Init 容器

init 模板

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: busybox
    command: ['sh','-c','echo The app is running! && sleep 3600']
  initContainers:
  - name: init-myservice
    image: busybox
    command: ['sh','-c','until nslookup myservice; do echo waiting for myservice; sleep 2;done;']
  - name: init-mydb
    image: busybox
    command: ['sh','-c','until nslookup mydb; do echo waiting for mydb; sleep 2; done;']

initC:initContainers

发生场景：

当存在一个pod里有两个服务时，需要有个先后顺序，因此可以使用initC（initContainers）来保证先后顺序的服务启动。

举个例子：

apiVersion: v1
kind: Pod
metadata:
  name: twoapp
  namespace: default
  labels:
    app: myapp
    version: v1.0
spec:
  containers:
  - name: b1
    image: nginx:latest
  - name: b2
    image: busybox:latest
    command:
      ["/bin/sh","-c","sleep 36000"]

#删除所有的pod节点
kubectl delete pods --all

#删除所有的deployment
kubectl delete deployment --all

kind: Service
apiVersion: v1
metadata:
  name: myservice
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 9376

kind: Service
apiVersion: v1
metadata:
  name: mydb
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 9377

当前kubelet拥有两个检测器，他们分别对应不通的触发器(根据触发器的结构执行进一步的动作)：

• Liveness Probe：表示container是否处于live状态。如果 LivenessProbe失败，LivenessProbe将会通知kubelet对应的container不健康了。随后kubelet将kill掉 container，并根据RestarPolicy进行进一步的操作。默认情况下LivenessProbe在第一次检测之前初始化值为 Success，如果container没有提供LivenessProbe，则也认为是Success；
• Readiness Probe：表示container是否以及处于可接受service请求的状态了。如 果ReadinessProbe失败，endpoints controller将会从service所匹配到的endpoint列表中移除关于这个container的IP地址。因此对于Service匹配到的 endpoint的维护其核心是Readiness Probe。默认Readiness的初始值是Failure，如果一个container没有提供 Readiness则被认为是Success。

Liveness Probe的种类：

• ExecAction：在container中执行指定的命令。当其执行成功时，将其退出码设置为0；
• TCPSocketAction：执行一个TCP检查使用container的IP地址和指定的端口作为socket。如果端口处于打开状态视为成功；
• HTTPGetAcction：执行一个HTTP默认请求使用container的IP地址和指定的端口以及请求的路径作为url，用户可以通过host参数设置请求的地址，通过scheme参数设置协议类型(HTTP、HTTPS)如果其响应代码在200~400之间，设为成功。

检测探针 - 就绪检测

readinessProbe-httpget

apiVersion: v1
kind: Pod
metadata:
  name: readiness-httpget-pod
  namespace: default
spec:
  containers:
  - name: readiness-httpget-container
    image: wangyanglinux/myapp:v1
    imagePullPolicy: IfNotPresent
    readinessProbe:
      httpGet:
        port: 80
        path: /index1.html
      initialDelaySeconds: 1
      periodSeconds: 3

检测探针 - 存活检测

livenessProbe-exec

apiVersion: v1
kind: Pod
metadata:
  name: liveness-exec-pod
  namespace: default
spec:
  containers:
  - name: liveness-exec-container
    image: hub.atguigu.com/library/busybox
    imagePullPolicy: IfNotPresent
    command: ["/bin/sh","-c","touch /tmp/live ; sleep 60; rm -rf /tmp/live; sleep3600"]
    livenessProbe:
      exec:
        command: ["test","-e","/tmp/live"]
      initialDelaySeconds: 1
      periodSeconds: 3

livenessProbe-httpget

apiVersion: v1
kind: Pod
metadata:
  name: liveness-httpget-pod
  namespace: default
spec:
  containers:
  - name: liveness-httpget-container
    image: hub.atguigu.com/library/myapp:v1
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    livenessProbe:
      httpGet:
        port: http
        path: /index.html
      initialDelaySeconds: 1
      periodSeconds: 3
      timeoutSeconds: 10

livenessProbe-tcp

apiVersion: v1
kind: Pod
metadata:
  name: probe-tcp
spec:
  containers:
  - name: nginx
    image: hub.atguigu.com/library/myapp:v1
    livenessProbe:
      initialDelaySeconds: 5
      timeoutSeconds: 1
      tcpSocket:
        port: 80

启动、退出动作

apiVersion: v1
kind: Pod
metadata:
  name: lifecycle-demo
spec:
  containers:
  - name: lifecycle-demo-container
    image: nginx
    lifecycle:
      postStart:
        exec:
          command: ["/bin/sh", "-c", "echo Hello from the postStart handler >/usr/share/message"]
      preStop:
        exec:
          command: ["/bin/sh", "-c", "echo Hello from the poststop handler >/usr/share/message"]