Have you worked with Docker? Explain containerization.

Yes, Docker is essential for modern .NET Core application deployment.

Containerization is a lightweight virtualization method that packages an application and all its dependencies into a standardized unit called a container.

Key Concepts:

Container vs Virtual Machine:

• VM: Includes full OS, takes GBs of space, slower to start
• Container: Shares host OS kernel, MBs in size, starts in seconds

Docker Components:

• Image: Read-only template with application code and dependencies
• Container: Running instance of an image
• Dockerfile: Instructions to build an image
• Docker Hub/Registry: Repository for storing images

Example Dockerfile for .NET Core API:

# Multi-stage build for optimization
FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
WORKDIR /src

# Copy csproj and restore dependencies
COPY ["MyApi/MyApi.csproj", "MyApi/"]
RUN dotnet restore "MyApi/MyApi.csproj"

# Copy everything else and build
COPY . .
WORKDIR "/src/MyApi"
RUN dotnet build "MyApi.csproj" -c Release -o /app/build

# Publish the application
FROM build AS publish
RUN dotnet publish "MyApi.csproj" -c Release -o /app/publish /p:UseAppHost=false

# Build runtime image
FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS final
WORKDIR /app
EXPOSE 80
EXPOSE 443
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "MyApi.dll"]

Docker Compose for Multi-Container Setup:

version: '3.8'

services:
  api:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "5000:80"
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
      - ConnectionStrings__DefaultConnection=Server=db;Database=MyDb;User=sa;Password=YourPassword123!
    depends_on:
      - db
    networks:
      - app-network

  db:
    image: mcr.microsoft.com/mssql/server:2022-latest
    environment:
      - ACCEPT_EULA=Y
      - SA_PASSWORD=YourPassword123!
    ports:
      - "1433:1433"
    volumes:
      - sqldata:/var/opt/mssql
    networks:
      - app-network

volumes:
  sqldata:

networks:
  app-network:
    driver: bridge

Benefits of Containerization:

1. Consistency: Same environment in dev, test, and production
2. Isolation: Applications run independently without conflicts
3. Portability: Run anywhere Docker is supported
4. Scalability: Easy to scale horizontally
5. Resource Efficiency: Lightweight compared to VMs
6. Version Control: Images are versioned and immutable

Common Docker Commands:

# Build image
docker build -t myapi:v1 .

# Run container
docker run -d -p 5000:80 --name myapi-container myapi:v1

# View running containers
docker ps

# View logs
docker logs myapi-container

# Stop container
docker stop myapi-container

# Remove container
docker rm myapi-container