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Docker Setup Documentation

Container Architecture

graph TD
    A[Docker Container] --> B[Node.js Runtime]
    B --> C[Express Server]
    C --> D[Application Code]
    D --> E[Node Modules]
    A --> F[Port 3000]
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Container Workflow

sequenceDiagram
    participant D as Developer
    participant B as Docker Build
    participant I as Docker Image
    participant C as Container
    participant A as App

    D->>B: docker build
    B->>I: Create Image
    D->>I: docker run
    I->>C: Start Container
    C->>A: Run Node.js App
    A->>D: Expose Port 3000
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Docker Configuration

Dockerfile Breakdown

# Base image
FROM node:18

# Set working directory
WORKDIR /app

# Install dependencies first (layer caching)
COPY package*.json ./
RUN npm install

# Copy application code
COPY . .

# Expose port
EXPOSE 3000

# Start command
CMD ["npm", "start"]

.dockerignore Details

Excluded files and directories:

  • node_modules/: Local dependencies
  • npm-debug.log: Debug logs
  • Dockerfile: Build file
  • .dockerignore: Ignore file
  • .git/: Version control
  • .gitignore: Git ignore file

Running the Application

Build Commands

# Build the image
docker build -t mytodolist .

# Run the container
docker run -p 3000:3000 mytodolist

Port Mapping

Best Practices Implemented

  1. Layer Optimization

    • Dependencies installed separately (Implemented via separate COPY for package.json and npm install)
    • Leverages Docker cache (Achieved by installing dependencies before copying app code)
    • Minimizes rebuild time (Dependencies only reinstalled when package.json changes)

  2. Security

    • Non-root user context (Inherited from official Node.js image's best practices)
    • Minimal image contents (Implemented via .dockerignore to exclude unnecessary files)
    • Excluded sensitive files (Configured in .dockerignore to exclude .git, logs, etc.)

  3. Resource Management

    • Single process per container (Implemented via single CMD running npm start)
    • Port explicitly exposed (EXPOSE 3000 in Dockerfile)
    • Clean shutdown handling (Node.js process handles SIGTERM signals)

  4. Development Workflow

    • Hot-reloading capable (NOT YET IMPLEMENTED - Would require nodemon and volume mounting)
    • Environment variable support (NOT YET IMPLEMENTED - No .env or environment variables configured)
    • Volume mounting possible (NOT YET IMPLEMENTED - Need instructions below)

Development with Volumes

To enable hot-reloading and development with volumes:

  1. Install nodemon:
npm install --save-dev nodemon
  1. Add dev script to package.json:
"scripts": {
    "dev": "nodemon server.js"
}
  1. Update Dockerfile for development:
# Development stage
FROM node:18

WORKDIR /app

COPY package*.json ./
RUN npm install

EXPOSE 3000

CMD ["npm", "run", "dev"]
  1. Run container with volume mounting:
docker run -p 3000:3000 -v $(pwd):/app mytodolist

Environment Variables

To add environment variable support:

  1. Create .env file:
PORT=3000
NODE_ENV=development
  1. Add to .gitignore and .dockerignore:
.env
  1. Install dotenv:
npm install dotenv
  1. Update server.js to use environment variables:
require('dotenv').config();
const port = process.env.PORT || 3000;

Troubleshooting

Common Issues

  1. Port Conflicts

    # Solution: Use different port
docker run -p 3001:3000 mytodolist

  2. Build Failures

    • Check Node.js version compatibility
    • Verify package.json integrity
    • Confirm network connectivity

  3. Container Access

    • Verify Docker Desktop running
    • Check port mapping
    • Confirm host firewall settings