Kubernetes 0 Downtime using Readiness Probe and RollBack strategy not working

问题

I have set up a Node app on Kubernetes. I'm running a single replica and I want 0 down-time when the image is updated. I update my Pod using set Image on Kubernetes.

'set', 'image', 'deployment/dev-web'

Here's my YAML file

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  annotations:
    deployment.kubernetes.io/revision: "2"
  generation: 2
  labels:
    io.kompose.service: dev-web
  name: dev-web
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      io.kompose.service: dev-web
  strategy:
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
    type: RollingUpdate
  template:
    metadata:
      creationTimestamp: null
      labels:
        io.kompose.service: dev-web
    spec:
      containers:
      - env:
        image: gcr.io/my-project-link/my-image-link
        imagePullPolicy: Always
        name: dev-web-container
        ports:
        - containerPort: 2000
          protocol: TCP
        readinessProbe:
          failureThreshold: 3
          httpGet:
            path: /
            port: 2000
            scheme: HTTP
          initialDelaySeconds: 5
          periodSeconds: 5
          successThreshold: 1
          timeoutSeconds: 1
        resources:
          requests:
            cpu: 20m
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {}
      terminationGracePeriodSeconds: 30
status:
  availableReplicas: 1
  conditions:
  - lastTransitionTime: 2018-12-07T11:13:21Z
    lastUpdateTime: 2018-12-07T11:13:21Z
    message: Deployment has minimum availability.
    reason: MinimumReplicasAvailable
    status: "True"
    type: Available
  observedGeneration: 2
  readyReplicas: 1
  replicas: 1
  updatedReplicas: 1

My app does give 200 response on '/' get therefore Readiness Probe works but when I update the Image, and test it but continuously hitting CURL, it gives me downtime which lasts for like 20-40 seconds.

回答1:

You setup your maxUnavailable as 1 even when you have only one replica, you should be having maxUnavailable to 0.

strategy:
 type: RollingUpdate
 rollingUpdate:
   maxUnavailable: 0
   maxSurge: 1

It basically tells Kubernetes that there should be zero unavailable pods while deploying (maxUnavailable: 0) and there should be one new pod at a time (maxSurge: 1).

I am hoping you setup the readiness probe something like this:

readinessProbe:
  httpGet:
    path: /
    port: 80
  initialDelaySeconds: 5
  periodSeconds: 5
  successThreshold: 1

Basically, this is a check that Kubernetes does in order to make sure that your pod is ready to send traffic to it. Until it is not ready, Kubernetes will not use your pod.

来源：https://stackoverflow.com/questions/53668964/kubernetes-0-downtime-using-readiness-probe-and-rollback-strategy-not-working

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Kubernetes

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