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Kubernetes

Working with Kubernetes Cluster using Kubectl Part – 11 – Probes

July 26, 2019 comments off

container-probes.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world
spec:
  replicas: 1
  selector:
    matchLabels:
      app: hello-world
  template:
    metadata:
      labels:
        app: hello-world
    spec:
      containers:
      - name: hello-world
        image: gcr.io/google-samples/hello-app:1.0
        ports:
        - containerPort: 8080
        livenessProbe:
          tcpSocket:
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 5
        readinessProbe:
          httpGet:
            path: /
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 5

Commands



#Start a watch to see the events associated with our probes.
kubectl get events --watch &
clear

#We have a single container pod app, in a Deployment that has both a liveness probe and a readiness probe
more container-probes.yaml

#Send in our deployment, after 10 seconds, our liveness and readiness probes will fail.
#The liveness probe will kill the current pod, and recreate one.
kubectl apply -f container-probes.yaml

#kill our watch
fg
ctrl+c

#We can see that our container isn't ready 0/1 and it's Restarts are increasing.
kubectl get pods

#Let's figure out what's wrong
#1. We can see in the events. The Liveness and Readiness probe failures.
#2. Under Containers, Liveness and Readiness, we can see the current configuration. And the current probe configuration. Both are pointing to 8081.
#3. Under Containers, Ready and Container Contidtions, we can see that the container isn't ready.
#3. Our Container Port is 8080, that's what we want our probes, probings. 
kubectl describe pods

#So let's go ahead and change the probes to 8080
vi container-probes.yaml

#And send that change into the API Server for this deployment.
kubectl apply -f container-probes.yaml

#Confirm our probes are pointing to the correct container port now, which is 8080.
 
#Let's check our status, a couple of things happened there.
#1. Our Deployment ReplicaSet created a NEW Pod, when we pushed in the new deployment configuration.
#2. It's not immediately ready because of our initialDelaySeconds which is 10 seconds.
#3. If we wait long enough, the livenessProbe will kill the original Pod and it will go away.
#4. Leaving us with the one pod in our Deployment's ReplicaSet
kubectl get pods 

kubectl delete deployment hello-world
Rajesh Kumar
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