Csharp Runner

.NET 10 Docker-Host Docker-Worker License

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C# Runner is a high-performance and secure platform for executing C# code online. It's built on a Host-Worker architecture that isolates code execution in Docker containers and supports dual protocols: HTTP and MCP (Model Context Protocol).

✨ Core Features

• 🔒 Secure & Reliable

  • Container Isolation: Untrusted code runs in isolated Docker Worker containers, ensuring host safety.
  • Resource Limits: Supports CPU, memory, and execution timeout limits to prevent resource abuse.
  • Network Isolation: Worker containers have restricted network access.
  • Worker Recycling: Automatically recycles a Worker instance after a configured number of runs to maintain a clean environment.

• ⚡ High-Performance

  • Worker Warm-up: Pre-compiles code on startup to ensure optimal performance from the very first run.
  • Load Balancing: Distributes tasks among multiple Workers using a Round-Robin algorithm.
  • Connection Pooling: Reuses HttpClient instances to reduce network overhead.

• 🌐 Rich Functionality

  • Dual Protocol Support: Offers both an HTTP REST API and an MCP interface.
  • Streaming Output: Streams code output, results, and errors in real-time using Server-Sent Events (SSE).
  • User-friendly Web UI: Features a clean code editor with syntax highlighting and Ctrl+Enter shortcut for execution.
  • Out-of-the-Box: Provides a complete Docker Compose solution for one-click deployment.

🚀 Quick Start

Prerequisites:

• Docker and Docker Compose

One-Click Deploy with Docker Compose:

# Download the docker-compose.yml file
curl -L https://raw.githubusercontent.com/sdcb/csharp-runner/refs/heads/master/docker-compose.yml -o docker-compose.yml

# Start the services in detached mode
docker compose up -d

For Windows:

# Download the docker-compose.yml file
Invoke-WebRequest -Uri "https://raw.githubusercontent.com/sdcb/csharp-runner/refs/heads/master/docker-compose.yml" -OutFile "docker-compose.yml"

# Start the services in detached mode
docker compose -p csharp-runner up -d

Once deployed, open your browser to http://localhost:5050 to access the web UI.

🔧 Configuration

Docker Compose

The docker-compose.yml file defines the Host and Worker services. You can scale the number of Workers by changing deploy.replicas and configure Worker behavior via environment variables.

services:
  host:
    image: sdcb/csharp-runner-host:latest
    container_name: csharp-runner-host
    ports:
      - "5050:8080"
    restart: unless-stopped

  worker:
    image: sdcb/csharp-runner-worker:latest
    environment:
      - MaxRuns=2           # Max runs per worker (0=unlimited)
      - Register=true       # Auto-register to the Host
      - RegisterHostUrl=http://host:8080
      - WarmUp=false        # Enable warm-up (recommended for standalone deployment)
    restart: unless-stopped
    depends_on:
      - host
    deploy:
      replicas: 3
      resources:
        limits:
          cpus: 0.50
          memory: 256M
          pids: 32
        reservations:
          cpus: 0.25
          memory: 128M

Worker Environment Variables

Parameter	Description	Default
MaxRuns	The maximum number of times a Worker can execute code (0=unlimited).	0
Register	Whether to auto-register to the Host service.	false
RegisterHostUrl	The registration URL of the Host service.	http://host
ExposedUrl	The externally exposed URL of the Worker (optional).	null
WarmUp	Whether to perform a warm-up on startup.	false
MaxTimeout	Maximum execution timeout in milliseconds.	30000

📡 API Usage

HTTP API (SSE)

Execute code by sending a POST request to /api/run. The response is streamed as Server-Sent Events (SSE).

Request

POST /api/run
Content-Type: application/json

{
  "code": "Console.WriteLine(\"Hello, World!\"); return 42;",
  "timeout": 30000
}

Response Stream

data: {"kind":"stdout","stdOutput":"Hello, World!"}

data: {"kind":"result","result":42}

data: {"kind":"end","elapsed":150,"stdOutput":"Hello, World!","stdError":""}

MCP Protocol

The MCP endpoint is at /mcp and supports the run_code tool.

Request Example

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "run_code",
    "arguments": {
      "code": "Console.WriteLine(\"Hello from MCP!\");"
    }
  },
  "id": 1
}

🏗️ Architecture & Development Guide

System Architecture

• Host: Provides the public API and web UI. It receives requests, manages a pool of Workers, and handles load balancing.
• Worker: Runs in an isolated sandbox environment, responsible for executing the C# code and returning the result.

Project Structure

src/
├── Sdcb.CSharpRunner.Host/     # Host Service (ASP.NET Core)
├── Sdcb.CSharpRunner.Worker/   # Worker Service (Console App)
└── Sdcb.CSharpRunner.Shared/   # Shared Library (DTOs, etc.)

Local Development

1. Run the Host Service

   cd src/Sdcb.CSharpRunner.Host
   dotnet run
   

2. Run the Worker Service

   cd src/Sdcb.CSharpRunner.Worker
   dotnet run
   

Building Custom Images

# Build the Host image
dotnet publish ./src/Sdcb.CSharpRunner.Host/Sdcb.CSharpRunner.Host.csproj -c Release /t:PublishContainer /p:ContainerRepository=csharp-runner-host

# Build the Worker image
dotnet publish ./src/Sdcb.CSharpRunner.Worker/Sdcb.CSharpRunner.Worker.csproj -c Release /t:PublishContainer /p:ContainerRepository=csharp-runner-worker

🤝 Contributing

Contributions via Issues and Pull Requests are welcome! Please follow these steps:

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

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