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KraftCloud

Run a .NET app

In this guide we create and deploy a simple .NET-based HTTP web server. To run this example, follow these steps:

  1. Install the kraft CLI tool and a container runtime engine, e.g. Docker.

  2. Clone the examples repository and cd into the examples/http-dotnet8.0/ directory:

Terminal window
git clone https://github.com/kraftcloud/examples
cd examples/http-dotnet8.0/

Make sure to log into KraftCloud by setting your token and a metro close to you. We use fra0 (Frankfurt, 🇩🇪) in this guide:

Terminal window
# Set KraftCloud access token
export KRAFTCLOUD_TOKEN=token
# Set metro to Frankfurt, DE
export KRAFTCLOUD_METRO=fra0

When done, invoke the following command to deploy this application on KraftCloud:

Terminal window
kraft cloud deploy -p 443:8080 -M 512 .

The output shows the instance URL and other details:

Terminal window
[●] Deployed successfully!
 │
 ├────────── name: http-dotnet80-dsmkh
 ├────────── uuid: 25459494-cb43-4009-9d05-f0996de5b7e4
 ├───────── state: starting
 ├─────────── url: cold-fog-hl98aw6q.fra0.kraft.host
 ├───────── image: http-dotnet80@sha256:4fad7453995ae96b636696e9929ee0e7376bfbbd63ab9698c1f1e02602aa2575
 ├──────── memory: 512 MiB
 ├─ service group: cold-fog-hl98aw6q
 ├── private fqdn: http-dotnet80-dsmkh.internal
 ├──── private ip: 172.16.3.1
 └────────── args: /usr/bin/app/src

In this case, the instance name is http-dotnet80-dsmkh and the URL is https://cold-fog-hl98aw6q.fra0.kraft.host. They are different for each run.

Use curl to query the KraftCloud instance of the .NET-based HTTP web server:

Terminal window
curl https://cold-fog-hl98aw6q.fra0.kraft.host
Hello, World!

At any point in time, you can list information about the instance:

Terminal window
kraft cloud instance list
NAME                 FQDN                                    STATE    CREATED AT     IMAGE                                                     MEMORY   ARGS                                                      BOOT TIME
http-dotnet80-dsmkh  cold-fog-hl98aw6q.fra0.kraft.host       running  2 minutes ago  razvan.unikraft.io/http-dotnet80@sha256:4fad7453995ae...  512 MiB  /usr/bin/app/src                                          328.69 ms

When done, you can remove the instance:

Terminal window
kraft cloud instance remove http-dotnet80-dsmkh

Customize your Application

To customize the application, update the files in the repository, listed below:

  • SimpleHttpServer.cs: the actual .NET HTTP server
  • Kraftfile: the KraftCloud specification
  • Dockerfile: the Docker-specified application filesystem
// https://codingvision.net/c-simple-http-server


using System;
using System.Net;
using System.IO;
using System.Text;


namespace test
{
    class SimpleHttpServer
    {
            static void Main(string[] args)
            {
                    HttpListener server = new HttpListener();
                    server.Prefixes.Add("http://*:8080/");


                    server.Start();
                    Console.WriteLine("Listening on port 8080 ...");


                    while (true)
                    {
                            HttpListenerContext context = server.GetContext();
                            HttpListenerResponse response = context.Response;


                            byte[] buffer = Encoding.UTF8.GetBytes("Hello, World!\n");
                            response.ContentLength64 = buffer.Length;
                            response.OutputStream.Write(buffer, 0, buffer.Length);


                            context.Response.Close();
                    }


            }
    }
}

Lines in the Kraftfile have the following roles:

  • spec: v0.6: The current Kraftfile specification version is 0.6.

  • runtime: base-compat:latest: The runtime kernel to use is the base compatibility kernel.

  • rootfs: ./Dockerfile: Build the application root filesystem using the Dockerfile.

  • cmd:: Use as the starting command of the instance.

Lines in the Dockerfile have the following roles:

  • WORKDIR /src: Use the /src directory as the working directory.

  • RUN dotnet new console: Create a new dotnet project.

  • RUN rm Program.cs: Remove template source code file.

  • COPY ./SimpleHttpServer.cs .: Copy the source code of the HTTP server.

  • RUN dotnet build .: Build dotnet project.

  • FROM scratch: Build the filesystem from the scratch container image, to create a base image.

  • COPY --from=build ...: Copy on the required files from the filesystem: the binary executable, the .NET framework files and the binary library files.

The following options are available for customizing the application:

  • If only updating the implementation in the SimpleHttpServer.rs source file, no other change is required.

  • If new files are added, these have to be copied in the application filesystem, using the COPY command in the Dockerfile.

  • More extensive changes may require expanding the Dockerfile with additional Dockerfile commands.

Learn More

Use the --help option for detailed information on using KraftCloud:

Terminal window
kraft cloud --help

Or visit the CLI Reference.