Kubernetes Pod的应用

基础的Pod

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apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent #镜像拉取策略：只有当镜像在本地不存在时才会拉取

具体镜像概念请阅读官方文档：https://kubernetes.io/zh-cn/docs/concepts/containers/images/

多个容器组成Pod

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apiVersion: v1
kind: Pod
metadata:
  name: nginx-tomcat
  labels:
    app: nginx
spec:
  containers: # 在同一个containers内写多个容器
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent
  - name: tomcat
    image: tomcat:latest
    imagePullPolicy: IfNotPresent

Pod内的容器共享存储

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apiVersion: v1
kind: Pod
metadata:
  name: nginx-tomcat
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent
    volumeMounts:        # nginx容器挂载卷
    - name: data         # 引用卷名为data
      mountPath: /code/  # 挂载到Pod的/code目录
 
  - name: tomcat
    image: tomcat
    imagePullPolicy: IfNotPresent
    volumeMounts:       #tomcat容器挂载卷
    - name: data         #引用卷名为data
      mountPath: /code/  #挂载到Pod的/code目录
  volumes:          #定义存储卷
  - name: data      #卷名为data
    emptyDir: {}    #pod的空目录

存储相关概念请阅读官方文档：https://kubernetes.io/zh-cn/docs/concepts/storage/storage-classes/

Pod跟宿主机共享目录

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apiVersion: v1
kind: Pod
metadata:
  name: nginx-tomcat
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent
    volumeMounts:
    - name: data
      mountPath: /code/ 
 
  - name: tomcat
    image: tomcat
    imagePullPolicy: IfNotPresent
    volumeMounts:
    - name: data
      mountPath: /code/ 

  volumes:       #定义存储卷
  - name: data   #卷名
    hostPath:
      path: /code/  #宿主机共享的路径

Pod的初始化容器

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apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  initContainers:     #在容器前整一个initContainers就是初始化容器
  - name: busybox
    image: busybox
    imagePullPolicy: IfNotPresent
    args: [/bin/sh, -c, 'echo k8s >> /usr/share/nginx/html/index.html']
    # 执行命令，和command一样，但同时存在时，args作为变量存在
    volumeMounts:
    - name: data
      mountPath: /usr/share/nginx/html/

  containers:
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent
    volumeMounts:
    - name: data
      mountPath: /usr/share/nginx/html/

  volumes:
  - name: data
    emptyDir: {}

init容器具体概念请阅读官方文档：https://kubernetes.io/zh-cn/docs/concepts/workloads/pods/init-containers/

配置 Pod 初始化 https://kubernetes.io/zh-cn/docs/tasks/configure-pod-container/configure-pod-initialization/

Pod的资源限制

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apiVersion: v1
kind: Pod
metadata:
  name: resource-demo
spec:
  containers:
  - name: resource-demo
     images: nginx
     ports:
     - containerPort: 80
     resources:
       requests:
         memory: 50Mi
         cpu: 1500m
       limits:
         memory: 100Mi
         cpu: 200m
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# 参数解释：
requests :节点所需的最⼩计算资源量，k8s调度的时候的依据值
limits :限制允许的最⼤计算资源量,真正的资源限制参数
# 数值的转换：
1 CPU = 1000m，0.5 CPU = 500m，1 Mib = 1024 Kib，1 MB = 1000 KB

Pod配置存活、就绪和启动探针

具体概念请阅读官方文档：https://kubernetes.io/zh-cn/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/

POD启动和停止钩子

PostStart（启动钩子）：在容器启动创建后立刻执行，但是时间不能太长，否则容器将不会是running状态
PreStop（停止钩子）：在容器停止被删除前执行，主要用于优雅的关闭应用程序

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apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent
    lifecycle:     #生命周期
      postStart:   #启动钩子
        exec:      #在容器运行的意思
          command: [/bin/sh, -c, 'echo k8s > /usr/share/nginx/html/index.html']
      preStop:     #停止钩子
        exec:
          command: [/bin/sh, -c, 'echo beybey > /code/stop.log']
    volumeMounts:
    - name: data
      mountPath: /code/

  volumes:
  - name: data
    hostPath:
      path: /code/

Pod的存活性探针

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apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent
    lifecycle:
      postStart:
        exec:
          command: [/bin/sh, -c, 'echo ok > /usr/share/nginx/html/index.html']
      preStop:
        exec:
          command: [/bin/sh, -c, 'echo beybey > /usr/share/nginx/html/stop.log']
    livenessProbe:   # 存活性探针
      exec:          # 在容器里运行的意思
        command:     # 执行的命令(本质是echo $? 结果非0，默认3次判断为不存活，自动重启pod)
        - /bin/bash
        - -c
        - cat /usr/share/nginx/html/index.html                      
      initialDelaySeconds: 3    # 初始化延迟3秒(因为有些服务启动慢，适当提高时间)
      periodSeconds: 3          # 每3次测试一次(默认允许失败3次，3次后重启pod)

    volumeMounts:
    - name: data
      mountPath: /usr/share/nginx/html/

  volumes:
  - name: data
    hostPath:
      path: /code/
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apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent
    lifecycle:
      postStart:
        exec:
          command: [/bin/sh, -c, 'echo ok > /usr/share/nginx/html/index.html']
      preStop:
        exec:
          command: [/bin/sh, -c, 'echo beybey > /usr/share/nginx/html/stop.log']
    livenessProbe:             # 存活性探针
      httpGet:                 # http探针
        host: www.opsape.com      # 多个域名选择指定域名检测
        path: /index.html     # 检测这个url，默认3次访问不成功就判断为不存活，自动重启pod
        port: 80               # 端口为80   
      initialDelaySeconds: 3   # 初始化延迟3秒(因为有些服务启动慢，适当提高时间)
      periodSeconds: 3         # 每3次测试一次(默认允许失败3次，3次后重启pod)

    volumeMounts:
    - name: data
      mountPath: /usr/share/nginx/html/

  volumes:
  - name: data
    hostPath:
      path: /code/
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apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent
    lifecycle:
      postStart:
        exec:
          command: [/bin/sh, -c, 'echo ok > /usr/share/nginx/html/index.html']
      preStop:
        exec:
          command: [/bin/sh, -c, 'echo beybey > /usr/share/nginx/html/stop.log']
    livenessProbe:             # 存活性探针
      tcpSocket:               # 端口探针
        port: 80               # 监听端口为80，默认3次不存在就判断为不存活，自动重启pod
      initialDelaySeconds: 3   # 初始化延迟3秒(因为有些服务启动慢，适当提高时间)
      periodSeconds: 3         # 每3次测试一次(默认允许失败3次，3次后重启pod)

    volumeMounts:
    - name: data
      mountPath: /usr/share/nginx/html/

  volumes:
  - name: data
    hostPath:
      path: /code/

Pod的就绪性探针

就绪性探针和存活性探针一样有命令、http、端口三种方式

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apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.0
    imagePullPolicy: IfNotPresent
    lifecycle:
      postStart:
        exec:
          command: [/bin/sh, -c, 'echo ok > /usr/share/nginx/html/index.html']
      preStop:
        exec:
          command: [/bin/sh, -c, 'echo beybey > /usr/share/nginx/html/stop.log']
    livenessProbe:
      httpGet:                          
        path: /index.html      
        port: 80                        
      initialDelaySeconds: 3
      periodSeconds: 3
    readinessProbe:        # 就绪性探针
      httpGet:             # http探针             
        path: /index.html  # 这个url访问成功，就说明准备就绪，k8s就会接入流量，提供给外界访问
        port: 80
      initialDelaySeconds: 30    # 初始化延迟30秒(因为有些服务启动慢，适当提高时间)
      periodSeconds: 3          # 每3次测试一次(默认允许失败3次，3次后重启pod)

    volumeMounts:
    - name: data
      mountPath: /usr/share/nginx/html/

  volumes:
  - name: data
    hostPath:
      path: /code/