Deploying a .NET Application to DigitalOcean Using Docker Containers and Container Registry

Deploying a .NET application to a cloud environment like DigitalOcean is a powerful way to ensure scalability, reliability, and ease of management. In this post, we’ll walk through deploying a real-world .NET application—a simple ASP.NET Core MVC app—to DigitalOcean using Docker containers and its container registry.

---

Prerequisites

Before we begin, ensure you have the following:

1. DigitalOcean Account: Sign up at DigitalOcean.

2. Docker Installed: Ensure Docker is installed and running on your local machine. Download it here.

3. dotnet CLI: Install the .NET SDK from dotnet.microsoft.com.

4. DigitalOcean CLI (doctl): Install doctl for managing DigitalOcean resources from your terminal. Follow the installation guide.

5. A Sample .NET Project: Clone the sample app:

    git clone https://github.com/dotnet-architecture/eShopOnWeb.git
    cd eShopOnWeb
   

---

Step 1: Build and Containerize the .NET Application

1.1 Create a Dockerfile

Navigate to the root directory of the sample app and create a Dockerfile:

# Use the official ASP.NET runtime image
FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
WORKDIR /app
EXPOSE 5000

# Use the .NET SDK image for building the app
FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
WORKDIR /src
COPY ["src/Web/Web.csproj", "src/Web/"]
RUN dotnet restore "src/Web/Web.csproj"
COPY . .
WORKDIR "/src/src/Web"
RUN dotnet build "Web.csproj" -c Release -o /app/build

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

# Create the final runtime image
FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "Web.dll"]

1.2 Build the Docker Image

Build the Docker image for your app:

docker build -t eshoponweb:latest .

1.3 Test Locally

Run the container locally to ensure it works:

docker run -p 5000:5000 eshoponweb:latest

Visit http://localhost:5000 in your browser to verify the app is running.

---

Step 2: Push the Image to DigitalOcean Container Registry

2.1 Authenticate with DigitalOcean

Log in to your DigitalOcean account using the doctl CLI:

doctl auth init

2.2 Create a Container Registry

Create a new container registry in DigitalOcean:

doctl registry create my-registry

Retrieve the registry URL:

doctl registry get

Example output:

Name:              my-registry
Endpoint:          registry.digitalocean.com/my-registry

2.3 Tag and Push the Docker Image

Tag your image for the DigitalOcean registry:

docker tag eshoponweb:latest registry.digitalocean.com/my-registry/eshoponweb:latest

Push the image:

docker push registry.digitalocean.com/my-registry/eshoponweb:latest

Verify the image was pushed successfully:

doctl registry repository list my-registry

---

Step 3: Deploy the App to a DigitalOcean Droplet

3.1 Create a Droplet

Spin up a new DigitalOcean droplet using the Docker image:

doctl compute droplet create \
  my-droplet \
  --region nyc3 \
  --image docker-20-04 \
  --size s-1vcpu-1gb \
  --ssh-keys <your-ssh-key-id>

Retrieve the droplet’s IP address:

doctl compute droplet list

3.2 SSH Into the Droplet

SSH into the newly created droplet:

ssh root@<droplet-ip>

3.3 Pull and Run the Docker Container

1. Log in to the DigitalOcean registry from your droplet:

    docker login registry.digitalocean.com
   

   Enter your DigitalOcean personal access token when prompted.

2. Pull the container image:

    docker pull registry.digitalocean.com/my-registry/eshoponweb:latest
   

3. Run the container:

    docker run -d -p 80:5000 registry.digitalocean.com/my-registry/eshoponweb:latest
   

The app will now be accessible at http://<droplet-ip>.

---

Step 4: Automate Deployment with Docker Compose (Optional)

To manage your app and any dependencies, use a docker-compose.yml file:

version: '3.8'

services:
  eshoponweb:
    image: registry.digitalocean.com/my-registry/eshoponweb:latest
    ports:
      - "80:5000"
    environment:
      - DOTNET_ENVIRONMENT=Production

Deploy with Docker Compose:

docker-compose up -d

---

Conclusion

In this tutorial, we containerized a .NET app, pushed it to DigitalOcean’s container registry, and deployed it on a droplet. This setup ensures your app is production-ready and easily scalable. For advanced setups, consider adding CI/CD pipelines and monitoring tools.

Happy deploying!