Add Kubernetes troubleshooting scenario for application not accessible due to Secret and Service misconfiguration

README.md

@@ -8,7 +8,7 @@ This is the repository for the scenarios available on [killercoda.com/kubernetes
 * StatefulSet
 * kubectl intro
 * kubectl contexts
-* ...
+* Kubernetes troubleshooting scenario
 
 ## Contribute
 

application-troubleshooting/README.md

@@ -0,0 +1 @@
+- Troubleshoot application not accessible due to Secret misconfiguration and Service port mismatch

application-troubleshooting/app-not-accessible/intro.md

@@ -0,0 +1,37 @@
+# Troubleshoot Application Not Accessible in Kubernetes
+
+An application has been deployed to the Kubernetes cluster, but it is not accessible.
+
+Although all required resources exist, the application is not functioning as expected.
+
+Your task is to investigate and fix the issues step by step.
+
+---
+
+## Observed Problems
+
+- The backend pod is stuck in `CrashLoopBackOff`
+- A Service exists for the application
+- Accessing the application through the Service fails
+
+---
+
+## Tasks
+
+1. Investigate why the pod is crashing and fix the issue.
+2. Ensure the pod reaches the `Running` state.
+3. Investigate why the Service is not routing traffic correctly.
+4. Fix the Service configuration so the application becomes accessible.
+
+---
+
+## Useful Commands
+
+```bash
+kubectl get pods -n app-demo
+kubectl describe pod <pod-name> -n app-demo
+kubectl logs <pod-name> -n app-demo
+
+kubectl get svc -n app-demo
+kubectl describe svc backend-svc -n app-demo
+kubectl port-forward svc/backend-svc 8080:80 -n app-demo

application-troubleshooting/app-not-accessible/setup.sh

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+#! /bin/bash
+set -e
+kubectl create namespace app-demo || true
+
+kubectl apply -n app-demo -f - <<EOF
+apiVersion: v1
+kind: Secret
+metadata:
+  name: app-secret
+type: Opaque
+stringData:
+  DB_PASSWORD: supersecret
+EOF
+
+kubectl apply -n app-demo -f - <<EOF
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: backend
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: backend
+  template:
+    metadata:
+      labels:
+        app: backend
+    spec:
+      containers:
+      - name: backend
+        image: hashicorp/http-echo
+        args:
+          - "-text=Backend running"
+          - "-listen=:8080"
+        env:
+        - name: DB_PASSWORD
+          valueFrom:
+            secretKeyRef:
+              name: app-secret
+              key: DB_PASS
+        ports:
+        - containerPort: 8080
+EOF
+
+kubectl apply -n app-demo -f - <<EOF
+apiVersion: v1
+kind: Service
+metadata:
+  name: backend-svc
+spec:
+  selector:
+    app: backend
+  ports:
+  - port: 80
+    targetPort: 80
+EOF

application-troubleshooting/app-not-accessible/verify.sh

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+#!/bin/bash
+set -e
+
+NAMESPACE="app-demo"
+APP_LABEL="backend"
+SERVICE_NAME="backend-svc"
+
+# 1) Verify the backend pod is Running
+POD_PHASE=$(kubectl get pods -n "$NAMESPACE" -l app="$APP_LABEL" \
+  -o jsonpath='{.items[0].status.phase}')
+
+if [ "$POD_PHASE" != "Running" ]; then
+  echo "❌ Backend pod is not running. Current phase: $POD_PHASE"
+  exit 1
+fi
+
+# 2) Verify the Service targetPort is correctly set to 8080
+TARGET_PORT=$(kubectl get svc "$SERVICE_NAME" -n "$NAMESPACE" \
+  -o jsonpath='{.spec.ports[0].targetPort}')
+
+if [ "$TARGET_PORT" != "8080" ]; then
+  echo "❌ Service targetPort is incorrect. Expected 8080, got $TARGET_PORT"
+  exit 1
+fi
+
+echo "✅ Application is running and Service is configured correctly."