zkt26/z1

Task Manager — Dockerized Web Application

A modern task management web application deployed using Docker containers. The application consists of 5 services running in isolated containers, communicating over virtual networks, with persistent storage for data durability.

Table of Contents

• Description
• Prerequisites
• Architecture
• Services
• Networks
• Volumes
• Container Configuration
• Quick Start
• Usage Instructions
• Viewing the Application
• Example Workflow
• Sources
• AI Usage Declaration

---

Description

Task Manager is a full-stack web application for creating, managing, and tracking tasks. Users can:

• Create tasks with a title and optional description
• Mark tasks as completed or reopen them
• Delete tasks they no longer need
• Filter tasks by status (All / Active / Completed)
• View statistics including total, active, and completed task counts
• Manage the database via Adminer web interface

The application uses a modern dark-themed UI served by Nginx, a Node.js/Express REST API backend, PostgreSQL for persistent data storage, and Redis for response caching.

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Prerequisites

To deploy and run this application, you need:

Software	Minimum Version	Purpose
Linux	Any modern distribution	Host operating system
Docker	20.10+	Container runtime
Docker Compose	v2.0+ (plugin)	Multi-container orchestration
bash	4.0+	Running management scripts

Verify installation:

docker --version        # Docker version 20.10+
docker compose version  # Docker Compose version v2.0+
bash --version          # GNU bash, version 4.0+

---

Architecture

┌─────────────────────────────────────────────────────────┐
│                   Docker Host                            │
│                                                          │
│  ┌──────────────── frontend-net ──────────────────┐     │
│  │                                                 │     │
│  │  ┌─────────────┐         ┌─────────────┐      │     │
│  │  │   Nginx     │         │   Adminer   │      │     │
│  │  │  (frontend) │         │  (DB UI)    │      │     │
│  │  │  :5000→:80  │         │  :5001→:5000│      │     │
│  │  └──────┬──────┘         └──────┬──────┘      │     │
│  │         │                        │              │     │
│  └─────────┼────────────────────────┼──────────────┘     │
│            │                        │                     │
│  ┌─────────┼────────────────────────┼──────────────┐     │
│  │         │     backend-net        │              │     │
│  │  ┌──────▼──────┐                 │              │     │
│  │  │  Node.js    │                 │              │     │
│  │  │   (api)     │                 │              │     │
│  │  │   :3000     │                 │              │     │
│  │  └──┬──────┬───┘                 │              │     │
│  │     │      │                     │              │     │
│  │  ┌──▼────┐ ┌▼─────────┐  ┌──────▼──────┐      │     │
│  │  │ Redis │ │PostgreSQL │  │ (Adminer    │      │     │
│  │  │ :6379 │ │  :5432    │  │  connects)  │      │     │
│  │  └───────┘ └───────────┘  └─────────────┘      │     │
│  │    📦          📦                               │     │
│  │  redisdata   pgdata                             │     │
│  └─────────────────────────────────────────────────┘     │
└──────────────────────────────────────────────────────────┘

---

Services

1. Frontend (Nginx)

• Container name: taskapp-frontend
• Image: Custom (built from frontend/Dockerfile using nginx:alpine)
• Port: 5000 (public) → 80 (container)
• Role: Serves the static HTML/CSS/JS frontend and acts as a reverse proxy, forwarding /api/ requests to the Node.js backend
• Networks: frontend-net, backend-net

2. API (Node.js / Express)

• Container name: taskapp-api
• Image: Custom (built from api/Dockerfile using node:20-alpine)
• Port: 3000 (virtual, not exposed to host)
• Role: REST API server providing CRUD operations for tasks. Connects to PostgreSQL for data persistence and Redis for response caching
• Networks: backend-net

3. PostgreSQL Database

• Container name: taskapp-postgres
• Image: postgres:16-alpine
• Port: 5432 (virtual, not exposed to host)
• Role: Primary relational database storing all task data
• Volume: taskapp-pgdata mounted at /var/lib/postgresql/data
• Networks: backend-net
• Initialization: db/init.sql is automatically executed on first run to create the tasks table

4. Redis Cache

• Container name: taskapp-redis
• Image: redis:7-alpine
• Port: 6379 (virtual, not exposed to host)
• Role: In-memory cache for API responses. Reduces database load by caching task list queries for 30 seconds. Configured with append-only persistence
• Volume: taskapp-redisdata mounted at /data
• Networks: backend-net

5. Adminer (Database Web Interface)

• Container name: taskapp-adminer
• Image: adminer:latest
• Port: 5001 (public) → 5000 (container)
• Role: Web-based database management tool. Allows direct SQL queries, table browsing, and data export
• Networks: frontend-net, backend-net

---

Networks

Network Name	Driver	Connected Services	Purpose
taskapp-frontend-net	bridge	frontend, adminer	Isolates user-facing services
taskapp-backend-net	bridge	frontend, api, postgres, redis, adminer	Connects backend services for internal communication

Why two networks?

• Services on frontend-net are publicly accessible
• Services on backend-net handle internal communication
• The frontend and adminer services bridge both networks since they need public access while communicating with backend services

---

Volumes

Volume Name	Mount Point	Service	Purpose
taskapp-pgdata	/var/lib/postgresql/data	postgres	Persists database files across container restarts
taskapp-redisdata	/data	redis	Persists Redis append-only file for cache durability

Data persistence: Stopping and restarting the application (./stop-app.sh then ./start-app.sh) preserves all data. Only ./remove-app.sh deletes the volumes.

---

Container Configuration

All containers are configured with:

• Restart policy: unless-stopped — containers automatically restart on failure or system reboot
• Health checks: PostgreSQL and Redis have health checks; the API and frontend wait for healthy dependencies before starting
• Dependencies: docker compose ensures services start in the correct order:
  1. PostgreSQL + Redis (database layer)
  2. API (depends on healthy postgres and redis)
  3. Frontend + Adminer (depends on api and postgres respectively)
• Environment variables: Database credentials and connection parameters are passed via environment variables in docker-compose.yaml

---

Quick Start

# 1. Prepare the application (build images, create networks/volumes)
./prepare-app.sh

# 2. Start the application
./start-app.sh

# 3. Open in browser
#    Task Manager: http://localhost:5000
#    Adminer:      http://localhost:5001

---

Usage Instructions

Preparing the application

./prepare-app.sh

This script builds the custom Docker images (frontend, api), and creates the required networks and volumes.

Starting the application

./start-app.sh

Starts all 5 containers in detached mode. Prints the URLs for accessing the application.

Stopping the application

./stop-app.sh

Stops all containers without removing data. Your tasks and database state are preserved in the persistent volumes.

Restarting after stop

./start-app.sh

Simply run the start script again. All your data will be intact.

Removing the application

./remove-app.sh

⚠️ Warning: This removes ALL traces of the application including:

• All containers
• All networks
• All persistent volumes (data is lost)
• All locally built images

---

Viewing the Application

Task Manager (Main Application)

• URL: http://localhost:5000
• Features: Create, complete, delete, and filter tasks

Adminer (Database Management)

• URL: http://localhost:5001
• Login credentials:
  • System: PostgreSQL
  • Server: postgres
  • Username: taskuser
  • Password: taskpass
  • Database: taskmanager

---

Example Workflow

# Prepare the application
$ ./prepare-app.sh
=============================================
  Preparing Task Manager Application...
=============================================

[1/3] Building Docker images...
      ✓ Images built successfully

[2/3] Creating networks...
      ✓ Networks created

[3/3] Creating volumes...
      ✓ Volumes created

=============================================
  ✓ Application prepared successfully!
  Run ./start-app.sh to start the application
=============================================

# Start the application
$ ./start-app.sh
=============================================
  Starting Task Manager Application...
=============================================

[1/2] Starting containers...
[2/2] Waiting for services to be ready...

=============================================
  ✓ Application is running!

  🌐 Task Manager:  http://localhost:5000
  🗄️  Adminer (DB):  http://localhost:5001
=============================================

# Open http://localhost:5000 in a web browser and work with the application
# Create tasks, mark them complete, delete them, etc.

# Stop the application (data is preserved)
$ ./stop-app.sh
=============================================
  Stopping Task Manager Application...
=============================================

  ✓ Application stopped.
  Data is preserved in persistent volumes.
  Run ./start-app.sh to restart.

# Start again - all tasks are still there!
$ ./start-app.sh

# When done, remove everything
$ ./remove-app.sh
=============================================
  Removing Task Manager Application...
=============================================

  ✓ Application completely removed.

---

Sources

1. Docker Documentation — https://docs.docker.com/
2. Docker Compose Documentation — https://docs.docker.com/compose/
3. Nginx Docker Image — https://hub.docker.com/_/nginx
4. Node.js Docker Image — https://hub.docker.com/_/node
5. PostgreSQL Docker Image — https://hub.docker.com/_/postgres
6. Redis Docker Image — https://hub.docker.com/_/redis
7. Adminer Docker Image — https://hub.docker.com/_/adminer
8. Express.js Documentation — https://expressjs.com/
9. node-postgres (pg) Documentation — https://node-postgres.com/
10. Node Redis Client — https://github.com/redis/node-redis

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Use of Artificial Intelligence

Artificial intelligence tools such as ChatGPT and Claude were used as a support tool during development for understanding Docker concepts and debugging scripts. Some configuration issues were also fixed by referring to AI. All implementation, testing, and integration were performed independently.

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Project Structure

z1/
├── docker-compose.yaml      # Main orchestration configuration
├── prepare-app.sh           # Build images, create networks/volumes
├── start-app.sh             # Start all services
├── stop-app.sh              # Stop without data loss
├── remove-app.sh            # Remove all traces
├── README.md                # This documentation
├── frontend/                # Nginx + Static frontend
│   ├── Dockerfile           # Nginx container build
│   ├── nginx.conf           # Nginx configuration
│   └── public/
│       ├── index.html       # Task Manager HTML
│       ├── style.css        # Styles (dark theme)
│       └── app.js           # Frontend JavaScript
├── api/                     # Node.js REST API
│   ├── Dockerfile           # API container build
│   ├── package.json         # Node.js dependencies
│   ├── server.js            # Express API server
│   └── db.js                # PostgreSQL connection
└── db/
    └── init.sql             # Database initialization