environment-variables - kubectl是否替换不更新环境变量？

Question

我在Kubernetes复制 Controller 规范中添加了一个环境变量，但是当我从该规范更新正在运行的RC时，没有向其添加环境变量。怎么会？

我根据以下规范更新了RC，从上一版开始就添加了环境变量IRON_PASSWORD，但是运行的RC并没有相应地更新kubectl replace -f docker/podspecs/web-controller.yaml:

apiVersion: v1
kind: ReplicationController
metadata:
  name: web
  labels:
    app: web
spec:
  replicas: 1
  selector:
    app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: web
        image: quay.io/aknuds1/muzhack
        # Always pull latest version of image
        imagePullPolicy: Always
        env:
        - name: APP_URI
          value: https://staging.muzhack.com
        - name: IRON_PASSWORD
          value: password
        ports:
        - name: http-server
          containerPort: 80
      imagePullSecrets:
      - name: quay.io

在根据规范更新了RC之后，看起来像这样( kubectl get pod web-scpc3 -o yaml)，请注意缺少IRON_PASSWORD:

apiVersion: v1
kind: Pod
metadata:
  annotations:
    kubernetes.io/created-by: |
      {"kind":"SerializedReference","apiVersion":"v1","reference":{"kind":"ReplicationController","namespace":"default","name":"web","uid":"c1c4185f-0867-11e6-b557-42010af000f7","apiVersion":"v1","resourceVersion":"17714"}}
    kubernetes.io/limit-ranger: 'LimitRanger plugin set: cpu request for container
      web'
  creationTimestamp: 2016-04-22T08:54:00Z
  generateName: web-
  labels:
    app: web
  name: web-scpc3
  namespace: default
  resourceVersion: "17844"
  selfLink: /api/v1/namespaces/default/pods/web-scpc3
  uid: c1c5035f-0867-11e6-b557-42010af000f7
spec:
  containers:
  - env:
    - name: APP_URI
      value: https://staging.muzhack.com
    image: quay.io/aknuds1/muzhack
    imagePullPolicy: Always
    name: web
    ports:
    - containerPort: 80
      name: http-server
      protocol: TCP
    resources:
      requests:
        cpu: 100m
    terminationMessagePath: /dev/termination-log
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: default-token-vfutp
      readOnly: true
  dnsPolicy: ClusterFirst
  imagePullSecrets:
  - name: quay.io
  nodeName: gke-staging-default-pool-f98acf11-ba7d
  restartPolicy: Always
  securityContext: {}
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  volumes:
  - name: default-token-vfutp
    secret:
      secretName: default-token-vfutp
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: 2016-04-22T09:00:49Z
    message: 'containers with unready status: [web]'
    reason: ContainersNotReady
    status: "False"
    type: Ready
  containerStatuses:
  - containerID: docker://dae22acb9f236433389ac0c51b730423ef9159d0c0e12770a322c70201fb7e2a
    image: quay.io/aknuds1/muzhack
    imageID: docker://8fef42c3eba5abe59c853e9ba811b3e9f10617a257396f48e564e3206e0e1103
    lastState:
      terminated:
        containerID: docker://dae22acb9f236433389ac0c51b730423ef9159d0c0e12770a322c70201fb7e2a
        exitCode: 1
        finishedAt: 2016-04-22T09:00:48Z
        reason: Error
        startedAt: 2016-04-22T09:00:46Z
    name: web
    ready: false
    restartCount: 6
    state:
      waiting:
        message: Back-off 5m0s restarting failed container=web pod=web-scpc3_default(c1c5035f-0867-11e6-b557-42010af000f7)
        reason: CrashLoopBackOff
  hostIP: 10.132.0.3
  phase: Running
  podIP: 10.32.0.3
  startTime: 2016-04-22T08:54:00Z

Answer 1

替换ReplicationController对象实际上并不会重新创建基础Pod，因此Pod会将规范保留在RC的先前配置中，直到需要重新创建它们为止。如果删除正在运行的Pod，则创建的替换它的新Pod将具有新的环境变量。

这就是 kubectl rolling update command的用途，也是Deployment类型被添加到Kubernetes 1.2的部分原因。