k8s入门

简介

docker出现之后使用容器来部署程序的数量大大增加，容器数量越来越多，架构也越来越复杂，如何管理和编排容器就成了一个非常大的问题和挑战

k8s就是为了管理和编排容器而出现的引擎，用于容器的编排管理和扩展

核心组件

节点node：一个节点就是一个服务器或者虚拟机

pod：k8s的最小调度单元，一个或多个容器的组合，pod为其提供了一个共享环境，一般只开一个容器

Service：将一组pod封装成一个服务，应用程序通过service来获取ip访问pod，有点类似于注册中心

Ingress：管理集群外部访问内部服务的入口的，通过ingress来访问内部service

ConfigMap：相当于配置中心，比如数据库配置这样的东西放到里面

Secret：将敏感信息封装起来，会对信息base编码

volume：将持久化存储的资源挂载到磁盘或者远程存储服务上

Deployment：对pod更高的一层抽象

StatefulSet：对有状态的应用程序的高层抽象，比如数据库

架构

master-worker架构，master负责管理，worker负责工作

kubelet负责管理和维护pod

kube-proxy负责为pod提供网络代理和负载均衡

master组件

api server相当于网关，所有请求都先经过api server再继续处理

搭建环境

minikube是一个轻量级的k8s实现，可在本地计算机创建虚拟机，并部署仅包含一个节点的简单集群

kubectl命令行工具与k8s进行交互

在线环境：https://killercoda.com/playgrounds/scenario/kubernetes

我是在wsl里搭配minikube，先启动docker-desktop

然后在wsl里输入

curl -LO <https://github.com/kubernetes/minikube/releases/latest/download/minikube-linux-amd64>
sudo install minikube-linux-amd64 /usr/local/bin/minikube && rm minikube-linux-amd64

常用命令

kubectl get显示查询出的何种资源

woodq@WoodQ:~$ kubectl get nodes
NAME       STATUS   ROLES           AGE     VERSION
minikube   Ready    control-plane   8m51s   v1.32.0

运行一个pod

woodq@WoodQ:~$ kubectl run nginx --image=nginx
pod/nginx created
woodq@WoodQ:~$ kubectl get pod
NAME    READY   STATUS    RESTARTS   AGE
nginx   1/1     Running   0          25s

创建一个deployment

woodq@WoodQ:~$ kubectl create deployment nginx-deployment --image=nginx
deployment.apps/nginx-deployment created
woodq@WoodQ:~$ kubectl get deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   1/1     1            1           10s

查看replicaset，pod的副本

➜  ~ kubectl get replicaset
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-6cfb98644c   1         1         1       4m51s

查看日志

➜  ~ kubectl logs nginx

进入交互式容器

➜  ~ kubectl exec -it nginx -- /bin/bash

删除命令

➜  ~ kubectl delete deployment.apps/nginx-deployment
deployment.apps "nginx-deployment" deleted

用yaml命令创建资源

➜  ~ kubectl create -f nginx-deployment.yaml
deployment.apps/nginx-deployment created

  GNU nano 7.2  
  apiVersion: apps/v1                                    nginx-deployment.yaml                                               apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 3
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: nginx:1.25
          ports:
            - containerPort: 80

通过文件创造服务

➜  ~ kubectl create -f nginx-deployment.yaml
deployment.apps/nginx-deployment created
➜  ~ kubectl expose deployment nginx-deployment
service/nginx-deployment exposed
➜  ~ kubectl get all
NAME                                    READY   STATUS    RESTARTS   AGE
pod/nginx                               1/1     Running   0          40m
pod/nginx-deployment-55d67f7b54-p6t6h   1/1     Running   0          7s
pod/nginx-deployment-55d67f7b54-skks6   1/1     Running   0          7s
pod/nginx-deployment-55d67f7b54-tqw4f   1/1     Running   0          7s

NAME                       TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
service/kubernetes         ClusterIP   10.96.0.1      <none>        443/TCP   50m
service/nginx-deployment   ClusterIP   10.106.168.9   <none>        80/TCP    5s

NAME                               READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/nginx-deployment   3/3     3            3           7s

NAME                                          DESIRED   CURRENT   READY   AGE
replicaset.apps/nginx-deployment-55d67f7b54   3         3         3       7s

详细查看内容

➜  ~ kubectl describe service nginx-deployment
Name:              nginx-deployment
Namespace:         default
Labels:            <none>
Annotations:       <none>
Selector:          app=nginx
Type:              ClusterIP
IP Family Policy:  SingleStack
IP Families:       IPv4
IP:                10.106.168.9
IPs:               10.106.168.9
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         10.244.0.10:80,10.244.0.11:80,10.244.0.12:80
Session Affinity:  None
Events:            <none>