$$b6f4a445] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2023-08-30 16:57:34.644  WARN 1076 --- [           main] c.n.c.sources.URLConfigurationSource     : No URLs will be polled as dynamic configuration sources.
2023-08-30 16:57:34.644  INFO 1076 --- [           main] c.n.c.sources.URLConfigurationSource     : To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
2023-08-30 16:57:34.649  WARN 1076 --- [           main] c.n.c.sources.URLConfigurationSource     : No URLs will be polled as dynamic configuration sources.
2023-08-30 16:57:34.649  INFO 1076 --- [           main] c.n.c.sources.URLConfigurationSource     : To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
2023-08-30 16:57:36.516  INFO 1076 --- [           main] o.s.cloud.commons.util.InetUtils         : Cannot determine local hostname
2023-08-30 16:57:38.145  INFO 1076 --- [           main] o.s.cloud.commons.util.InetUtils         : Cannot determine local hostname
2023-08-30 16:57:38.203  INFO 1076 --- [           main] o.s.c.n.eureka.InstanceInfoFactory       : Setting initial instance status as: STARTING
2023-08-30 16:57:38.224  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Initializing Eureka in region us-east-1
2023-08-30 16:57:38.855  INFO 1076 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using JSON encoding codec LegacyJacksonJson
2023-08-30 16:57:38.855  INFO 1076 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using JSON decoding codec LegacyJacksonJson
2023-08-30 16:57:38.928  INFO 1076 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using XML encoding codec XStreamXml
2023-08-30 16:57:38.929  INFO 1076 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using XML decoding codec XStreamXml
2023-08-30 16:57:39.042  INFO 1076 --- [           main] c.n.d.s.r.aws.ConfigClusterResolver      : Resolving eureka endpoints via configuration
2023-08-30 16:57:39.460  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Disable delta property : false
2023-08-30 16:57:39.461  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Single vip registry refresh property : null
2023-08-30 16:57:39.461  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Force full registry fetch : false
2023-08-30 16:57:39.461  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Application is null : false
2023-08-30 16:57:39.461  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Registered Applications size is zero : true
2023-08-30 16:57:39.461  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Application version is -1: true
2023-08-30 16:57:39.461  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Getting all instance registry info from the eureka server
2023-08-30 16:57:39.535  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : The response status is 200
2023-08-30 16:57:39.536  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Starting heartbeat executor: renew interval is: 30
2023-08-30 16:57:39.538  INFO 1076 --- [           main] c.n.discovery.InstanceInfoReplicator     : InstanceInfoReplicator onDemand update allowed rate per min is 4
2023-08-30 16:57:39.541  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Discovery Client initialized at timestamp 1693385859540 with initial instances count: 0
2023-08-30 16:57:39.542  INFO 1076 --- [           main] o.s.c.n.e.s.EurekaServiceRegistry        : Registering application USER-SERVICE with eureka with status UP
2023-08-30 16:57:39.543  INFO 1076 --- [           main] com.netflix.discovery.DiscoveryClient    : Saw local status change event StatusChangeEvent [timestamp=1693385859543, current=UP, previous=STARTING]
2023-08-30 16:57:39.544  INFO 1076 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_USER-SERVICE/localhost:user-service:9999: registering service...
2023-08-30 16:57:39.554  INFO 1076 --- [           main] com.magus.UserServiceApplication         : Started UserServiceApplication in 9.058 seconds (JVM running for 10.165)
2023-08-30 16:57:39.556  INFO 1076 --- [       Thread-5] o.s.c.n.e.s.EurekaServiceRegistry        : Unregistering application USER-SERVICE with eureka with status DOWN
2023-08-30 16:57:39.557  WARN 1076 --- [       Thread-5] com.netflix.discovery.DiscoveryClient    : Saw local status change event StatusChangeEvent [timestamp=1693385859557, current=DOWN, previous=UP]
2023-08-30 16:57:39.561  INFO 1076 --- [       Thread-5] com.netflix.discovery.DiscoveryClient    : Shutting down DiscoveryClient ...
2023-08-30 16:57:39.602  INFO 1076 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_USER-SERVICE/localhost:user-service:9999 - registration status: 204
2023-08-30 16:57:39.603  INFO 1076 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_USER-SERVICE/localhost:user-service:9999: registering service...
2023-08-30 16:57:39.614  INFO 1076 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_USER-SERVICE/localhost:user-service:9999 - registration status: 204
2023-08-30 16:57:39.615  INFO 1076 --- [       Thread-5] com.netflix.discovery.DiscoveryClient    : Unregistering ...
2023-08-30 16:57:39.630  INFO 1076 --- [       Thread-5] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_USER-SERVICE/localhost:user-service:9999 - deregister  status: 200
2023-08-30 16:57:39.637  INFO 1076 --- [       Thread-5] com.netflix.discovery.DiscoveryClient    : Completed shut down of DiscoveryClient