SGLang is a fast serving framework for large language models and vision language models. It makes your interaction with models faster and more controllable by co-designing the backend runtime and frontend language.
The core features include:
- Fast Backend Runtime: Efficient serving with RadixAttention for prefix caching, jump-forward constrained decoding, continuous batching, token attention (paged attention), tensor parallelism, flashinfer kernels, and quantization (AWQ/FP8/GPTQ/Marlin).
- Flexible Frontend Language: Enables easy programming of LLM applications with chained generation calls, advanced prompting, control flow, multiple modalities, parallelism, and external interactions.
- [2024/07] 🔥 Faster Llama3 Serving with SGLang Runtime (vs. TensorRT-LLM, vLLM) (blog).
- [2024/04] SGLang is used by the official LLaVA-NeXT (video) release (blog).
- [2024/02] SGLang enables 3x faster JSON decoding with compressed finite state machine (blog).
More
- Install
- Backend: SGLang Runtime (SRT)
- Frontend: Structured Generation Language (SGLang)
- Benchmark And Performance
- Roadmap
- Citation And Acknowledgment
pip install --upgrade pip
pip install "sglang[all]"
# Install FlashInfer CUDA kernels
pip install flashinfer -i https://flashinfer.ai/whl/cu121/torch2.4/
# Use the last release branch
git clone -b v0.2.13 https://github.com/sgl-project/sglang.git
cd sglang
pip install --upgrade pip
pip install -e "python[all]"
# Install FlashInfer CUDA kernels
pip install flashinfer -i https://flashinfer.ai/whl/cu121/torch2.4/
The docker images are available on Docker Hub as lmsysorg/sglang, built from Dockerfile.
Replace <secret> below with your huggingface hub token.
docker run --gpus all \
-p 30000:30000 \
-v ~/.cache/huggingface:/root/.cache/huggingface \
--env "HF_TOKEN=<secret>" \
--ipc=host \
lmsysorg/sglang:latest \
python3 -m sglang.launch_server --model-path meta-llama/Meta-Llama-3.1-8B-Instruct --host 0.0.0.0 --port 30000
> This method is recommended if you plan to serve it as a service.
> A better approach is to use the [k8s-sglang-service.yaml](./docker/k8s-sglang-service.yaml).
- Copy the compose.yml to your local machine
- Execute the command
docker compose up -din your terminal.
To deploy on Kubernetes or 12+ clouds, you can use [SkyPilot](https://github.com/skypilot-org/skypilot).
SkyPilot YAML:
- Install SkyPilot and set up Kubernetes cluster or cloud access: see SkyPilot's documentation.
- Deploy on your own infra with a single command and get the HTTP API endpoint:
SkyPilot YAML: sglang.yaml
# sglang.yaml
envs:
HF_TOKEN: null
resources:
image_id: docker:lmsysorg/sglang:latest
accelerators: A100
ports: 30000
run: |
conda deactivate
python3 -m sglang.launch_server \
--model-path meta-llama/Meta-Llama-3.1-8B-Instruct \
--host 0.0.0.0 \
--port 30000# Deploy on any cloud or Kubernetes cluster. Use --cloud <cloud> to select a specific cloud provider.
HF_TOKEN=<secret> sky launch -c sglang --env HF_TOKEN sglang.yaml
# Get the HTTP API endpoint
sky status --endpoint 30000 sglang- To further scale up your deployment with autoscaling and failure recovery, check out the SkyServe + SGLang guide.
- FlashInfer is currently one of the dependencies that must be installed for SGLang. If you are using NVIDIA GPU devices below sm80, such as T4, you can't use SGLang for the time being. We expect to resolve this issue soon, so please stay tuned. If you encounter any FlashInfer-related issues on sm80+ devices (e.g., A100, L40S, H100), consider using Triton's kernel by
--disable-flashinfer --disable-flashinfer-samplingand raise a issue. - If you only need to use the OpenAI backend, you can avoid installing other dependencies by using
pip install "sglang[openai]".
The SGLang Runtime (SRT) is an efficient serving engine.
Launch a server
python -m sglang.launch_server --model-path meta-llama/Meta-Llama-3-8B-Instruct --port 30000
Send a request
curl http://localhost:30000/generate \
-H "Content-Type: application/json" \
-d '{
"text": "Once upon a time,",
"sampling_params": {
"max_new_tokens": 16,
"temperature": 0
}
}'
Learn more about the argument format here.
In addition, the server supports OpenAI-compatible APIs.
import openai
client = openai.Client(
base_url="http://127.0.0.1:30000/v1", api_key="EMPTY")
# Text completion
response = client.completions.create(
model="default",
prompt="The capital of France is",
temperature=0,
max_tokens=32,
)
print(response)
# Chat completion
response = client.chat.completions.create(
model="default",
messages=[
{"role": "system", "content": "You are a helpful AI assistant"},
{"role": "user", "content": "List 3 countries and their capitals."},
],
temperature=0,
max_tokens=64,
)
print(response)It supports streaming, vision, and most features of the Chat/Completions/Models/Batch endpoints specified by the OpenAI API Reference.
- Add
--tp 2to enable multi-GPU tensor parallelism. If it reports the error "peer access is not supported between these two devices", add--enable-p2p-checkto the server launch command.
python -m sglang.launch_server --model-path meta-llama/Meta-Llama-3-8B-Instruct --port 30000 --tp 2
- Add
--dp 2to enable multi-GPU data parallelism. It can also be used together with tensor parallelism. Data parallelism is better for throughput if there is enough memory.
python -m sglang.launch_server --model-path meta-llama/Meta-Llama-3-8B-Instruct --port 30000 --dp 2 --tp 2
- If you see out-of-memory errors during serving, try to reduce the memory usage of the KV cache pool by setting a smaller value of
--mem-fraction-static. The default value is0.9.
python -m sglang.launch_server --model-path meta-llama/Meta-Llama-3-8B-Instruct --port 30000 --mem-fraction-static 0.7
- See hyperparameter_tuning.md on tuning hyperparameters for better performance.
- If you see out-of-memory errors during prefill for long prompts, try to set a smaller chunked prefill size.
python -m sglang.launch_server --model-path meta-llama/Meta-Llama-3-8B-Instruct --port 30000 --chunked-prefill-size 4096
- Add
--nnodes 2to run tensor parallelism on multiple nodes. If you have two nodes with two GPUs on each node and want to run TP=4, letsgl-dev-0be the hostname of the first node and50000be an available port.
# Node 0
python -m sglang.launch_server --model-path meta-llama/Meta-Llama-3-8B-Instruct --tp 4 --nccl-init sgl-dev-0:50000 --nnodes 2 --node-rank 0
# Node 1
python -m sglang.launch_server --model-path meta-llama/Meta-Llama-3-8B-Instruct --tp 4 --nccl-init sgl-dev-0:50000 --nnodes 2 --node-rank 1
- If the model does not have a template in the Hugging Face tokenizer, you can specify a custom chat template.
- To enable experimental torch.compile support, you can add
--enable-torch-compile. It accelerates small models on small batch sizes. - To enable fp8 quantization, you can add
--quantization fp8on a fp16 checkpoint or directly load a fp8 checkpoint without specifying any arguments.
- Llama / Llama 2 / Llama 3 / Llama 3.1
- Mistral / Mixtral / Mistral NeMo
- Gemma / Gemma 2
- Qwen / Qwen 2 / Qwen 2 MoE
- DeepSeek / DeepSeek 2
- LLaVA 1.5 / 1.6
python -m sglang.launch_server --model-path liuhaotian/llava-v1.5-7b --tokenizer-path llava-hf/llava-1.5-7b-hf --chat-template vicuna_v1.1 --port 30000python -m sglang.launch_server --model-path liuhaotian/llava-v1.6-vicuna-7b --tokenizer-path llava-hf/llava-1.5-7b-hf --chat-template vicuna_v1.1 --port 30000python -m sglang.launch_server --model-path liuhaotian/llava-v1.6-34b --tokenizer-path liuhaotian/llava-v1.6-34b-tokenizer --port 30000
- LLaVA-NeXT-Video
- Yi-VL
- see srt_example_yi_vl.py.
- StableLM
- Command-R
- DBRX
- Grok
- ChatGLM
- InternLM 2
Instructions for supporting a new model are here.
To use model from ModelScope, setting environment variable SGLANG_USE_MODELSCOPE.
export SGLANG_USE_MODELSCOPE=true
Launch Qwen2-7B-Instruct Server
SGLANG_USE_MODELSCOPE=true python -m sglang.launch_server --model-path qwen/Qwen2-7B-Instruct --port 30000
## Run 405B (fp8) on a single node
python -m sglang.launch_server --model-path meta-llama/Meta-Llama-3.1-405B-Instruct-FP8 --tp 8
## Run 405B (fp16) on two nodes
# replace the `172.16.4.52:20000` with your own first node ip address and port, disable CUDA Graph temporarily
# on the first node
GLOO_SOCKET_IFNAME=eth0 python3 -m sglang.launch_server --model-path meta-llama/Meta-Llama-3.1-405B-Instruct --tp 16 --nccl-init-addr 172.16.4.52:20000 --nnodes 2 --node-rank 0 --disable-cuda-graph --mem-frac 0.75
# on the second
GLOO_SOCKET_IFNAME=eth0 python3 -m sglang.launch_server --model-path meta-llama/Meta-Llama-3.1-405B-Instruct --tp 16 --nccl-init-addr 172.16.4.52:20000 --nnodes 2 --node-rank 1 --disable-cuda-graph --mem-frac 0.75- Benchmark a single static batch by running the following command without launching a server. The arguments are the same as for
launch_server.py. Note that this is not a dynamic batching server, so it may run out of memory for a batch size that a real server can handle. A real server truncates the prefill into several batches, while this unit test does not. For accurate large batch testing, consider usingsglang.bench_serving.python -m sglang.bench_latency --model-path meta-llama/Meta-Llama-3-8B-Instruct --batch 32 --input-len 256 --output-len 32 - Benchmark online serving. Launch a server first and run the following command.
python3 -m sglang.bench_serving --backend sglang --num-prompt 10
The frontend language can be used with local models or API models. It is an alternative to the OpenAI API. You may found it easier to use for complex prompting workflow.
The example below shows how to use sglang to answer a mulit-turn question.
First, launch a server with
python -m sglang.launch_server --model-path meta-llama/Meta-Llama-3-8B-Instruct --port 30000
Then, connect to the server and answer a multi-turn question.
from sglang import function, system, user, assistant, gen, set_default_backend, RuntimeEndpoint
@function
def multi_turn_question(s, question_1, question_2):
s += system("You are a helpful assistant.")
s += user(question_1)
s += assistant(gen("answer_1", max_tokens=256))
s += user(question_2)
s += assistant(gen("answer_2", max_tokens=256))
set_default_backend(RuntimeEndpoint("http://localhost:30000"))
state = multi_turn_question.run(
question_1="What is the capital of the United States?",
question_2="List two local attractions.",
)
for m in state.messages():
print(m["role"], ":", m["content"])
print(state["answer_1"])Set the OpenAI API Key
export OPENAI_API_KEY=sk-******
Then, answer a multi-turn question.
from sglang import function, system, user, assistant, gen, set_default_backend, OpenAI
@function
def multi_turn_question(s, question_1, question_2):
s += system("You are a helpful assistant.")
s += user(question_1)
s += assistant(gen("answer_1", max_tokens=256))
s += user(question_2)
s += assistant(gen("answer_2", max_tokens=256))
set_default_backend(OpenAI("gpt-3.5-turbo"))
state = multi_turn_question.run(
question_1="What is the capital of the United States?",
question_2="List two local attractions.",
)
for m in state.messages():
print(m["role"], ":", m["content"])
print(state["answer_1"])Anthropic and VertexAI (Gemini) models are also supported. You can find more examples at examples/quick_start.
To begin with, import sglang.
import sglang as sglsglang provides some simple primitives such as gen, select, fork, image.
You can implement your prompt flow in a function decorated by sgl.function.
You can then invoke the function with run or run_batch.
The system will manage the state, chat template, parallelism and batching for you.
The complete code for the examples below can be found at readme_examples.py
You can use any Python code within the function body, including control flow, nested function calls, and external libraries.
@sgl.function
def tool_use(s, question):
s += "To answer this question: " + question + ". "
s += "I need to use a " + sgl.gen("tool", choices=["calculator", "search engine"]) + ". "
if s["tool"] == "calculator":
s += "The math expression is" + sgl.gen("expression")
elif s["tool"] == "search engine":
s += "The key word to search is" + sgl.gen("word")Use fork to launch parallel prompts.
Because sgl.gen is non-blocking, the for loop below issues two generation calls in parallel.
@sgl.function
def tip_suggestion(s):
s += (
"Here are two tips for staying healthy: "
"1. Balanced Diet. 2. Regular Exercise.\n\n"
)
forks = s.fork(2)
for i, f in enumerate(forks):
f += f"Now, expand tip {i+1} into a paragraph:\n"
f += sgl.gen(f"detailed_tip", max_tokens=256, stop="\n\n")
s += "Tip 1:" + forks[0]["detailed_tip"] + "\n"
s += "Tip 2:" + forks[1]["detailed_tip"] + "\n"
s += "In summary" + sgl.gen("summary")Use sgl.image to pass an image as input.
@sgl.function
def image_qa(s, image_file, question):
s += sgl.user(sgl.image(image_file) + question)
s += sgl.assistant(sgl.gen("answer", max_tokens=256)See also srt_example_llava.py.
Use regex to specify a regular expression as a decoding constraint.
This is only supported for local models.
@sgl.function
def regular_expression_gen(s):
s += "Q: What is the IP address of the Google DNS servers?\n"
s += "A: " + sgl.gen(
"answer",
temperature=0,
regex=r"((25[0-5]|2[0-4]\d|[01]?\d\d?).){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)",
)Use regex to specify a JSON schema with a regular expression.
character_regex = (
r"""\{\n"""
+ r""" "name": "[\w\d\s]{1,16}",\n"""
+ r""" "house": "(Gryffindor|Slytherin|Ravenclaw|Hufflepuff)",\n"""
+ r""" "blood status": "(Pure-blood|Half-blood|Muggle-born)",\n"""
+ r""" "occupation": "(student|teacher|auror|ministry of magic|death eater|order of the phoenix)",\n"""
+ r""" "wand": \{\n"""
+ r""" "wood": "[\w\d\s]{1,16}",\n"""
+ r""" "core": "[\w\d\s]{1,16}",\n"""
+ r""" "length": [0-9]{1,2}\.[0-9]{0,2}\n"""
+ r""" \},\n"""
+ r""" "alive": "(Alive|Deceased)",\n"""
+ r""" "patronus": "[\w\d\s]{1,16}",\n"""
+ r""" "bogart": "[\w\d\s]{1,16}"\n"""
+ r"""\}"""
)
@sgl.function
def character_gen(s, name):
s += name + " is a character in Harry Potter. Please fill in the following information about this character.\n"
s += sgl.gen("json_output", max_tokens=256, regex=character_regex)See also json_decode.py for an additional example on specifying formats with Pydantic models.
Use run_batch to run a batch of requests with continuous batching.
@sgl.function
def text_qa(s, question):
s += "Q: " + question + "\n"
s += "A:" + sgl.gen("answer", stop="\n")
states = text_qa.run_batch(
[
{"question": "What is the capital of the United Kingdom?"},
{"question": "What is the capital of France?"},
{"question": "What is the capital of Japan?"},
],
progress_bar=True
)Add stream=True to enable streaming.
@sgl.function
def text_qa(s, question):
s += "Q: " + question + "\n"
s += "A:" + sgl.gen("answer", stop="\n")
state = text_qa.run(
question="What is the capital of France?",
temperature=0.1,
stream=True
)
for out in state.text_iter():
print(out, end="", flush=True)Use sgl.system， sgl.user and sgl.assistant to set roles when using Chat models. You can also define more complex role prompts using begin and end tokens.
@sgl.function
def chat_example(s):
s += sgl.system("You are a helpful assistant.")
# Same as: s += s.system("You are a helpful assistant.")
with s.user():
s += "Question: What is the capital of France?"
s += sgl.assistant_begin()
s += "Answer: " + sgl.gen(max_tokens=100, stop="\n")
s += sgl.assistant_end()- The
choicesargument insgl.genis implemented by computing the token-length normalized log probabilities of all choices and selecting the one with the highest probability. - The
regexargument insgl.genis implemented through autoregressive decoding with logit bias masking, according to the constraints set by the regex. It is compatible withtemperature=0andtemperature != 0.
Learn more at this blog.
Please cite our paper, SGLang: Efficient Execution of Structured Language Model Programs, if you find the project useful. We also learned from the design and reused code from the following projects: Guidance, vLLM, LightLLM, FlashInfer, Outlines, and LMQL.