5、Kubernetes pod 探测

左手的ㄟ右手 2023-07-07 12:35 21阅读 0赞

# 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"]