dgx-spark-playbooks/nvidia/sglang

SGLang Inference Server

Install and use SGLang on DGX Spark

Table of Contents

• Overview
  • Time & risk
• Instructions

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Overview

Basic Idea

SGLang is a fast serving framework for large language models and vision language models that makes your interaction with models faster and more controllable by co-designing the backend runtime and frontend language. This setup uses the optimized NVIDIA SGLang NGC Container on a single NVIDIA Spark device with Blackwell architecture, providing GPU-accelerated inference with all dependencies pre-installed.

What you'll accomplish

You'll deploy SGLang in both server and offline inference modes on your NVIDIA Spark device, enabling high-performance LLM serving with support for text generation, chat completion, and vision-language tasks using models like DeepSeek-V2-Lite.

What to know before starting

• Working in a terminal environment on Linux systems
• Basic understanding of Docker containers and container management
• Familiarity with NVIDIA GPU drivers and CUDA toolkit concepts
• Experience with HTTP API endpoints and JSON request/response handling

Prerequisites

• NVIDIA Spark device with Blackwell architecture
• Docker Engine installed and running: docker --version
• NVIDIA GPU drivers installed: nvidia-smi
• NVIDIA Container Toolkit configured: docker run --rm --gpus all nvidia/cuda:12.9-base nvidia-smi
• Sufficient disk space (>20GB available): df -h
• Network connectivity for pulling NGC containers: ping nvcr.io

Ancillary files

• An offline inference python script found here on GitHub

Time & risk

Duration: 15-30 minutes for initial setup and validation

Risk level: Low - Uses pre-built, validated NGC container with minimal configuration

Rollback: Stop and remove containers with docker stop and docker rm commands

Instructions

Step 1. Verify system prerequisites

Check that your NVIDIA Spark device meets all requirements before proceeding. This step runs on your host system and ensures Docker, GPU drivers, and container toolkit are properly configured.

## Verify Docker installation
docker --version

## Check NVIDIA GPU drivers
nvidia-smi

## Test NVIDIA Container Toolkit
docker run --rm --gpus all nvidia/cuda:12.9-base-ubuntu20.04 nvidia-smi

## Check available disk space
df -h /

Step 2. Pull the SGLang NGC Container

Download the latest SGLang container from NVIDIA NGC. This step runs on the host and may take several minutes depending on your network connection.

TODO: Verify the exact container tag/version for SGLang NGC container

## Pull the SGLang container
docker pull nvcr.io/nvidia/sglang:<VERSION>-py3

## Verify the image was downloaded
docker images | grep sglang

Step 3. Launch SGLang container for server mode

Start the SGLang container in server mode to enable HTTP API access. This runs the inference server inside the container, exposing it on port 30000 for client connections.

## Launch container with GPU support and port mapping
docker run --gpus all -it --rm \
    -p 30000:30000 \
    -v /tmp:/tmp \
    nvcr.io/nvidia/sglang:<VERSION>-py3 \
    bash

Step 4. Start the SGLang inference server

Inside the container, launch the HTTP inference server with a supported model. This step runs inside the Docker container and starts the SGLang server daemon.

## Start the inference server with DeepSeek-V2-Lite model
python3 -m sglang.launch_server \
    --model-path deepseek-ai/DeepSeek-V2-Lite \
    --host 0.0.0.0 \
    --port 30000 \
    --trust-remote-code \
    --tp 1 &

## Wait for server to initialize
sleep 30

## Check server status
curl http://localhost:30000/health

Step 5. Test client-server inference

From a new terminal on your host system, test the SGLang server API to ensure it's working correctly. This validates that the server is accepting requests and generating responses.

## Test with curl
curl -X POST http://localhost:30000/generate \
    -H "Content-Type: application/json" \
    -d '{
        "text": "What does NVIDIA love?",
        "sampling_params": {
            "temperature": 0.7,
            "max_new_tokens": 100
        }
    }'

Step 6. Test Python client API

Create a simple Python script to test programmatic access to the SGLang server. This runs on the host system and demonstrates how to integrate SGLang into applications.

import requests

## Send prompt to server
response = requests.post('http://localhost:30000/generate', json={
    'text': 'What does NVIDIA love?',
    'sampling_params': {
        'temperature': 0.7,
        'max_new_tokens': 100,
    },
})

print(f"Response: {response.json()['text']}")

Step 7. Test offline inference mode

Launch a new container instance for offline inference to demonstrate local model usage without HTTP server. This runs entirely within the container for batch processing scenarios.

TO DO: NEEDS TO HAVE SCRIPT FROM ASSETS PROPERLY INCORPORATED. See here

Step 8. Validate installation

Confirm that both server and offline modes are working correctly. This step verifies the complete SGLang setup and ensures reliable operation.

## Check server mode (from host)
curl http://localhost:30000/health
curl -X POST http://localhost:30000/generate -H "Content-Type: application/json" \
    -d '{"text": "Hello", "sampling_params": {"max_new_tokens": 10}}'

## Check container logs
docker ps
docker logs <CONTAINER_ID>

Step 9. Troubleshooting

Common issues and their resolutions:

Symptom	Cause	Fix
Container fails to start with GPU errors	NVIDIA drivers/toolkit missing	Install nvidia-container-toolkit, restart Docker
Server responds with 404 or connection refused	Server not fully initialized	Wait 60 seconds, check container logs
Out of memory errors during model loading	Insufficient GPU memory	Use smaller model or increase --tp parameter
Model download fails	Network connectivity issues	Check internet connection, retry download
Permission denied accessing /tmp	Volume mount issues	Use full path: -v /tmp:/tmp or create dedicated directory

Step 10. Cleanup and rollback

Stop and remove containers to clean up resources. This step returns your system to its original state.

Warning

This will stop all SGLang containers and remove temporary data.

## Stop all SGLang containers
docker ps | grep sglang | awk '{print $1}' | xargs docker stop

## Remove stopped containers
docker container prune -f

## Remove SGLang images (optional)
docker rmi nvcr.io/nvidia/sglang:<VERSION>-py3

Step 11. Next steps

With SGLang successfully deployed, you can now:

• Integrate the HTTP API into your applications using the /generate endpoint
• Experiment with different models by changing the --model-path parameter
• Scale up using multiple GPUs by adjusting the --tp (tensor parallel) setting
• Deploy production workloads using the container orchestration platform of your choice