124 lines
3.7 KiB
Markdown
124 lines
3.7 KiB
Markdown
# Notes App — Kubernetes Deployment
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A simple web application where you can write, view, and delete notes. Built with Flask (Python) and PostgreSQL.
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---
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## What the app does
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- Add a note using the text box on the main page
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- View all saved notes
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- Delete any note with a button click
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- Notes are stored in a PostgreSQL database and survive pod restarts
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---
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## Containers used
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| Container | Image | Description |
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|-----------|-------|-------------|
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| `notes-web` | `notes-web:latest` (built locally) | Flask web app — serves the UI and handles requests |
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| `postgres` | `postgres:15-alpine` | PostgreSQL database — stores notes |
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---
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## Kubernetes objects
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| Object | Name | Description |
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|--------|------|-------------|
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| Namespace | `notes-app` | Isolates all app objects from other workloads |
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| Deployment | `notes-web` | Runs 2 replicas of the Flask web app |
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| StatefulSet | `postgres` | Runs 1 PostgreSQL pod with stable identity |
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| PersistentVolume | `postgres-pv` | 1Gi volume backed by host path `/mnt/notes-postgres-data` |
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| PersistentVolumeClaim | `postgres-pvc` | Claims the PV for use by the StatefulSet |
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| Service (NodePort) | `notes-web-service` | Exposes the web app on port `30080` |
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| Service (ClusterIP) | `postgres-service` | Internal access to PostgreSQL for the web app |
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| Service (Headless) | `postgres-headless` | Required by the StatefulSet for stable DNS |
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---
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## Networking and volumes
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**Services:**
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- `notes-web-service` — NodePort, exposes port `30080` externally → routes to pod port `5000`
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- `postgres-service` — ClusterIP, internal only, port `5432` → the web app connects to this
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- `postgres-headless` — Headless service (no ClusterIP) used by the StatefulSet
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**Volume:**
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- `postgres-pv` uses a `hostPath` at `/mnt/notes-postgres-data` on the node
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- Data persists even if the PostgreSQL pod is restarted or recreated
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---
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## Container configuration
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**notes-web:**
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- Environment variables set the database connection: `DB_HOST`, `DB_PORT`, `DB_NAME`, `DB_USER`, `DB_PASS`
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- `imagePullPolicy: Never` — uses the locally built image (no registry needed)
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- Runs on port `5000`
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**postgres:**
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- `POSTGRES_DB`, `POSTGRES_USER`, `POSTGRES_PASSWORD` configure the database on first start
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- Data directory `/var/lib/postgresql/data` is mounted from the PVC
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---
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## How to use
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### 1. Prepare (build image, create host directory)
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```bash
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chmod +x prepare-app.sh start-app.sh stop-app.sh show-url.sh
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./prepare-app.sh
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```
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### 2. Start the application
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```bash
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./start-app.sh
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```
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### 3. Open in browser
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```bash
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http://localhost:8080/ - **Port-forwarding has been done already**
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```
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Or open manually:
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- **Minikube:** `minikube service notes-web-service -n notes-app`
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- **Other:** `http://<node-ip>:30080`
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### 4. Stop (keep objects, scale down)
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```bash
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kubectl scale deployment notes-web -n notes-app --replicas=0
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kubectl scale statefulset postgres -n notes-app --replicas=0
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```
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### 5. Delete everything
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```bash
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./stop-app.sh
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```
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---
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## File overview
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```
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z2/
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├── app/
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│ ├── app.py # Flask application
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│ ├── requirements.txt # Python dependencies
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│ └── Dockerfile # Image definition for notes-web
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├── namespace.yaml # Namespace: notes-app
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├── deployment.yaml # Deployment: notes-web (Flask)
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├── statefulset.yaml # StatefulSet + PV + PVC (PostgreSQL)
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├── service.yaml # Services: notes-web-service, postgres-service
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├── prepare-app.sh # Build image, create host directory
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├── start-app.sh # Apply all Kubernetes objects
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├── stop-app.sh # Delete all Kubernetes objects
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├── status.sh # Print the status of Namespace, PV, PVC, PODS and Services
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└── README.md # This file
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```
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