deployment - 如果Kubernetes中的MaxUnavailable设置为0，则不会替换Pod

Question

我想为我的Pod进行回滚部署。我正在CI环境中使用set Image更新我的Pod。将Deployment / web文件上的maxUnavailable设置为1时，我会停机。但是当我将maxUnavailable设置为0时， pods 不会被替换并且容器/应用程序不会重新启动。

我在Kubernetes集群中也有一个节点，这是它的信息

    Allocated resources:
      (Total limits may be over 100 percent, i.e., overcommitted.)
      CPU Requests  CPU Limits  Memory Requests  Memory Limits
      ------------  ----------  ---------------  -------------
      881m (93%)    396m (42%)  909712Ki (33%)   1524112Ki (56%)
    Events:         <none>

这是完整的YAML文件。我确实有准备就绪的探针组。

            apiVersion: extensions/v1beta1
            kind: Deployment
            metadata:
              annotations:
                deployment.kubernetes.io/revision: "10"
                kompose.cmd: C:\ProgramData\chocolatey\lib\kubernetes-kompose\tools\kompose.exe
                  convert
                kompose.version: 1.14.0 (fa706f2)
                kubectl.kubernetes.io/last-applied-configuration: |
                  {"apiVersion":"extensions/v1beta1","kind":"Deployment","metadata":{"annotations":{"kompose.cmd":"C:\\ProgramData\\chocolatey\\lib\\kubernetes-kompose\\tools\\kompose.exe convert","kompose.version":"1.14.0 (fa706f2)"},"creationTimestamp":null,"labels":{"io.kompose.service":"dev-web"},"name":"dev-web","namespace":"default"},"spec":{"replicas":1,"strategy":{},"template":{"metadata":{"labels":{"io.kompose.service":"dev-web"}},"spec":{"containers":[{"env":[{"name":"JWT_KEY","value":"ABCD"},{"name":"PORT","value":"2000"},{"name":"GOOGLE_APPLICATION_CREDENTIALS","value":"serviceaccount/quick-pay.json"},{"name":"mongoCon","value":"mongodb://quickpayadmin:quickpay1234@ds121343.mlab.com:21343/quick-pay-db"},{"name":"PGHost","value":"173.255.206.177"},{"name":"PGUser","value":"postgres"},{"name":"PGDatabase","value":"quickpay"},{"name":"PGPassword","value":"z33shan"},{"name":"PGPort","value":"5432"}],"image":"gcr.io/quick-pay-208307/quickpay-dev-node:latest","imagePullPolicy":"Always","name":"dev-web-container","ports":[{"containerPort":2000}],"readinessProbe":{"failureThreshold":3,"httpGet":{"path":"/","port":2000,"scheme":"HTTP"},"initialDelaySeconds":5,"periodSeconds":5,"successThreshold":1,"timeoutSeconds":1},"resources":{"requests":{"cpu":"20m"}}}]}}}}
              creationTimestamp: 2018-12-24T12:13:48Z
              generation: 12
              labels:
                io.kompose.service: dev-web
              name: dev-web
              namespace: default
              resourceVersion: "9631122"
              selfLink: /apis/extensions/v1beta1/namespaces/default/deployments/web
              uid: 5e66f7b3-0775-11e9-9653-42010a80019d
            spec:
              progressDeadlineSeconds: 600
              replicas: 2
              revisionHistoryLimit: 10
              selector:
                matchLabels:
                  io.kompose.service: web
              strategy:
                rollingUpdate:
                  maxSurge: 1
                  maxUnavailable: 0
                type: RollingUpdate
              template:
                metadata:
                  creationTimestamp: null
                  labels:
                    io.kompose.service: web
                spec:
                  containers:
                  - env:
                    - name: PORT
                      value: "2000"

                    image: gcr.io/myimagepath/web-node
                    imagePullPolicy: Always
                    name: web-container
                    ports:
                    - containerPort: 2000
                      protocol: TCP
                    readinessProbe:
                      failureThreshold: 10
                      httpGet:
                        path: /
                        port: 2000
                        scheme: HTTP
                      initialDelaySeconds: 10
                      periodSeconds: 10
                      successThreshold: 1
                      timeoutSeconds: 10
                    resources:
                      requests:
                        cpu: 10m
                    terminationMessagePath: /dev/termination-log
                    terminationMessagePolicy: File
                  dnsPolicy: ClusterFirst
                  restartPolicy: Always
                  schedulerName: default-scheduler
                  securityContext: {}
                  terminationGracePeriodSeconds: 30
            status:
              availableReplicas: 2
              conditions:
              - lastTransitionTime: 2019-01-03T05:49:46Z
                lastUpdateTime: 2019-01-03T05:49:46Z
                message: Deployment has minimum availability.
                reason: MinimumReplicasAvailable
                status: "True"
                type: Available
              - lastTransitionTime: 2018-12-24T12:13:48Z
                lastUpdateTime: 2019-01-03T06:04:24Z
                message: ReplicaSet "dev-web-7bd498fc74" has successfully progressed.
                reason: NewReplicaSetAvailable
                status: "True"
                type: Progressing
              observedGeneration: 12
              readyReplicas: 2
              replicas: 2
              updatedReplicas: 2

我尝试使用1个副本，但仍然无法正常工作。

Answer 1

在第一种情况下，kubernetes删除一个Pod(maxUnavailable: 1)并使用新镜像启动Pod，并等待〜110秒(基于您的就绪性探针)以检查新Pod是否能够满足请求。新的Pod无法提供请求，但Pod处于运行状态，因此它将删除第二个旧Pod，并以新镜像启动它，第二个Pod再次等待准备就绪探针完成。这是在两个容器都未准备好服务请求之间以及停机之间存在一段时间的原因。

在第二个senario中，您有maxUnavailable:0，kubernetes首先用新镜像启动pod，并且它无法在约110秒内满足请求(根据您的准备情况探针)，因此超时并删除了新pod新形象。第二个 pods 也发生了同样的情况。因此，您的两个 pods 都不会更新

因此，原因是您没有给应用程序足够的时间来启动请求。因此，问题。请在准备情况调查中增加failureThreshold和maxUnavailable: 0的值，它将起作用。