全文速览：

• 获取源码并加载环境
• spring-cloud-kubernetes下的示例
• mac minikube 本地构建执行SpringCloud-Kubernetes-Example

文章背景：

2019年开始 SpringCloud 开始向 K8S容器化流程演变，逐步诞生了【Spring-Cloud-Kubernetes】

环境要求：

• maven 3.+
• jdk17

获取源码并加载环境

从github仓库获取源码

git clone https://github.com/spring-cloud/spring-cloud-kubernetes.git 

导入IDEA后，确认以下构建环境

• maven 3.+
• jdk17
• 当前springcloudkubernetes版本：3.1.0-SNAPSHOT
• spring-cloud-build 4.1.0-SNAPSHOT

由于代码涉及snapshot库的代码拉取（体现Spring全家桶的协同），需要关注项目根目录下的.setting文件，作为一般本地maven文件的补充，主要关注仓库部分，构建的时候可以直接选定这个setting文件，消除全项目红波浪线的问题。

确认以上环境后

./mvnw clean package -Dmaven.test.skip=true

保持网络通畅，期间会需要连接docker，现在打包工具，确定JRE版本，下载JRE版本，打包到镜像仓库等动作。

spring-cloud-kubernetes下的示例

使用spring-cloud-kubernetes下的example体验springcloud与kubernetes的融合与互动

/spring-cloud-kubernetes/spring-cloud-kubernetes-examples/kubernetes-leader-election-examplemvn spring-boot:build-image -Dspring-boot.build-image.imageName=org/kubernetes-leader-election-example:~$ docker images
REPOSITORY                                                                    TAG       IMAGE ID       CREATED         SIZE
busybox                                                                       latest    a416a98b71e2   4 weeks ago     4.26MB
registry.cn-hangzhou.aliyuncs.com/google_containers/kube-apiserver            v1.24.1   e9f4b425f919   15 months ago   130MB
registry.cn-hangzhou.aliyuncs.com/google_containers/kube-scheduler            v1.24.1   18688a72645c   15 months ago   51MB
registry.cn-hangzhou.aliyuncs.com/google_containers/kube-proxy                v1.24.1   beb86f5d8e6c   15 months ago   110MB
registry.cn-hangzhou.aliyuncs.com/google_containers/kube-controller-manager   v1.24.1   b4ea7e648530   15 months ago   119MB
registry.cn-hangzhou.aliyuncs.com/google_containers/etcd                      3.5.3-0   aebe758cef4c   16 months ago   299MB
registry.cn-hangzhou.aliyuncs.com/google_containers/pause                     3.7       221177c6082a   17 months ago   711kB
registry.cn-hangzhou.aliyuncs.com/google_containers/coredns                   v1.8.6    a4ca41631cc7   22 months ago   46.8MB
k8s.gcr.io/pause                                                              3.6       6270bb605e12   24 months ago   683kB
registry.cn-hangzhou.aliyuncs.com/google_containers/storage-provisioner       v5        6e38f40d628d   2 years ago     31.5MB
org/kubernetes-leader-election-example      eval $(minikube docker-env)

Mac minikube 本地构建执行 SpringCloud-Kubernetes-Example

Mac 安装 minikube 此处不描述。
本文主要参照官方流程，依据源码构建实践示例代码。

依赖版本说明：

• docker 20.10.20
• minikube v1.28.0
• k8s 1.24.1
• maven 3.6
• jdk17
• spring-cloud-kubernetes 3.1.0-SNAPSHOT
• spring-cloud-build 4.1.0-SNAPSHOT

以上maven和jdk是必要条件，注意版本的对应

基础条件准备

• 安装maven3+环境
• 安装JDK17环境
• 启动docker
• 启动minikube minikube start

查看 minikube 访问的 docker 环境

minikube docker-env

:~$ minikube docker-env
export DOCKER_TLS_VERIFY="1"
export DOCKER_HOST="tcp://127.0.0.1:54965"
export DOCKER_CERT_PATH="~/.minikube/certs"
export MINIKUBE_ACTIVE_DOCKERD="minikube"# To point your shell to minikube's docker-daemon, run:
# eval $(minikube -p minikube docker-env)

如果本地docker没有habor等私仓环境,注意这行注释，需要让当前shell去访问minikube的docker 需要执行 eval $(minikube -p minikube docker-env)。官方文档也很细心地写明了这个指令哦，对于小白还是比较友好

指令执行后，即可在当前这个shell直接docker images看到仓库中的镜像了

以下开始执行示例项目的部署

进入example项目文件夹下，为项目创建role和role-binding

kubectl apply -f leader-role.ymlapiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:name: leaderlabels:app: kubernetes-leader-election-examplegroup: org.springframework.cloud
rules:
- apiGroups:- ""resources:- podsverbs:- watch- get
- apiGroups:- ""resources:- configmapsverbs:- watch- get- update# resourceNames:#   - <config-map name>----kubectl apply -f leader-rolebinding.ymlapiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:labels:app: kubernetes-leader-election-examplegroup: org.springframework.cloudname: leader
roleRef:apiGroup: ""kind: Rolename: leader
subjects:
- kind: ServiceAccountname: defaultapiGroup: ""

在example目录下通过maven组件构建docker镜像

./mvnw spring-boot:build-image -Dspring-boot.build-image.imageName=org/kubernetes-leader-election-example

通过以下yaml构建服务

---
apiVersion: v1
kind: List
items:- apiVersion: v1kind: Servicemetadata:labels:app: kubernetes-leader-election-examplename: kubernetes-leader-election-examplespec:ports:- name: httpport: 80targetPort: 8080selector:app: kubernetes-leader-election-exampletype: ClusterIP- apiVersion: v1kind: ServiceAccountmetadata:labels:app: kubernetes-leader-election-examplename: kubernetes-leader-election-example- apiVersion: rbac.authorization.k8s.io/v1kind: RoleBindingmetadata:labels:app: kubernetes-leader-election-examplename: kubernetes-leader-election-example:viewroleRef:kind: RoleapiGroup: rbac.authorization.k8s.ioname: namespace-readersubjects:- kind: ServiceAccountname: kubernetes-leader-election-example- apiVersion: rbac.authorization.k8s.io/v1kind: Rolemetadata:namespace: defaultname: namespace-readerrules:- apiGroups: ["", "extensions", "apps"]resources: ["configmaps", "pods", "services", "endpoints", "secrets"]verbs: ["get", "list", "watch"]- apiVersion: apps/v1kind: Deploymentmetadata:name: kubernetes-leader-election-examplespec:selector:matchLabels:app: kubernetes-leader-election-exampletemplate:metadata:labels:app: kubernetes-leader-election-examplespec:serviceAccountName: kubernetes-leader-election-examplecontainers:- name: kubernetes-leader-election-exampleimage: org/kubernetes-leader-election-example:latestimagePullPolicy: IfNotPresentreadinessProbe:httpGet:port: 8080path: /actuator/health/readinesslivenessProbe:httpGet:port: 8080path: /actuator/health/livenessports:- containerPort: 8080

将内部服务的8080映射到ClusterIP的80上，获取本机的代理地址，端口未指定所以每次启动是随机的

:~$ minikube service kubernetes-leader-election-example --url
😿  service default/kubernetes-leader-election-example has no node port
http://127.0.0.1:57562
❗  Because you are using a Docker driver on darwin, the terminal needs to be open to run it.

访问地址 http://127.0.0.1:57562 就能获取响应，由于只有一个节点，所以这个节点就是主节点

curl http://127.0.0.1:57562
I am 'kubernetes-leader-election-example-5fbf89948f-gf8gd' and I am the leader of the 'world'

增加实例数增加到2个

kubectl scale --replicas=2 deployment.apps/kubernetes-leader-election-exampleNAMESPACE     NAME                                                  READY   STATUS    RESTARTS       AGE
default       kubernetes-leader-election-example-5fbf89948f-427xs   1/1     Running   4 (25m ago)    3d21h
default       kubernetes-leader-election-example-5fbf89948f-gf8gd   1/1     Running   4 (25m ago)    3d21h

由于节点数增加，两个服务也就开始存在负载均衡的效果，依赖k8s调度，此时请求目标地址 http://127.0.0.1:57562, 请求一般都是落在从节点上，反复请求节点会交替但都是到从节点

I am 'kubernetes-leader-election-example-5fbf89948f-427xs' but I am not a leader of the 'world'
I am 'kubernetes-leader-election-example-5fbf89948f-gf8gd' but I am not a leader of the 'world'

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