fayz131 · fayz131 · Mar 27, 2026
diff --git a/labs/lab09/README.md b/labs/lab09/README.md
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+# Lab 09 — Kubernetes Fundamentals
+
+## Architecture Overview
+
+This lab demonstrates deployment of a containerized FastAPI application to a local Kubernetes cluster using declarative manifests.
+
+Architecture:
+- 1 Kubernetes Deployment: `devops-info-service`
+- 1 Kubernetes Service: `devops-info-service`
+- 3 replicas initially, later scaled to 5 replicas
+- Service type: `NodePort`
+
+Traffic flow:
+Client -> Service -> Pods
+
+The application container listens on port `5000`.
+The Kubernetes Service exposes port `80` and forwards traffic to container port `5000`.
+
+Resource allocation strategy:
+- CPU request: `100m`
+- CPU limit: `200m`
+- Memory request: `128Mi`
+- Memory limit: `256Mi`
+
+This configuration provides basic resource isolation and helps Kubernetes schedule Pods properly.
+
+## Manifest Files
+
+### `k8s/deployment.yml`
+This manifest defines the application Deployment.
+
+Key configuration choices:
+- `replicas: 3` for high availability
+- `RollingUpdate` strategy with:
+  - `maxSurge: 1`
+  - `maxUnavailable: 0`
+- container image: `fayzullin/devops-info-service:latest`
+- container port: `5000`
+- readiness and liveness probes using `/health`
+- resource requests and limits
+- labels for organization and selector matching
+
+Why these values were chosen:
+- 3 replicas satisfy the lab requirement and improve availability
+- rolling update settings ensure zero downtime during updates
+- resource limits protect the cluster from excessive resource usage
+- `/health` is the dedicated endpoint for health checks
+
+### `k8s/service.yml`
+This manifest defines a Kubernetes Service for exposing the application.
+
+Key configuration choices:
+- Service type: `NodePort`
+- Service port: `80`
+- target port: `5000`
+- selector: `app=devops-info-service`
+
+Why this was chosen:
+- `NodePort` is appropriate for local cluster access
+- the selector matches Pods created by the Deployment
+
+## Deployment Evidence
+
+### Cluster setup
+```bash
+kubectl cluster-info
+kubectl get nodes
+kubectl get namespaces
+```
+
+Example output:
+
+Kubernetes control plane is running at https://127.0.0.1:39539
+CoreDNS is running at https://127.0.0.1:39539/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
+
+NAME                 STATUS   ROLES           AGE   VERSION
+lab9-control-plane   Ready    control-plane   28m   v1.33.1
+
+NAME                 STATUS   AGE
+default              Active   28m
+kube-node-lease      Active   28m
+kube-public          Active   28m
+kube-system          Active   28m
+local-path-storage   Active   27m
+
+Current resources
+
+```bash
+kubectl get all
+kubectl get pods,svc -o wide
+kubectl describe deployment devops-info-service
+```
+
+Example output:
+
+NAME                                       READY   STATUS    RESTARTS   AGE
+pod/devops-info-service-7c94bcb745-dbdmp   1/1     Running   0          31s
+pod/devops-info-service-7c94bcb745-h9248   1/1     Running   0          52s
+pod/devops-info-service-7c94bcb745-rv99s   1/1     Running   0          43s
+
+NAME                          TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
+service/devops-info-service   NodePort    10.96.89.151   <none>        80:30080/TCP   7m1s
+
+NAME                                  READY   UP-TO-DATE   AVAILABLE   AGE
+deployment.apps/devops-info-service   3/3     3            3           7m2s
+Application verification
+
+The application was tested using port forwarding:
+
+```bash
+kubectl port-forward service/devops-info-service 8080:80
+curl http://localhost:8080
+curl http://localhost:8080/health
+```
+
+Example output:
+
+{"service":{"name":"devops-info-service","version":"1.0.0","description":"DevOps course info service","framework":"FastAPI"},"system":{"hostname":"devops-info-service-7c94bcb745-h9248","platform":"Linux","platform_version":"6.14.0-35-generic","architecture":"x86_64","cpu_count":6,"python_version":"3.12.13"},"runtime":{"uptime_seconds":71,"uptime_human":"0 hours, 1 minutes","current_time":"2026-03-27T17:31:04.829259+00:00","timezone":"UTC"},"request":{"client_ip":"127.0.0.1","user_agent":"curl/8.5.0","method":"GET","path":"/"},"endpoints":[{"path":"/","method":"GET","description":"Service information"},{"path":"/health","method":"GET","description":"Health check"}]}
+{"status":"healthy","timestamp":"2026-03-27T17:31:04.956924+00:00","uptime_seconds":71}
+
+## Operations Performed
+Deployment
+
+```bash
+kubectl apply -f k8s/deployment.yml
+kubectl apply -f k8s/service.yml
+Scaling demonstration
+```
+
+The Deployment was scaled from 3 replicas to 5 replicas.
+
+Commands used:
+
+```bash
+kubectl scale deployment/devops-info-service --replicas=5
+kubectl get pods
+kubectl rollout status deployment/devops-info-service
+kubectl get deployment devops-info-service
+```
+
+Result:
+
+NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
+devops-info-service   5/5     5            5           10m
+Rolling update demonstration
+
+A rolling update was demonstrated by applying an updated Deployment manifest with new probe configuration.
+
+Commands used:
+
+```bash
+kubectl apply -f deployment.yml
+kubectl rollout status deployment/devops-info-service
+kubectl describe deployment devops-info-service
+```
+
+Observed behavior:
+
+Kubernetes created a new ReplicaSet
+old Pods were terminated gradually
+new Pods became Ready before old Pods were fully removed
+zero downtime was preserved because maxUnavailable: 0
+
+## Rollback demonstration
+
+Rollback was demonstrated using Deployment rollout undo.
+
+Commands used:
+
+```bash
+kubectl rollout history deployment/devops-info-service
+kubectl rollout undo deployment/devops-info-service
+kubectl rollout status deployment/devops-info-service
+kubectl rollout history deployment/devops-info-service
+kubectl get pods
+```
+
+Example output:
+
+REVISION  CHANGE-CAUSE
+1         <none>
+2         <none>
+
+deployment.apps/devops-info-service rolled back
+
+REVISION  CHANGE-CAUSE
+2         <none>
+3         <none>
+
+Rollback result:
+
+deployment was successfully rolled back
+previous ReplicaSet became active again
+Pods were recreated and reached Running state
+
+## Production Considerations
+Health checks
+
+Both readiness and liveness probes were configured to use the /health endpoint.
+
+Why:
+
+readinessProbe ensures traffic is routed only to healthy Pods
+livenessProbe allows Kubernetes to restart unhealthy containers automatically
+Resource limits
+
+CPU and memory requests/limits were defined to:
+
+help Kubernetes scheduler place Pods correctly
+prevent one container from consuming too many cluster resources
+improve cluster stability
+Production improvements
+
+For a real production environment, I would additionally implement:
+
+Ingress or Gateway API for HTTP routing
+TLS termination
+ConfigMaps and Secrets
+Horizontal Pod Autoscaler
+PodDisruptionBudget
+centralized logging
+monitoring with Prometheus and Grafana
+CI/CD pipeline for automated deployments
+separate namespaces for environments
+Monitoring and observability strategy
+
+A production setup should include:
+
+metrics collection
+application logs aggregation
+Kubernetes events monitoring
+alerting on failed Pods, restart loops, and probe failures
+dashboarding for CPU, memory, and request latency
+
+##Challenges & Solutions
+
+Challenge 1: Docker image push failed
+
+Initially, pushing the Docker image to Docker Hub failed due to insufficient token scopes.
+
+Solution:
+
+re-authenticated with Docker Hub
+pushed the image successfully after fixing credentials
+Challenge 2: Local Kubernetes tool setup
+
+minikube was not installed on the system.
+
+Solution:
+
+installed kind
+created a local cluster with kind create cluster --name lab9
+Challenge 3: Initial Pod startup
+
+At first, Pods were in ContainerCreating and one Pod briefly showed ErrImagePull.
+
+Solution:
+
+verified the image was available in Docker Hub
+waited for image pull to complete
+confirmed all Pods eventually reached Running
+Challenge 4: Choosing correct health check endpoint
+
+Initially probes were configured against /.
+
+Solution:
+
+updated both liveness and readiness probes to use /health
+applied the updated Deployment
+verified successful rollout
+
+## What I Learned
+
+In this lab I learned:
+
+how to deploy a containerized application to Kubernetes using declarative YAML manifests
+how Deployments manage desired state and rolling updates
+how Services provide stable networking for Pods
+how to configure health checks and resource limits
+how to scale applications and perform rollback operations
+how Kubernetes reconciles desired and actual cluster state
diff --git a/labs/lab09/k8s/deployment.yml b/labs/lab09/k8s/deployment.yml
@@ -0,0 +1,46 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: devops-info-service
+  labels:
+    app: devops-info-service
+spec:
+  replicas: 3
+  strategy:
+    type: RollingUpdate
+    rollingUpdate:
+      maxSurge: 1
+      maxUnavailable: 0
+  selector:
+    matchLabels:
+      app: devops-info-service
+  template:
+    metadata:
+      labels:
+        app: devops-info-service
+    spec:
+      containers:
+        - name: devops-info-service
+          image: fayzullin/devops-info-service:latest
+          imagePullPolicy: Always
+          ports:
+            - containerPort: 5000
+          resources:
+            requests:
+              cpu: "100m"
+              memory: "128Mi"
+            limits:
+              cpu: "200m"
+              memory: "256Mi"
+          readinessProbe:
+            httpGet:
+              path: /health
+              port: 5000
+            initialDelaySeconds: 5
+            periodSeconds: 5
+          livenessProbe:
+            httpGet:
+              path: /health
+              port: 5000
+            initialDelaySeconds: 10
+            periodSeconds: 10
diff --git a/labs/lab09/k8s/service.yml b/labs/lab09/k8s/service.yml
@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: devops-info-service
+  labels:
+    app: devops-info-service
+spec:
+  type: NodePort
+  selector:
+    app: devops-info-service
+  ports:
+    - protocol: TCP
+      port: 80
+      targetPort: 5000
+      nodePort: 30080