Pod中的钩子分为启动后钩子post start hook和结束前钩子pre stop hook。

  • post start hook：主要是为了容器启动后做一些初始化工作。只有post start hook启动成功了main container才能正常工作。
  • pre stop hook：一般在主进程结束之前做一些清理操作。清理操作可能会有一些要求，只有清理完成了pod才会终止，所以一定要确保pre stop hook的任务正常结束了，容器才能正常结束。

pod钩子示例

1.编写资源清单

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
root@k8s-master01:~/yaml/chapter04# kubectl apply -f lifecycle-demo.yaml
apiVersion: v1
kind: Pod
metadata:
  name: lifecycle-demo
  namespace: default
spec:
  containers:
  - name: demo
    image: ikubernetes/demoapp:v1.0
    imagePullPolicy: IfNotPresent
    securityContext:
      capabilities:
        add:
        - NET_ADMIN
    livenessProbe:
      httpGet:
        path: '/livez'
        port: 80
        scheme: HTTP
      initialDelaySeconds: 5
    lifecycle:
      postStart:
        exec:
          command: ['/bin/sh','-c','iptables -t nat -A PREROUTING -p tcp --dport 8080 -j REDIRECT --to-ports 80']
      preStop:
        exec:
          command: ['/bin/sh','-c','while killall python3; do sleep 1; done']
  restartPolicy: Always

2.应用清单文件

1
2
3
4
5
6
7
root@k8s-master01:~/yaml/chapter04# kubectl apply -f lifecycle-demo.yaml
pod/lifecycle-demo created

# 已经运行说名内部命令已经启动成功
root@k8s-master01:~/yaml/chapter04# kubectl get pods lifecycle-demo -o wide
NAME             READY   STATUS    RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES
lifecycle-demo   1/1     Running   0          67s   10.244.2.22   k8s-node02   <none>           <none>

3.测试

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
# 进入容器验证iptables规则
root@k8s-master01:~/yaml/chapter04# kubectl exec lifecycle-demo -- iptables -t nat -nvL
Chain PREROUTING (policy ACCEPT 53 packets, 3180 bytes)
 pkts bytes target     prot opt in     out     source               destination
    0     0 REDIRECT   tcp  --  *      *       0.0.0.0/0            0.0.0.0/0            tcp dpt:8080 redir ports 80

Chain INPUT (policy ACCEPT 53 packets, 3180 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination
 
 # 访问8080端口测试
root@k8s-master01:~/yaml/chapter04# curl 10.244.2.22:8080
iKubernetes demoapp v1.0 !! ClientIP: 10.244.0.0, ServerName: lifecycle-demo, ServerIP: 10.244.2.22!