李振东的blog

Pod的生命周期

1. 初始化容器
2. 两个钩子
3. 两个探针

初始化容器（initContainers）

## 初始化容器：容器启动之前，我们可以让他做一些准备工作，初始化容器执行完成后就结束退出
## 启动一个容器 挂载相同的目录 ，对目录进行操作

apiVersion: "v1"  
kind: "Pod"  
metadata:  
  name: initv2 
  namespace: default  
  labels:  
    app: nginx  
spec:  
  volumes:  
  - name: nginx-data  
    hostPath:  
      path: /data/nginx  
  
  initContainers:  
  - name: init-c  
    image: centos:7 
    imagePullPolicy: IfNotPresent  
    command: ["sh", "-c", "echo 'initContainers' > /usr/share/nginx/html/index.html"]  
    volumeMounts:  
    - name: nginx-data  
      mountPath: /usr/share/nginx/html/  
  
  containers:  
  - name: nginx  
    image: nginx:alpine  
    imagePullPolicy: IfNotPresent  
    volumeMounts:  
    - name: nginx-data  
      mountPath: /usr/share/nginx/html/

### 运行pod资源清单 查询pod详细信息
[root@master kubernetes]# kubectl apply -f initv2.yaml 
pod/initv2 created
NAME                     READY   STATUS    RESTARTS   AGE   IP          NODE   
initv2                   1/1     Running   0          38s   10.2.3.20   node03 
nginx-565785f75c-hn9ql   1/1     Running   0          22h   10.2.3.13   node03 

### 进入node 查询挂载目录情况
[root@node03 ~]# ll /data/nginx/
total 4
-rw-r--r-- 1 root root 15 Sep 20 14:30 index.html

### 检查网页
[root@master kubernetes]# curl 10.2.3.20 
initContainers

钩子（postStart）（preStop）

#### postStart ####
启动之后 执行

#### preStop ####
结束之前  执行

####  选项 ####
exec：执行命令
httpGet：检测HTTP
tcpSocket：检测端口

postStart （启动之后执行）

apiVersion: "v1"  
kind: "Pod"  
metadata:  
  name: portstart 
  namespace: default  
  labels:  
    os: c7  
spec:  
  conatiners: 
    - name: c7-container
      image: centos:7
      imagePullPolicy: IfNotPresent
      command: ["/bin/sh","-c","tail -f /etc/hosts"]
      lifecycle:
        postStart:
          exec:
            command: ["/bin/sh","-c","groupadd www -g 666 && useradd www -u 666 -g 666 "]

#### 运行 检查
[root@master kubernetes]# kubectl apply  -f portstart.yaml 
pod/portstart created

[root@master kubernetes]# kubectl exec -it portstart -- /bin/bash

[root@portstart /]# id 666
uid=666(www) gid=666(www) groups=666(www)

preStop （结束之前）

apiVersion: "v1"  
kind: "Pod"  
metadata:  
  name: prestop
  namespace: default  
  labels:  
    os: c7  
spec:  
  volumes:  
  - name: test-data  
    hostPath:  
      path: /data/test/
  
  containers:  
  - name: centos  
    image: centos:7  
    imagePullPolicy: IfNotPresent 
    command: ["/bin/sh","-c","tail -f /etc/hosts"]
    lifecycle:
      postStart:
        exec:
          command: ["/bin/sh","-c","echo helloword > /data/1.txt"]
      preStop:
        exec:
          command: ["/bin/sh","-c","echo byebye~ > /data/1.txt"]
    volumeMounts:  
    - name: nginx-data  
      mountPath: /data

#### 运行  详细信息  检查
[root@master kubernetes]# kubectl apply -f prestop.yaml 
pod/prestop created

[root@master kubernetes]# kubectl exec -it prestop -- /bin/bash

[root@prestop /]# cat /data/1.txt
helloword

[root@master kubernetes]# kubectl get pod prestop -owide
NAME      READY   STATUS    RESTARTS   AGE   IP          NODE    
prestop   1/1     Running   0          16s   10.2.3.23   node03   

----- 关闭后查看 ----

[root@master kubernetes]# kubectl delete -f prestop.yaml 
pod "prestop" deleted

[root@node03 ~]# cat /data/test/1.txt 
byebye~

探针（livenessprobe）（readnissprobe）

## 存活性探针（存活态探针）livenessprobe
用于定义容器内，应用是否满足探针指定状态，如果不满足，则删除POD重新拉起一个新的POD
存活探针简单来说就是用来检测容器的应用程序是否还正常工作，如果应用程序不正常，即使容器还活着也没
有意义了，所以这时候就可以使用存活探针来探测，如果应用程序不正常，就重启POD。

exec：执行命令
httpGet：检测HTTP
tcpSocket：检测端口

## 就绪性探针（就绪态探针）readnissprobe
有时候我们Pod本身已经起来了，但是pod的容器还没有完全准备好对外提供服务，那么这时候流量进来就会造
成请求失败的情况出现，针对这种情况k8s有一种探针叫就绪探针，他的作用就是让k8s知道你的Pod内应用是
否准备好为请求提供服务。只有就绪探针ok了才会把流量转发到pod上。
exec：执行命令
httpGet：检测HTTP
tcpSocket：检测端口


#### 参数
initialDelaySeconds: 		# 第一次执行探针需要在容器启动后等待的时候时间
periodSeconds: 				# 容器启动后每隔多少秒执行一次存活探针 默认10s
timeoutSeconds: 			# 探针超时时间，默认1秒，最小1秒
successThreshold: 			# 探针失败后最少连续探测成功多少次才被认定成功，默认1次，如果是liveness必须为1
failureThreshold: 			# 探针成功后被视为失败的探测的最小连续失败次数。默认3次。最小值为1

存活性探针（livenessprobe）

livenessprobe -- exec

### 判断返回值 $?  是否为0

##### exec(执行命令判断返回值) #####

apiVersion: "v1"  
kind: "Pod"  
metadata:  
  name: livenessprobe 
  namespace: default  
  labels:  
    app: nginx  
spec:  
  volumes:  
  - name: nginx-data  
    hostPath:  
      path: /data/nginx  
  
  containers:  
  - name: nginx  
    image: nginx:alpine  
    imagePullPolicy: IfNotPresent
    lifecycle:
      postStart:
        exec:
          command: ["/bin/sh","-c","echo '存活性探针检查' >> /usr/share/nginx/html/index.html"]
    livenessProbe:
      exec: 
        command: ["/bin/sh","-c","cat /usr/share/nginx/html/index.html"]
      initialDelaySeconds: 3
      periodSeconds: 1
      timeoutSeconds: 1
      failureThreshold: 3
    volumeMounts:  
    - name: nginx-data  
      mountPath: /usr/share/nginx/html/

##### 运行 检查  详细信息 ####
[root@master kubernetes]# kubectl apply -f exec-livenessprobe.yaml 
pod/livenessprobe created
[root@master kubernetes]# kubectl get pod livenessprobe -owide
NAME            READY   STATUS    RESTARTS   AGE   IP          NODE     NOMINATED NODE   READINESS GATES
livenessprobe   1/1     Running   0          11s   10.2.3.27   node03   <none>           <none>
[root@master kubernetes]# curl 10.2.3.27
存活性探针检查

--------------------------
--------------------------
#### 测试
[root@node03 ~]# rm /data/nginx/* -rf

[root@master kubernetes]# curl 10.2.3.27    (要快不然看不到)
<html>
<head><title>403 Forbidden</title></head>
<body>
<center><h1>403 Forbidden</h1></center>
<hr><center>nginx/1.27.1</center>
</body>
</html>
[root@master kubernetes]# curl 10.2.3.27
存活性探针检查

livenessprobe -- httpGet

#### 判断网页的状态码 是否为 200

apiVersion: "v1"  
kind: "Pod"  
metadata:  
  name: livenessprobe 
  namespace: default  
  labels:  
    app: nginx  
spec:  
  volumes:  
  - name: nginx-data  
    hostPath:  
      path: /data/nginx  
  
  containers:  
  - name: nginx  
    image: nginx:alpine  
    imagePullPolicy: IfNotPresent
    lifecycle:
      postStart:
        exec:
          command: ["/bin/sh","-c","echo '存活性探针检查' >> /usr/share/nginx/html/index.html"]
    livenessProbe:
      httpGet: 
        path: /
        port: 80
      initialDelaySeconds: 3
      periodSeconds: 1
      timeoutSeconds: 1
      failureThreshold: 3
    volumeMounts:  
    - name: nginx-data  
      mountPath: /usr/share/nginx/html/

#### 运行 详细信息 检查 ####
[root@master kubernetes]# kubectl apply -f  httpGet-livenessprobe.yaml 
pod/livenessprobe created

[root@master kubernetes]# kubectl get pod livenessprobe -owide
NAME            READY   STATUS    RESTARTS   AGE   IP          NODE     NOMINATED NODE   READINESS GATES
livenessprobe   1/1     Running   0          36s   10.2.3.28   node03   <none>           <none>

[root@master kubernetes]# curl 10.2.3.28
存活性探针检查
存活性探针检查

------
#### 测试
[root@node03 nginx]# rm index.html  -f

[root@master kubernetes]# curl 10.2.3.28
存活性探针检查

livenessprobe -- tcpSocket

#### 检查端口是否存活

apiVersion: "v1"  
kind: "Pod"  
metadata:  
  name: livenessprobe 
  namespace: default  
  labels:  
    app: nginx  
spec:  
  volumes:  
  - name: nginx-data  
    hostPath:  
      path: /data/nginx  
  
  containers:  
  - name: nginx  
    image: nginx:alpine  
    imagePullPolicy: IfNotPresent
    lifecycle:
      postStart:
        exec:
          command: ["/bin/sh","-c","echo '存活性探针检查' >> /usr/share/nginx/html/index.html"]
    livenessProbe:
      tcpSocket: 
        port: 80
      initialDelaySeconds: 3
      periodSeconds: 1
      timeoutSeconds: 1
      failureThreshold: 3
    volumeMounts:  
    - name: nginx-data  
      mountPath: /usr/share/nginx/html/

#### 运行 详细信息 检查
[root@master kubernetes]# kubectl apply -f tcpSocket-livenessprobe.yaml 
pod/livenessprobe created

[root@master kubernetes]# kubectl get pod livenessprobe -owide
NAME            READY   STATUS    RESTARTS   AGE   IP          NODE     NOMINATED NODE   READINESS GATES
livenessprobe   1/1     Running   0          10s   10.2.3.29   node03   <none>           <none>

[root@master kubernetes]# curl 10.2.3.29
存活性探针检查
存活性探针检查

------------------------------
------------------------------
#### 测试
[root@master ~]# kubectl exec -it livenessprobe -- sh
/ # vi /etc/nginx/conf.d/default.conf     （把80 端口更改为81 端口） 
/ # nginx -s reload
2024/09/20 09:21:59 [notice] 42#42: signal process started
/ # command terminated with exit code 137

 
 [root@master ~]# kubectl describe pod livenessprobe 
 Liveness probe failed: dial tcp 10.2.3.29:80: connect: connection refused
 Container nginx failed liveness probe, will be restarted


[root@master kubernetes]# curl 10.2.3.29
存活性探针检查
存活性探针检查
存活性探针检查

就绪性探针（就绪性探针）readnissprobe

readnissprobe -- exec

apiVersion: "v1"  
kind: "Pod"  
metadata:  
  name: livenessprobe 
  namespace: default  
  labels:  
    app: nginx  
spec:  
  volumes:  
  - name: nginx-data  
    hostPath:  
      path: /data/nginx  
  
  containers:  
  - name: nginx  
    image: nginx:alpine  
    imagePullPolicy: IfNotPresent
    lifecycle:
      postStart:
        exec:
          command: ["/bin/sh","-c","echo '存活性探针检查' >> /usr/share/nginx/html/index.html"]
    readinssProbe:
      exec: 
        command: ["/bin/sh","-c","cat /usr/share/nginx/html/001.txt"]
      initialDelaySeconds: 3
      periodSeconds: 1
      timeoutSeconds: 1
      failureThreshold: 3
    volumeMounts:  
    - name: nginx-data  
      mountPath: /usr/share/nginx/html/

##### 运行 详细信息  检查 
[root@master kubernetes]# kubectl apply -f exec-readnissprobe.yaml 
pod/livenessprobe created

[root@master kubernetes]# kubectl get pod livenessprobe -owide
NAME            READY   STATUS             RESTARTS   AGE   IP          NODE     
livenessprobe   0/1     CrashLoopBackOff   4          45s   10.2.3.31   node03   

[root@master kubernetes]# curl 10.2.3.31
curl: (7) Failed connect to 10.2.3.31:80; Connection refused

[root@master kubernetes]# kubectl describe pod livenessprobe 
eadiness probe failed: cat: can't open '/usr/share/nginx/html/001.txt': No such file or director
---------------------------------
---------------------------------
### 测试
[root@node03 nginx]# touch 001.txt
[root@master kubernetes]# kubectl get pod livenessprobe -owide  （要快）
NAME            READY   STATUS             RESTARTS   AGE     IP          
livenessprobe   0/1     CrashLoopBackOff   5          2m39s   10.2.3.31   
[root@master kubernetes]# kubectl get pod livenessprobe -owide
NAME            READY   STATUS    RESTARTS   AGE     IP          NODE     
livenessprobe   1/1     Running   6          3m39s   10.2.3.31   node03   

[root@master kubernetes]# curl 10.2.3.31
存活性探针检查
存活性探针检查
存活性探针检查
存活性探针检查
存活性探针检查
存活性探针检查
存活性探针检查

Pod的生命周期

初始化容器 （initContainers）

钩子 （postStart）（preStop）

postStart （启动之后执行）

preStop （结束之前）

探针 （livenessprobe） （readnissprobe）

存活性探针 （livenessprobe）

livenessprobe -- exec

livenessprobe -- httpGet

livenessprobe -- tcpSocket

就绪性探针（就绪性探针）readnissprobe

readnissprobe -- exec

初始化容器（initContainers）

钩子（postStart）（preStop）

探针（livenessprobe）（readnissprobe）

存活性探针（livenessprobe）