Pod的状态阶段，Pod的状态情况

Pod的状态阶段

存在以下5个阶段（phase，注意和下面状态情况的差异）：

PodPending PodPhase = "Pending"
PodRunning PodPhase = "Running"
PodSucceeded PodPhase = "Succeeded"
PodFailed PodPhase = "Failed"
PodUnknown PodPhase = "Unknown"

• Pending 创建pod的请求已经被k8s接受，但是容器并没有启动成功，可能处在：写数据到etcd，调度，pull镜像，启动容器这四个阶段中的任何一个阶段，pending伴随的事件通常会有：ADDED, Modified这两个事件的产生。
• Running pod已经绑定到node节点，并且所有的容器已经启动成功，或者至少有一个容器在运行，或者在重启中。
• Succeeded pod中的所有的容器已经正常的自行退出，并且k8s永远不会自动重启这些容器，一般会是在部署job的时候会出现。
• Failed pod中的所有容器已经终止，并且至少有一个容器已经终止于失败（退出非零退出代码或被系统停止）。
• Unknown 由于某种原因，无法获得pod的状态，通常是由于与pod的主机通信错误

Pod的状态情况

状态情况是一般是指的对pod的最后几次情况转变的记录。每个情况里 包含一个status，一个type（每个条件对应着一个类型，包含PodScheduled，Ready，Initialized，Unschedulable），一个reason。

status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: 2018-08-07T10:11:56Z
    status: "True"
    type: Initialized #每次探测时候状态情况的类型
  - lastProbeTime: null
    lastTransitionTime: 2018-08-07T10:24:18Z
    message: 'containers with unready status: [nginx2]'
    reason: ContainersNotReady
    status: "False" #如果这里为false，表示这一次的探测结果有问题，原因就是message和reason里表明的
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: 2018-08-07T10:11:56Z
    status: "True"
    type: PodScheduled

------

status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: 2018-08-05T15:36:44Z
    status: "True"
    type: Initialized
  - lastProbeTime: null
    lastTransitionTime: 2018-08-07T10:36:25Z
    status: "True"
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: 2018-08-05T15:36:44Z
    status: "True"
    type: PodScheduled
  containerStatuses:

看一个完整的

[root@k8s-master cka]# kubectl get pods nginx -o yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: 2018-08-07T10:47:43Z
  labels:
    app: nginx
  name: nginx
  namespace: default
  resourceVersion: "89685"
  selfLink: /api/v1/namespaces/default/pods/nginx
  uid: 500f5920-9a2f-11e8-8140-000c29850765
spec:
  containers:
  - image: nginx
    imagePullPolicy: Always
    name: nginx
    ports:
    - containerPort: 80
      protocol: TCP
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: default-token-gt88m
      readOnly: true
  - image: nginx
    imagePullPolicy: Always
    name: nginx2
    ports:
    - containerPort: 80
      protocol: TCP
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: default-token-gt88m
      readOnly: true
  dnsPolicy: ClusterFirst
  nodeName: k8s-node1
  restartPolicy: Always
  schedulerName: default-scheduler
  securityContext: {}
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  volumes:
  - name: default-token-gt88m
    secret:
      defaultMode: 420
      secretName: default-token-gt88m
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: 2018-08-07T10:47:43Z
    status: "True"<<<<<<<<<<<<<<<<<<<<
    type: Initialized <<<<<<<<<<<<<<<<<<<<
  - lastProbeTime: null
    lastTransitionTime: 2018-08-07T10:49:10Z
    message: 'containers with unready status: [nginx2]'
    reason: ContainersNotReady
    status: "False"<<<<<<<<<<<<<<<<<<<<
    type: Ready<<<<<<<<<<<<<<<<<<<<
  - lastProbeTime: null
    lastTransitionTime: 2018-08-07T10:47:43Z
    status: "True"<<<<<<<<<<<<<<<<<<<<
    type: PodScheduled<<<<<<<<<<<<<<<<<<<<
  containerStatuses:
  - containerID: docker://2dc78277c7664db83b06076ff48e71acde1feed51dbf81a272e8730a4ffbbf13
    image: nginx:latest
    imageID: docker-pullable://nginx@sha256:d85914d547a6c92faa39ce7058bd7529baacab7e0cd4255442b04577c4d1f424
    lastState: {}
    name: nginx
    ready: true
    restartCount: 0
    state:
      running:<<<<<<<<<<<<<<<<<<<<
        startedAt: 2018-08-07T10:47:50Z
  - containerID: docker://7da0ca7b1ea086df804228493453e88ac1c14078882e52a9bf30589e922b824f
    image: nginx:latest
    imageID: docker-pullable://nginx@sha256:d85914d547a6c92faa39ce7058bd7529baacab7e0cd4255442b04577c4d1f424
    lastState:
      terminated:
        containerID: docker://7da0ca7b1ea086df804228493453e88ac1c14078882e52a9bf30589e922b824f
        exitCode: 1
        finishedAt: 2018-08-07T10:49:10Z
        reason: Error
        startedAt: 2018-08-07T10:49:07Z
    name: nginx2
    ready: false
    restartCount: 3
    state:
      waiting:<<<<<<<<<<<<<<<<<<<<
        message: Back-off 40s restarting failed container=nginx2 pod=nginx_default(500f5920-9a2f-11e8-8140-000c29850765)
        reason: CrashLoopBackOff ####容器的state reason是kubectl get pods输出中的STATUS栏结果
  hostIP: 172.16.199.101
  phase: Running
  podIP: 10.244.1.11
  qosClass: BestEffort
  startTime: 2018-08-07T10:47:43Z
[root@k8s-master cka]# kubectl get pods nginx
NAME      READY     STATUS             RESTARTS   AGE
nginx     1/2       CrashLoopBackOff   3          2m

所以kubectl get pods里给出的status实际是pod里容器的最后state reason，并不是pod的状态