如果你想要从零开始搭建自己的k8s集群参考我的这篇博客，预计花费时间为1天：从零开始在ubuntu上安装和使用k8s集群及报错解决
自己搭建k8s集群的难点之一是需要3台ubuntu虚拟机，要求电脑至少10G内存：操作系统4G内存，3台虚拟机需要6G内存。
另一个难度是对初学者来说，搭建太复杂了。
如果你不想手动搭建集群，只想体验和使用kubernetes集群，推荐使用digitalocean的kubernetes集群服务，自动搭建，无需安装。
digitalocean的kubernetes集群提供3台ubuntu虚拟机(node)，每台1核CPU，2G内存，共30$一个月，体验一天只要1$。
通过我的链接在digitalocean注册的新用户，可以获得100美元的2个月使用权，相当于前2个月免费用：DigitalOcean – sign up
创建kubernetes集群后，DO会提醒你使用kubectl或者doctl操作集群，我推荐kubectl这个通用工具。
在本地linux上安装kubectl，通过 kubectl 操作 k8s 集群。
echo "deb https://mirrors.aliyun.com/kubernetes/apt/ kubernetes-xenial main" | sudo tee -a /etc/apt/sources.list.d/kubernetes.list
sudo gpg --keyserver keyserver.ubuntu.com --recv-keys BA07F4FB #对安装包进行签名
sudo gpg --export --armor BA07F4FB | sudo apt-key add -
sudo apt-get update
sudo apt install kubectl
安装完成后下载yaml配置文件到目录~/.kube，然后运行：
-> # cd ~/.kube && mv k8s-zhang0peter-kubeconfig.yaml config
-> # kubectl get nodes
NAME STATUS ROLES AGE VERSION
pool-7wa24lnka-v3sf Ready <none> 11m v1.16.2
pool-7wa24lnka-v3sq Ready <none> 11m v1.16.2
pool-7wa24lnka-v3sy Ready <none> 8m8s v1.16.2
可以看到集群的状态是Ready
部署前先创建命名空间，防止污染：
-> # kubectl create namespace flask-test
namespace/flask-test created
-> # kubectl get namespace
NAME STATUS AGE
default Active 169m
flask Active 30m
flask-test Active 65s
kube-node-lease Active 169m
kube-public Active 169m
kube-system Active 169m
部署单个 pod
编辑flask-pod.yaml文件如下：
apiVersion: v1
kind: Pod
metadata:
name: flask-pod
labels:
app: flask-helloworld
spec:
containers:
- name: flask
image: registry.cn-hangzhou.aliyuncs.com/zhang0peter/flask:v0
ports:
- containerPort: 5000
部署应用：
-> # kubectl apply -f flask-pod.yaml -n flask-test
pod/flask-pod created
-> # kubectl get pod -n flask-test
NAME READY STATUS RESTARTS AGE
flask-pod 1/1 Running 0 12s
转发端口并访问：
-> # kubectl port-forward pods/flask-pod 5000:5000 -n flask-test
Forwarding from 127.0.0.1:5000 -> 5000
Handling connection for 5000
-> % curl http://127.0.0.1:5000
hello world!
删除 Pod:
-> # kubectl delete pod flask-pod -n flask-test
pod "flask-pod" deleted
部署 Deployment
编写flask-deployment.yaml文件
apiVersion: apps/v1
kind: Deployment
metadata:
name: flask-dep
labels:
app: flask-helloworld
spec:
replicas: 2
selector:
matchLabels:
app: flask-helloworld
template:
metadata:
labels:
app: flask-helloworld
spec:
containers:
- name: flask
image: 'registry.cn-hangzhou.aliyuncs.com/zhang0peter/flask:v0'
ports:
- containerPort: 5000
部署 Deployment：
-> # kubectl apply -f flask-deployment.yaml -n flask-test
deployment.apps/flask-dep created
-> # kubectl get deploy -n flask-test
NAME READY UP-TO-DATE AVAILABLE AGE
flask-dep 2/2 2 2 12s
-> # kubectl get pod -n flask-test
NAME READY STATUS RESTARTS AGE
flask-dep-56bcc4b6c5-44gkv 1/1 Running 0 25s
flask-dep-56bcc4b6c5-kkkvl 1/1 Running 0 25s
转发端口并访问：
-> # kubectl port-forward deployment/flask-dep 5000:5000 -n flask-test
Forwarding from 127.0.0.1:5000 -> 5000
Handling connection for 5000
-> % curl http://127.0.0.1:5000
hello world!
不要删除Deployment，后面还要用。
部署负载均衡应用
编写flask-service.yaml：
apiVersion: v1
kind: Service
metadata:
name: flask-svc
labels:
app: flask-helloworld
spec:
type: LoadBalancer
ports:
- port: 80
targetPort: 5000
protocol: TCP
selector:
app: flask-helloworld
部署 LoadBalancer 负载均衡：
-> # kubectl apply -f flask-service.yaml -n flask-test
service/flask-svc created
-> # kubectl get service -n flask-test
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
flask-svc LoadBalancer 10.245.139.6 <pending> 80:32349/TCP 9s
等待约5分钟，负载均衡实现，对外暴露端口:
-> # kubectl get service -n flask-test
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
flask-svc LoadBalancer 10.245.139.6 139.59.194.75 80:32349/TCP 4m23s
-> # curl 139.59.194.75
hello world!
删除 service
-> # kubectl delete service flask-svc -n flask-test
service "flask-svc" deleted
部署结束。
参考：
- A DigitalOcean Workshop: Get Started with Containers and Kubernetes - YouTube
- Getting Started with Containers and Kubernetes: A DigitalOcean Workshop Kit DigitalOcean
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