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: 1My 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.
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: 1It 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: 1Basically, 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.