Dev

.gitignore

@@ -0,0 +1,28 @@
+# Environment variables
+.env
+.env.*
+*.env
+
+# Kubernetes secrets
+k8s/**/secret*.yaml
+**/secrets/*.yaml
+
+# Logs
+**/logs
+*.log
+
+# Node
+node_modules/
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# IDE
+.vscode/
+.idea/
+
+# OS specific
+.DS_Store
+Thumbs.db
+
+www

K8s-trobuleshooting-guide.md

@@ -0,0 +1,227 @@
+# Kubernetes 3-Tier Application Troubleshooting Guide
+
+This document covers common issues, troubleshooting steps, and solutions when deploying a 3-tier application (Frontend, Backend, Database) to Kubernetes.
+
+## Architecture Overview
+
+Our application consists of:
+
+- **Frontend**: NGINX serving static files and proxying API requests
+- **Backend**: Node.js Express service connecting to PostgreSQL
+- **Database**: PostgreSQL storing application data
+
+## Common Issues and Solutions
+
+### 1. NGINX Host Resolution Failure
+
+#### Error
+```
+[emerg] host not found in upstream "backend" in /etc/nginx/conf.d/default.conf:14
+```
+
+#### Root Cause
+NGINX is configured to proxy requests to a host named `backend`, but the Kubernetes service providing that backend has a different name (`backend-service`).
+
+#### Solution Options
+
+**Option 1**: Rename the service to match NGINX configuration
+```yaml
+apiVersion: v1
+kind: Service
+metadata:
+  name: backend  # Changed from backend-service
+spec:
+  selector:
+    app: backend
+  ports:
+    - port: 3000
+```
+
+**Option 2**: Update NGINX configuration to use the correct service name
+```
+# In NGINX default.conf, change
+proxy_pass http://backend;
+# to
+proxy_pass http://backend-service:3000;
+```
+
+**Prevention Tip**: Always ensure service names in Kubernetes match exactly what's expected in application configurations.
+
+### 2. Database Authentication Failure
+
+#### Error
+```
+Error fetching messages: error: password authentication failed for user "postgres"
+```
+
+#### Root Cause
+Environment variable naming mismatch between container conventions:
+- PostgreSQL container uses `POSTGRES_PASSWORD`
+- Node.js app uses `DB_PASSWORD`
+
+#### Solution
+Update the Kubernetes Secret to include variables for both naming conventions:
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: db-credentials
+type: Opaque
+stringData:
+  # For PostgreSQL container
+  POSTGRES_USER: "postgres"
+  POSTGRES_PASSWORD: "secret_password"
+  POSTGRES_DB: "messages"
+  # For Node.js application
+  DB_USER: "postgres"
+  DB_PASSWORD: "secret_password"
+  DB_NAME: "messages"
+```
+
+**Prevention Tip**: When connecting different systems, be aware that environment variable conventions may differ between applications.
+
+### 3. Missing Database Schema/Tables
+
+#### Error
+```
+Error: relation "messages" does not exist
+```
+
+#### Root Cause
+When migrating from Docker Compose to Kubernetes, database initialization scripts aren't automatically carried over. In Docker Compose, initialization scripts in the `./database` directory might be automatically mounted to `/docker-entrypoint-initdb.d/` where PostgreSQL executes them.
+
+#### Solution
+1. Create a ConfigMap for database initialization:
+
+```yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: postgres-init-scripts
+data:
+  init.sql: |
+    CREATE TABLE IF NOT EXISTS messages (
+        id SERIAL PRIMARY KEY,
+        author VARCHAR(100) NOT NULL,
+        content TEXT NOT NULL,
+        created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
+    );
+
+    INSERT INTO messages (author, content) VALUES
+    ('System', 'Welcome to the message board!');
+```
+
+2. Mount the ConfigMap to the database container:
+
+```yaml
+spec:
+  template:
+    spec:
+      containers:
+      - name: database
+        # ...
+        volumeMounts:
+        - name: postgres-data
+          mountPath: /var/lib/postgresql/data
+        - name: postgres-init-scripts
+          mountPath: /docker-entrypoint-initdb.d
+      volumes:
+      - name: postgres-init-scripts
+        configMap:
+          name: postgres-init-scripts
+```
+
+**Prevention Tip**: Always consider database initialization when migrating to Kubernetes. PostgreSQL only runs initialization scripts on first startup with an empty data directory.
+
+## Port Forwarding in k3d
+
+When using k3d (Kubernetes in Docker), additional port mapping is needed to access NodePort services from the host.
+
+#### Solution Options
+
+**Option 1**: Create cluster with port mapping
+```bash
+k3d cluster create myapp --api-port 6550 -p "30080:30080@loadbalancer"
+```
+
+**Option 2**: Update existing cluster
+```bash
+docker stop k3d-myapp-serverlb
+docker update --publish 30080:30080 k3d-myapp-serverlb
+docker start k3d-myapp-serverlb
+```
+
+**Option 3**: Use kubectl port-forward
+```bash
+kubectl port-forward svc/frontend-service 8080:80
+```
+
+## Useful Troubleshooting Commands
+
+### Service and Pod Status
+```bash
+# List all pods and their status
+kubectl get pods
+
+# List all services
+kubectl get svc
+
+# Get detailed information about a pod
+kubectl describe pod <pod-name>
+```
+
+### Log Inspection
+```bash
+# View logs for a specific pod
+kubectl logs <pod-name>
+
+# View logs for all pods with a specific label
+kubectl logs -l app=backend
+
+# Stream logs in real-time
+kubectl logs -f <pod-name>
+```
+
+### Container Debugging
+```bash
+# Execute a command in a pod
+kubectl exec -it <pod-name> -- <command>
+
+# Get a shell in a pod
+kubectl exec -it <pod-name> -- bash
+
+# Check environment variables
+kubectl exec -it <pod-name> -- env
+```
+
+### Testing Connectivity
+```bash
+# Test connectivity between pods
+kubectl exec -it <source-pod> -- curl <destination-service>
+
+# Test DNS resolution
+kubectl exec -it <pod-name> -- nslookup <service-name>
+```
+
+## Common Kubernetes Gotchas
+
+1. **Volume Persistence**: StatefulSet PVCs persist data even when pods are deleted. If you need a fresh database, you must delete the PVC.
+
+2. **Namespace Isolation**: Services from different namespaces aren't directly accessible. Use fully-qualified names (`service.namespace.svc.cluster.local`).
+
+3. **Image Pull Policy**: With local development, use `imagePullPolicy: IfNotPresent` or `Never` to use locally built images.
+
+4. **Init Containers**: Consider using init containers for database schema initialization rather than relying on PostgreSQL's init scripts.
+
+5. **Health Checks**: Implement readiness and liveness probes to ensure application availability and proper rolling updates.
+
+## Conclusion
+
+Most issues when moving to Kubernetes revolve around:
+- Service discovery and naming
+- Environment variable configuration
+- Volume management and persistence
+- Container initialization
+
+By methodically troubleshooting these areas, most application deployment issues in Kubernetes can be resolved.

backend/server.js

@@ -24,11 +24,11 @@ app.use(express.json());
 
 // Database connection
 const pool = new Pool({
-    host: process.env.DB_HOST || 'localhost',
-    port: process.env.DB_PORT || 5432,
-    user: process.env.DB_USER || 'postgres',
-    password: process.env.DB_PASSWORD || 'postgres',
-    database: process.env.DB_NAME || 'messages'
+    host: process.env.DB_HOST,
+    port: process.env.DB_PORT,
+    user: process.env.DB_USER,
+    password: process.env.DB_PASSWORD,
+    database: process.env.DB_NAME
 });
 
 // Simple logging middleware

k8s/backend.yaml

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+apiVersion: v1
+kind: Service
+metadata:
+  name: backend
+spec:
+  selector:
+    app: backend
+  ports:
+    - port: 3000
+---
+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: k3d-myapp-backend:latest
+        imagePullPolicy: IfNotPresent
+        envFrom:
+        - configMapRef:
+            name: app-config
+        - secretRef:
+            name: db-credentials

k8s/configmap.yaml

@@ -0,0 +1,9 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: app-config
+data:
+  NODE_ENV: "development"
+  API_PORT: "3000"
+  DB_HOST: "database-service"
+  DB_PORT: "5432"

k8s/database.yaml

@@ -0,0 +1,48 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: database-service
+spec:
+  selector:
+    app: database
+  ports:
+    - port: 5432
+---
+apiVersion: apps/v1
+kind: StatefulSet
+metadata:
+  name: database
+spec:
+  serviceName: database-service
+  replicas: 1
+  selector:
+    matchLabels:
+      app: database
+  template:
+    metadata:
+      labels:
+        app: database
+    spec:
+      containers:
+      - name: database
+        image: postgres:13
+        envFrom:
+        - secretRef:
+            name: db-credentials
+        volumeMounts:
+        - name: postgres-data
+          mountPath: /var/lib/postgresql/data
+        - name: postgres-init-scripts
+          mountPath: /docker-entrypoint-initdb.d
+      volumes:
+      - name: postgres-init-scripts
+        configMap:
+          name: postgres-init-scripts
+  volumeClaimTemplates:
+  - metadata:
+      name: postgres-data
+    spec:
+      accessModes: [ "ReadWriteOnce" ]
+      resources:
+        requests:
+          storage: 1Gi