Pod生命周期
1. Pod生命周期过程中的状态（或者叫相位）
- [x] Pending: API Server创立了pod资源对象并存入etcd，但未被调度实现或仍处于下载镜像过程
- [x] Running: pod已被调度至节点，并且所有容器都被kubelet创立实现
- [x] Succeeded: pod中的所有容器都曾经胜利终止并且不会被重启
- [x] Failed: 所有容器曾经被终止，但至多有一个容器终止失败，即容器返回非0值的退出状态或被已被零碎终止
- [x] Unknown: API Server无奈失常获取到pod对象状态信息，通常是因为其无奈与所在工作节点的kubelet通信所致
2.Pod创立过程
3.针对pod生命周期，做一些事先，事中，预先的一些操作
- 初始化容器
- 生命周期钩子函数
- 容器探测
3.1 初始化容器
$ cat initC-pod.yamlapiVersion: v1kind: Podmetadata: name: myapp-pod labels: app: myappspec: containers: - name: myapp-container image: busybox:1.28 command: ['sh', '-c', 'echo The app is running! && sleep 3600'] initContainers: - name: init-myservice image: busybox:1.28 command: ['sh', '-c', "until nslookup myservice.$(cat /var/run/secrets/kubernetes.io/serviceaccount/namespace).svc.cluster.local; do echo waiting for myservice; sleep 2; done"] - name: init-mydb image: busybox:1.28 command: ['sh', '-c', "until nslookup mydb.$(cat /var/run/secrets/kubernetes.io/serviceaccount/namespace).svc.cluster.local; do echo waiting for mydb; sleep 2; done"]$ cat initC-service.yamlkind: ServiceapiVersion: v1metadata: name: myservicespec: ports: - protocol: TCP port: 80 targetPort: 9367---kind: ServiceapiVersion: v1metadata: name: mydbspec: ports: - protocol: TCP port: 80 targetPort: 9377创立pod，不创立service，pod在初始化时查看域名失败，容器会停留在init状态
$ kubectl apply -f initC-pod.yaml $ kubectl get podNAME READY STATUS RESTARTS AGEmyapp-pod 0/1 Init:0/2 0 7s$ kubectl describe -f initC-pod.yaml... init-myservice: Container ID: docker://c22ec8d0b0ab5cb9a55274892ae7f818198394f9fb851cf672b60dc30099df1f Image: busybox Image ID: docker-pullable://busybox@sha256:9ddee63a712cea977267342e8750ecbc60d3aab25f04ceacfa795e6fce341793 Port: <none> Host Port: <none> Command: sh -c until nslookup myservice; do echo waiting for myservice; sleep 2; done; State: Running Started: Sun, 19 Jul 2020 13:54:43 +0800 Ready: False Restart Count: 0 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-58nkl (ro) init-mydb: Container ID: Image: busybox Image ID: Port: <none> Host Port: <none> Command: sh -c until nslookup mydb; do echo waiting for mydb; sleep 2; done; State: Waiting Reason: PodInitializing Ready: False Restart Count: 0 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-58nkl (ro)...$ kubectl logs myapp-pod -c init-myservicnslookup: can't resolve 'myservice.default.svc.cluster.local'Server: 10.96.0.10Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local$ kubectl logs myapp-pod -c init-mydbError from server (BadRequest): container "init-mydb" in pod "myapp-pod" is waiting to start: PodInitializing创立service,service创立实现后，再看pod状态
$ kubectl create -f initC-service.yaml$ kubectl logs myapp-pod -c init-myservicwaiting for myserviceServer: 10.96.0.10Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.localName: myservice.default.svc.cluster.localAddress 1: 10.100.169.77 myservice.default.svc.cluster.local$ kubectl logs myapp-pod -c init-mydbServer: 10.96.0.10Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.localName: mydb.default.svc.cluster.localAddress 1: 10.111.35.232 mydb.default.svc.cluster.local$ kubectl get podNAME READY STATUS RESTARTS AGEmyapp-pod 1/1 Running 0 21m