Working with Kubernetes Cluster using Kubectl Part – 11 – Probes

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
Code language: PHP (php)

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

I publish technical articles at DevOps School, travel stories at Holiday Landmark, stock market insights at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow, and SEO and digital marketing strategies at Wizbrand.