前言
eureka 在springcloud体系中，主要实现一个注册中心的角色，所有的服务都将注册到eureke中，调用用者将从这里通过名称获取到对应的服务的IP集合列表。
作为一个分布式系统eureka在CAP中，选中了AP，优先保证可用性，放弃了强一致性，这样设计也符合注册中心的需要。
当发生网络分区故障（15分钟内超过85%的节点都没有正常的心跳），eureka会启用注册保护，即维持住当前心跳虽然失败的服务列表，并不进行删除。并能正常的提供查询服务（虽然不是最新）和注册服务（即不会同步到其他eureka节点），当网络恢复时，eureka会正确的同步信息，和恢复删除过期节点信息。
eureka的集群设计方式，采用了对等注册的形式完成。比如我们有三个节点的eureka集群，架构图如下
实现服务
简单的讲了下eureka的概念，下面我们进入编码模式。
当前最新的spring boot版本为2.1.7 我们将他作为我们的parent。主要是方便三方jar的版本管理和maven插件的使用。
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<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.7.RELEASE</version>
</parent>
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加入spring cloud的pom依赖，方便spring cloud 提供的相关jar的版本管理。这里需要将此依赖放入dependencyManagement中
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<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>
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有了这两个方便的pom之后。我们可以添加上eureka server的依赖。这里我将tomcat直接排除了，采用比较好用的undertow
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<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-undertow</artifactId>
</dependency>
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需要的依赖我们导入完毕，接下来我们需要配置插件，一个插件是spring-boot-maven-plugin，他会方便我们打出fatjar，还有一个插件是docker-maven-plugin方便直接构建出我们需要的镜像并推送到远程仓库。
你可以从我的这片博文如何构建SpringBoot的Docker镜像中了解更多.
那么加上插件之后完成的pom如下
pom.xml
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<?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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.7.RELEASE</version>
</parent>
<groupId>io.qingmu</groupId>
<artifactId>eureka</artifactId>
<version>0.0.1-SNAPSHOT</version>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Greenwich.SR2</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-undertow</artifactId>
</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>
<plugin>
<groupId>com.spotify</groupId>
<artifactId>docker-maven-plugin</artifactId>
<configuration>
<imageName>
freemanliu/eureka:v1.0.0
</imageName>
<registryUrl></registryUrl>
<workdir>/work</workdir>
<rm>true</rm>
<env>
<TZ>Asia/Shanghai</TZ>
<JAVA_OPTS>
-XX:+UnlockExperimentalVMOptions \
-XX:+UseCGroupMemoryLimitForHeap \
-XX:MaxRAMFraction=2 \
-XX:CICompilerCount=8 \
-XX:ActiveProcessorCount=8 \
-XX:+UseG1GC \
-XX:+AggressiveOpts \
-XX:+UseFastAccessorMethods \
-XX:+UseStringDeduplication \
-XX:+UseCompressedOops \
-XX:+OptimizeStringConcat
</JAVA_OPTS>
</env>
<baseImage>freemanliu/openjre:8.212</baseImage>
<cmd>
/sbin/tini java ${JAVA_OPTS} -jar ${project.build.finalName}.jar
</cmd>
<!--是否推送image-->
<pushImage>true</pushImage>
<resources>
<resource>
<directory>${project.build.directory}</directory>
<include>${project.build.finalName}.jar</include>
</resource>
</resources>
<serverId>docker-hub</serverId>
</configuration>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>build</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
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EurekaServiceApplication
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package io.qingmu;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
@SpringBootApplication
@EnableEurekaServer
public class EurekaServiceApplication {
public static void main(String[] args) {
SpringApplication.run(EurekaServiceApplication.class, args);
}
}
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application.yml
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server:
port: ${PORT:8761}
spring:
application:
name: eureka-service
management:
endpoints:
web:
exposure:
include: "*"
logging:
level:
com:
netflix:
eureka:
registry: error
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bootstrap.yml
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eureka:
server:
# 续期时间，即扫描失效服务的间隔时间（缺省为60*1000ms）
eviction-interval-timer-in-ms: 5000
client:
# eureka client间隔多久去拉取服务注册信息 默认30s
registry-fetch-interval-seconds: 30
fetch-registry: false
serviceUrl:
defaultZone: ${EUREKA_SERVER:http://127.0.0.1:${server.port}/eureka/}
instance:
# 心跳间隔时间，即发送一次心跳之后，多久在发起下一次（缺省为30s）
lease-renewal-interval-in-seconds: 10
# 在收到一次心跳之后，等待下一次心跳的空档时间，大于心跳间隔即可，即服务续约到期时间（缺省为90s）
lease-expiration-duration-in-seconds: 15
instance-id: ${EUREKA_INSTANCE_HOSTNAME:${spring.application.name}}:${server.port}@${random.long(1000000,9999999)}
hostname: ${EUREKA_INSTANCE_HOSTNAME:${spring.application.name}}
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完成的项目结构如下：
查看UI
运行application类，在浏览器中输入http://127.0.0.1:8761/ 你将看到单机版本的eureka的UI界面。
打包docker镜像，打开idea的终端，确保你配置好了docker插件中imageName和serverId之后。
如果顺利，你将会看到镜像被成功推送到远程仓库。这我推送的镜像是freemanliu/eureka:v1.0.0。
使用Docker部署eureka集群
这里使用三个机器分别是
eureka | host
- | -
eureka-0.eureka | 192.168.0.201 |
eureka-1.eureka | 192.168.0.202 |
eureka-2.eureka | 192.168.0.203 |
写入映射hosts
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cat > /etc/hosts << EOF
192.168.0.201 eureka-0.eureka
192.168.0.202 eureka-1.eureka
192.168.0.203 eureka-2.eureka
EOF
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201-eureka0
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docker run -it --rm --net host \
-e EUREKA_INSTANCE_HOSTNAME=eureka-0.eureka \
-e EUREKA_SERVER=http://eureka-0.eureka:8761/eureka/,http://eureka-1.eureka:8761/eureka/,http://eureka-2.eureka:8761/eureka/ \
freemanliu/eureka:v1.0.0
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202-eureka1
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docker run -it --rm --net host \
-e EUREKA_INSTANCE_HOSTNAME=eureka-1.eureka \
-e EUREKA_SERVER=http://eureka-0.eureka:8761/eureka/,http://eureka-1.eureka:8761/eureka/,http://eureka-2.eureka:8761/eureka/ \
freemanliu/eureka:v1.0.0
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203-eureka2
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docker run -it --rm --net host \
-e EUREKA_INSTANCE_HOSTNAME=eureka-2.eureka \
-e EUREKA_SERVER=http://eureka-0.eureka:8761/eureka/,http://eureka-1.eureka:8761/eureka/,http://eureka-2.eureka:8761/eureka/ \
freemanliu/eureka:v1.0.0
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打开浏览器访问 http://192.168.0.201:8761 可以发现我们的集群已经成功搭建好了。
在client使用
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eureka:
client:
serviceUrl:
defaultZone: http://192.168.0.201:8761/eureka/,http://192.168.0.202:8761/eureka/,http://192.168.0.203:8761/eureka/
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部署到kubernetes
这里采用statefulset部署，部署3个副本集的集群，如果你需要更多副本集，则需要改动EUREKA_INSTANCE_HOSTNAME中的URL
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# eureka-statefulset.yaml
---
apiVersion: v1
kind: Service
metadata:
name: eureka
labels:
app: eureka
spec:
ports:
- port: 8761
name: eureka
clusterIP: None
selector:
app: eureka
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: eureka
spec:
serviceName: "eureka"
replicas: 3
selector:
matchLabels:
app: eureka
template:
metadata:
labels:
app: eureka
spec:
containers:
- name: eureka
image: freemanliu/eureka:v1.0.0
ports:
- containerPort: 8761
resources:
limits:
# jvm会自动发现该限制
memory: 2Gi
env:
- name: MY_POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: JAVA_OPTS
value: -XX:+UnlockExperimentalVMOptions
-XX:+UseCGroupMemoryLimitForHeap
-XX:MaxRAMFraction=2
-XX:CICompilerCount=8
-XX:ActiveProcessorCount=8
-XX:+UseG1GC
-XX:+AggressiveOpts
-XX:+UseFastAccessorMethods
-XX:+UseStringDeduplication
-XX:+UseCompressedOops
-XX:+OptimizeStringConcat
- name: EUREKA_SERVER
value: "http://eureka-0.eureka:8761/eureka/,http://eureka-1.eureka:8761/eureka/,http://eureka-2.eureka:8761/eureka/"
- name: EUREKA_INSTANCE_HOSTNAME
value: ${MY_POD_NAME}.eureka
podManagementPolicy: "Parallel"
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部署
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kubectl apply -f eureka-statefulset.yaml
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查看部署状态
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freemandeMacBook-Pro:qingmu freeman$ kubectl get pods -owide | grep eureka
eureka-0 1/1 Running 0 126m 172.224.5.40 node3 <none> <none>
eureka-1 1/1 Running 0 126m 172.224.3.131 node1 <none> <none>
eureka-2 1/1 Running 0 126m 172.224.7.243 node6 <none> <none>
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通过浏览器访问http://podip:8761
在client使用，当都处于default namespace时
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eureka:
client:
serviceUrl:
defaultZone: http://eureka-0.eureka:8761/eureka/,http://eureka-1.eureka:8761/eureka/,http://eureka-2.eureka:8761/eureka/
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都处于非default namespace 卡的惨不忍睹啊 是输入法的问题妈
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eureka:
client:
serviceUrl:
defaultZone: http://eureka-0.eureka.default:8761/eureka/,http://eureka-1.eureka.default:8761/eureka/,http://eureka-2.eureka.default:8761/eureka/
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Github 地址
完整的代码我上传到了github 你可以从这个https://github.com/qingmuio/eureka 获取到代码。