Support v1/chat/completions (#50)

README.md

@@ -248,6 +248,8 @@ In addition, the server supports an experimental OpenAI-compatible API.
 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",
@@ -255,6 +257,46 @@ response = client.completions.create(
 	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)
+```
+
+In above example, the server uses the chat template specified in the model tokenizer.
+You can override the chat template if needed when launching the server:
+
+```
+python -m sglang.launch_server --model-path meta-llama/Llama-2-7b-chat-hf --port 30000
+--chat-template llama-2
+```
+
+If the chat template you are looking for is missing, you are welcome to contribute it.
+Meanwhile, you can also temporary register your chat template as follows:
+
+```json
+{
+  "name": "my_model",
+  "system": "<|im_start|>system",
+  "user": "<|im_start|>user",
+  "assistant": "<|im_start|>assistant",
+  "sep_style": "CHATML",
+  "sep": "<|im_end|>",
+  "stop_str": ["<|im_end|>", "<|im_start|>"]
+}
+```
+
+```
+python -m sglang.launch_server --model-path meta-llama/Llama-2-7b-chat-hf --port 30000
+--chat-template ./my_model_template.json
 ```
 
 ### Additional Arguments

python/sglang/srt/conversation.py

+# Adapted from
+# https://github.com/lm-sys/FastChat/blob/main/fastchat/conversation.py
+from sglang.srt.managers.openai_protocol import ChatCompletionRequest
+from enum import IntEnum, auto
+import dataclasses
+from typing import Dict, List, Tuple, Union
+
+
+class SeparatorStyle(IntEnum):
+    """Separator styles."""
+
+    ADD_COLON_SINGLE = auto()
+    ADD_COLON_TWO = auto()
+    ADD_COLON_SPACE_SINGLE = auto()
+    NO_COLON_SINGLE = auto()
+    NO_COLON_TWO = auto()
+    ADD_NEW_LINE_SINGLE = auto()
+    LLAMA2 = auto()
+    CHATGLM = auto()
+    CHATML = auto()
+    CHATINTERN = auto()
+    DOLLY = auto()
+    RWKV = auto()
+    PHOENIX = auto()
+    ROBIN = auto()
+    FALCON_CHAT = auto()
+    CHATGLM3 = auto()
+    DEEPSEEK_CHAT = auto()
+    METAMATH = auto()
+
+
+@dataclasses.dataclass
+class Conversation:
+    """A class that manages prompt templates and keeps all conversation history."""
+
+    # The name of this template
+    name: str
+    # The template of the system prompt
+    system_template: str = "{system_message}"
+    # The system message
+    system_message: str = ""
+    # The names of two roles
+    roles: Tuple[str] = ("USER", "ASSISTANT")
+    # All messages. Each item is (role, message).
+    messages: List[List[str]] = ()
+    # The number of few shot examples
+    offset: int = 0
+    # The separator style and configurations
+    sep_style: SeparatorStyle = SeparatorStyle.ADD_COLON_SINGLE
+    sep: str = "\n"
+    sep2: str = None
+    # Stop criteria (the default one is EOS token)
+    stop_str: Union[str, List[str]] = None
+
+    def get_prompt(self) -> str:
+        """Get the prompt for generation."""
+        system_prompt = self.system_template.format(system_message=self.system_message)
+        if self.sep_style == SeparatorStyle.ADD_COLON_SINGLE:
+            ret = system_prompt + self.sep
+            for role, message in self.messages:
+                if message:
+                    ret += role + ": " + message + self.sep
+                else:
+                    ret += role + ":"
+            return ret
+        elif self.sep_style == SeparatorStyle.ADD_COLON_TWO:
+            seps = [self.sep, self.sep2]
+            ret = system_prompt + seps[0]
+            for i, (role, message) in enumerate(self.messages):
+                if message:
+                    ret += role + ": " + message + seps[i % 2]
+                else:
+                    ret += role + ":"
+            return ret
+        elif self.sep_style == SeparatorStyle.ADD_COLON_SPACE_SINGLE:
+            ret = system_prompt + self.sep
+            for role, message in self.messages:
+                if message:
+                    ret += role + ": " + message + self.sep
+                else:
+                    ret += role + ": "  # must be end with a space
+            return ret
+        elif self.sep_style == SeparatorStyle.ADD_NEW_LINE_SINGLE:
+            ret = "" if system_prompt == "" else system_prompt + self.sep
+            for role, message in self.messages:
+                if message:
+                    ret += role + "\n" + message + self.sep
+                else:
+                    ret += role + "\n"
+            return ret
+        elif self.sep_style == SeparatorStyle.NO_COLON_SINGLE:
+            ret = system_prompt
+            for role, message in self.messages:
+                if message:
+                    ret += role + message + self.sep
+                else:
+                    ret += role
+            return ret
+        elif self.sep_style == SeparatorStyle.NO_COLON_TWO:
+            seps = [self.sep, self.sep2]
+            ret = system_prompt
+            for i, (role, message) in enumerate(self.messages):
+                if message:
+                    ret += role + message + seps[i % 2]
+                else:
+                    ret += role
+            return ret
+        elif self.sep_style == SeparatorStyle.RWKV:
+            ret = system_prompt
+            for i, (role, message) in enumerate(self.messages):
+                if message:
+                    ret += role + ": " + message.replace("\r\n", "\n").replace("\n\n", "\n")
+                    ret += "\n\n"
+                else:
+                    ret += role + ":"
+            return ret
+        elif self.sep_style == SeparatorStyle.LLAMA2:
+            seps = [self.sep, self.sep2]
+            if self.system_message:
+                ret = system_prompt
+            else:
+                ret = "[INST] "
+            for i, (role, message) in enumerate(self.messages):
+                tag = self.roles[i % 2]
+                if message:
+                    if i == 0:
+                        ret += message + " "
+                    else:
+                        ret += tag + " " + message + seps[i % 2]
+                else:
+                    ret += tag
+            return ret
+        elif self.sep_style == SeparatorStyle.CHATGLM:
+            # source: https://huggingface.co/THUDM/chatglm-6b/blob/1d240ba371910e9282298d4592532d7f0f3e9f3e/modeling_chatglm.py#L1302-L1308
+            # source2: https://huggingface.co/THUDM/chatglm2-6b/blob/e186c891cf64310ac66ef10a87e6635fa6c2a579/modeling_chatglm.py#L926
+            round_add_n = 1 if self.name == "chatglm2" else 0
+            if system_prompt:
+                ret = system_prompt + self.sep
+            else:
+                ret = ""
+
+            for i, (role, message) in enumerate(self.messages):
+                if i % 2 == 0:
+                    ret += f"[Round {i//2 + round_add_n}]{self.sep}"
+
+                if message:
+                    ret += f"{role}：{message}{self.sep}"
+                else:
+                    ret += f"{role}："
+            return ret
+        elif self.sep_style == SeparatorStyle.CHATML:
+            ret = "" if system_prompt == "" else system_prompt + self.sep + "\n"
+            for role, message in self.messages:
+                if message:
+                    ret += role + "\n" + message + self.sep + "\n"
+                else:
+                    ret += role + "\n"
+            return ret
+        elif self.sep_style == SeparatorStyle.CHATGLM3:
+            ret = ""
+            if self.system_message:
+                ret += system_prompt
+            for role, message in self.messages:
+                if message:
+                    ret += role + "\n" + message
+                else:
+                    ret += role
+            return ret
+        elif self.sep_style == SeparatorStyle.CHATINTERN:
+            # source: https://huggingface.co/internlm/internlm-chat-7b-8k/blob/bd546fa984b4b0b86958f56bf37f94aa75ab8831/modeling_internlm.py#L771
+            seps = [self.sep, self.sep2]
+            ret = system_prompt
+            for i, (role, message) in enumerate(self.messages):
+                if i % 2 == 0:
+                    ret += "<s>"
+                if message:
+                    ret += role + ":" + message + seps[i % 2] + "\n"
+                else:
+                    ret += role + ":"
+            return ret
+        elif self.sep_style == SeparatorStyle.DOLLY:
+            seps = [self.sep, self.sep2]
+            ret = system_prompt
+            for i, (role, message) in enumerate(self.messages):
+                if message:
+                    ret += role + ":\n" + message + seps[i % 2]
+                    if i % 2 == 1:
+                        ret += "\n\n"
+                else:
+                    ret += role + ":\n"
+            return ret
+        elif self.sep_style == SeparatorStyle.PHOENIX:
+            ret = system_prompt
+            for role, message in self.messages:
+                if message:
+                    ret += role + ": " + "<s>" + message + "</s>"
+                else:
+                    ret += role + ": " + "<s>"
+            return ret
+        elif self.sep_style == SeparatorStyle.ROBIN:
+            ret = system_prompt + self.sep
+            for role, message in self.messages:
+                if message:
+                    ret += role + ":\n" + message + self.sep
+                else:
+                    ret += role + ":\n"
+            return ret
+        elif self.sep_style == SeparatorStyle.FALCON_CHAT:
+            ret = ""
+            if self.system_message:
+                ret += system_prompt + self.sep
+            for role, message in self.messages:
+                if message:
+                    ret += role + ": " + message + self.sep
+                else:
+                    ret += role + ":"
+            return ret
+        elif self.sep_style == SeparatorStyle.METAMATH:
+            ret = "" if system_prompt == "" else system_prompt + self.sep
+            for i, (role, message) in enumerate(self.messages):
+                # For MetaMath, sep2 is used to prefix the message.
+                starting_sep = ":\n" if i % 2 == 0 else ": " + self.sep2
+                ending_sep = self.sep if i % 2 == 0 else ""
+                if message:
+                    ret += role + starting_sep + message + ending_sep
+                else:
+                    ret += role + starting_sep
+            return ret
+        elif self.sep_style == SeparatorStyle.DEEPSEEK_CHAT:
+            seps = [self.sep, self.sep2]
+            ret = system_prompt
+            for i, (role, message) in enumerate(self.messages):
+                if message:
+                    ret += role + ": " + message + seps[i % 2]
+                else:
+                    ret += role + ":"
+            return ret
+        else:
+            raise ValueError(f"Invalid style: {self.sep_style}")
+
+    def set_system_message(self, system_message: str):
+        """Set the system message."""
+        self.system_message = system_message
+
+    def append_message(self, role: str, message: str):
+        """Append a new message."""
+        self.messages.append([role, message])
+
+    def update_last_message(self, message: str):
+        """Update the last output.
+
+        The last message is typically set to be None when constructing the prompt,
+        so we need to update it in-place after getting the response from a model.
+        """
+        self.messages[-1][1] = message
+
+    def to_gradio_chatbot(self):
+        """Convert the conversation to gradio chatbot format."""
+        ret = []
+        for i, (role, msg) in enumerate(self.messages[self.offset :]):
+            if i % 2 == 0:
+                ret.append([msg, None])
+            else:
+                ret[-1][-1] = msg
+        return ret
+
+    def to_openai_api_messages(self):
+        """Convert the conversation to OpenAI chat completion format."""
+        if self.system_message == "":
+            ret = []
+        else:
+            ret = [{"role": "system", "content": self.system_message}]
+
+        for i, (_, msg) in enumerate(self.messages[self.offset :]):
+            if i % 2 == 0:
+                ret.append({"role": "user", "content": msg})
+            else:
+                if msg is not None:
+                    ret.append({"role": "assistant", "content": msg})
+        return ret
+
+    def copy(self):
+        return Conversation(
+            name=self.name,
+            system_template=self.system_template,
+            system_message=self.system_message,
+            roles=self.roles,
+            messages=[[x, y] for x, y in self.messages],
+            offset=self.offset,
+            sep_style=self.sep_style,
+            sep=self.sep,
+            sep2=self.sep2,
+            stop_str=self.stop_str,
+        )
+
+    def dict(self):
+        return {
+            "template_name": self.name,
+            "system_message": self.system_message,
+            "roles": self.roles,
+            "messages": self.messages,
+            "offset": self.offset,
+        }
+
+
+# A global registry for all conversation templates
+chat_templates: Dict[str, Conversation] = {}
+
+
+def register_conv_template(template: Conversation, override: bool = False):
+    """Register a new conversation template."""
+    if not override:
+        assert template.name not in chat_templates, f"{template.name} has been registered."
+
+    chat_templates[template.name] = template
+
+
+def chat_template_exists(template_name: str) -> bool:
+    return template_name in chat_templates
+
+
+def generate_chat_conv(request: ChatCompletionRequest, template_name: str) -> Conversation:
+    conv = chat_templates[template_name].copy()
+    conv = Conversation(
+        name=conv.name,
+        system_template=conv.system_template,
+        system_message=conv.system_message,
+        roles=conv.roles,
+        messages=list(conv.messages),  # prevent in-place modification
+        offset=conv.offset,
+        sep_style=SeparatorStyle(conv.sep_style),
+        sep=conv.sep,
+        sep2=conv.sep2,
+        stop_str=conv.stop_str,
+    )
+
+    if isinstance(request.messages, str):
+        raise ValueError("The messages should be a list of dict.")
+    for message in request.messages:
+        msg_role = message["role"]
+        if msg_role == "system":
+            conv.system_message = message["content"]
+        elif msg_role == "user":
+            conv.append_message(conv.roles[0], message["content"])
+        elif msg_role == "assistant":
+            conv.append_message(conv.roles[1], message["content"])
+        else:
+            raise ValueError(f"Unknown role: {msg_role}")
+
+    # Add a blank message for the assistant.
+    conv.append_message(conv.roles[1], None)
+
+    return conv
+
+
+# llama2 template
+# reference: https://huggingface.co/blog/codellama#conversational-instructions
+# reference: https://github.com/facebookresearch/llama/blob/1a240688810f8036049e8da36b073f63d2ac552c/llama/generation.py#L212
+register_conv_template(
+    Conversation(
+        name="llama-2",
+        system_template="[INST] <<SYS>>\n{system_message}\n<</SYS>>\n\n",
+        roles=("[INST]", "[/INST]"),
+        sep_style=SeparatorStyle.LLAMA2,
+        sep=" ",
+        sep2=" </s><s>",
+        stop_str=["[INST]", "[/INST]", "<<SYS>>", "<</SYS>>"],
+    )
+)
+
+register_conv_template(
+    Conversation(
+        name="chatml",
+        system_template="<|im_start|>system\n{system_message}",
+        system_message="You are an AI assistant.",
+        roles=("<|im_start|>user", "<|im_start|>assistant"),
+        sep_style=SeparatorStyle.CHATML,
+        sep="<|im_end|>",
+        stop_str=["<|endoftext|>", "<|im_end|>"],
+    )
+)

python/sglang/srt/managers/openai_protocol.py

@@ -65,3 +65,59 @@ class CompletionStreamResponse(BaseModel):
     created: int = Field(default_factory=lambda: int(time.time()))
     model: str
     choices: List[CompletionResponseStreamChoice]
+    usage: UsageInfo
+
+
+class ChatCompletionRequest(BaseModel):
+    model: str
+    messages: Union[str, List[Dict[str, str]]]
+    temperature: Optional[float] = 0.7
+    top_p: Optional[float] = 1.0
+    n: Optional[int] = 1
+    max_tokens: Optional[int] = 16
+    stop: Optional[Union[str, List[str]]] = Field(default_factory=list)
+    stream: Optional[bool] = False
+    presence_penalty: Optional[float] = 0.0
+    frequency_penalty: Optional[float] = 0.0
+    logit_bias: Optional[Dict[str, float]] = None
+    user: Optional[str] = None
+    best_of: Optional[int] = None
+
+
+class ChatMessage(BaseModel):
+    role: Optional[str] = None
+    content: Optional[str] = None
+
+
+class ChatCompletionResponseChoice(BaseModel):
+    index: int
+    message: ChatMessage
+    finish_reason: Optional[str] = None
+
+
+class ChatCompletionResponse(BaseModel):
+    id: str
+    object: str = "chat.completion"
+    created: int = Field(default_factory=lambda: int(time.time()))
+    model: str
+    choices: List[ChatCompletionResponseChoice]
+    usage: UsageInfo
+
+
+class DeltaMessage(BaseModel):
+    role: Optional[str] = None
+    content: Optional[str] = None
+
+
+class ChatCompletionResponseStreamChoice(BaseModel):
+    index: int
+    delta: DeltaMessage
+    finish_reason: Optional[str] = None
+
+
+class ChatCompletionStreamResponse(BaseModel):
+    id: str
+    object: str = "chat.completion.chunk"
+    created: int = Field(default_factory=lambda: int(time.time()))
+    model: str
+    choices: List[ChatCompletionResponseStreamChoice]

python/sglang/srt/server.py

@@ -2,6 +2,7 @@
 import asyncio
 import json
 import multiprocessing as mp
+import os
 import sys
 import threading
 import time
@@ -17,15 +18,29 @@ import uvloop
 from fastapi import FastAPI, Request
 from fastapi.responses import StreamingResponse
 from sglang.backend.runtime_endpoint import RuntimeEndpoint
+from sglang.srt.conversation import (
+    Conversation,
+    SeparatorStyle,
+    chat_template_exists,
+    generate_chat_conv,
+    register_conv_template,
+)
 from sglang.srt.managers.detokenizer_manager import start_detokenizer_process
 from sglang.srt.managers.io_struct import GenerateReqInput
 from sglang.srt.managers.openai_protocol import (
+    ChatCompletionRequest,
+    ChatCompletionResponse,
+    ChatCompletionResponseChoice,
+    ChatCompletionResponseStreamChoice,
+    ChatCompletionStreamResponse,
+    ChatMessage,
     CompletionRequest,
     CompletionResponse,
     CompletionResponseChoice,
     CompletionResponseStreamChoice,
     CompletionStreamResponse,
-    UsageInfo
+    DeltaMessage,
+    UsageInfo,
 )
 from sglang.srt.managers.router.manager import start_router_process
 from sglang.srt.managers.tokenizer_manager import TokenizerManager
@@ -37,6 +52,7 @@ asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())
 
 app = FastAPI()
 tokenizer_manager = None
+chat_template_name = None
 
 
 @app.get("/get_model_info")
@@ -46,6 +62,7 @@ async def get_model_info():
     }
     return result
 
+
 async def stream_generator(obj):
     async for out in tokenizer_manager.generate_request(obj):
         yield out
@@ -61,7 +78,7 @@ async def generate_request(obj: GenerateReqInput):
             async for out in stream_generator(obj):
                 yield f"data: {json.dumps(out, ensure_ascii=False)}\n\n"
             yield "data: [DONE]\n\n"
-        
+
         return StreamingResponse(stream_results(), media_type="text/event-stream")
 
     ret = await tokenizer_manager.generate_request(obj).__anext__()
@@ -91,11 +108,15 @@ async def v1_completions(raw_request: Request):
     adapted_request.post_init()
 
     if adapted_request.stream:
+
         async def gnerate_stream_resp():
             stream_buffer = ""
             async for content in stream_generator(adapted_request):
                 text = content["text"]
-                delta = text[len(stream_buffer):]
+                prompt_tokens = content["meta_info"]["prompt_tokens"]
+                completion_tokens = content["meta_info"]["completion_tokens"]
+
+                delta = text[len(stream_buffer) :]
                 stream_buffer = text
                 choice_data = CompletionResponseStreamChoice(
                     index=0,
@@ -108,12 +129,17 @@ async def v1_completions(raw_request: Request):
                     object="text_completion",
                     choices=[choice_data],
                     model=request.model,
+                    usage=UsageInfo(
+                        prompt_tokens=prompt_tokens,
+                        completion_tokens=completion_tokens,
+                        total_tokens=prompt_tokens + completion_tokens,
+                    ),
                 )
                 yield f"data: {chunk.json(exclude_unset=True, ensure_ascii=False)}\n\n"
+            yield "data: [DONE]\n\n"
 
         return StreamingResponse(gnerate_stream_resp(), media_type="text/event-stream")
 
-
     # Non-streaming response.
     ret = await generate_request(adapted_request)
 
@@ -121,7 +147,7 @@ async def v1_completions(raw_request: Request):
         index=0,
         text=ret["text"],
         logprobs=None,
-        finish_reason=None, # TODO(comaniac): Add finish reason.
+        finish_reason=None,  # TODO(comaniac): Add finish reason.
     )
 
     prompt_tokens = ret["meta_info"]["prompt_tokens"]
@@ -139,8 +165,108 @@ async def v1_completions(raw_request: Request):
     return response
 
 
+@app.post("/v1/chat/completions")
+async def v1_chat_completions(raw_request: Request):
+    request_json = await raw_request.json()
+    request = ChatCompletionRequest(**request_json)
+
+    # TODO: Validate the request and return HTTPStatus.BAD_REQUEST if invalid.
+    assert request.n == 1
+
+    if not isinstance(request.messages, str):
+        # Apply chat template and its stop strings.
+        if chat_template_name is None:
+            prompt = tokenizer_manager.tokenizer.apply_chat_template(
+                request.messages, tokenize=False, add_generation_prompt=True
+            )
+            stop = request.stop
+        else:
+            conv = generate_chat_conv(request, chat_template_name)
+            prompt = conv.get_prompt()
+            stop = conv.stop_str or []
+            if request.stop:
+                if isinstance(request.stop, str):
+                    stop.append(request.stop)
+                else:
+                    stop.extend(request.stop)
+    else:
+        # Use the raw prompt and stop strings if the messages is already a string.
+        prompt = request.messages
+        stop = request.stop
+
+    adapted_request = GenerateReqInput(
+        text=prompt,
+        sampling_params={
+            "temperature": request.temperature,
+            "max_new_tokens": request.max_tokens,
+            "stop": stop,
+            "top_p": request.top_p,
+            "presence_penalty": request.presence_penalty,
+            "frequency_penalty": request.frequency_penalty,
+        },
+        stream=request.stream,
+    )
+    adapted_request.post_init()
+
+    if adapted_request.stream:
+
+        async def gnerate_stream_resp():
+            is_first = True
+
+            stream_buffer = ""
+            async for content in stream_generator(adapted_request):
+                if is_first:
+                    # First chunk with role
+                    is_first = False
+                    choice_data = ChatCompletionResponseStreamChoice(
+                        index=0,
+                        delta=DeltaMessage(role="assistant"),
+                        finish_reason=None,
+                    )
+                    chunk = ChatCompletionStreamResponse(
+                        id=content["meta_info"]["id"], choices=[choice_data], model=request.model
+                    )
+                    yield f"data: {chunk.json(exclude_unset=True, ensure_ascii=False)}\n\n"
+
+                text = content["text"]
+                delta = text[len(stream_buffer) :]
+                stream_buffer = text
+                choice_data = ChatCompletionResponseStreamChoice(
+                    index=0, delta=DeltaMessage(content=delta), finish_reason=None
+                )
+                chunk = ChatCompletionStreamResponse(
+                    id=content["meta_info"]["id"], choices=[choice_data], model=request.model
+                )
+                yield f"data: {chunk.json(exclude_unset=True, ensure_ascii=False)}\n\n"
+            yield "data: [DONE]\n\n"
+
+        return StreamingResponse(gnerate_stream_resp(), media_type="text/event-stream")
+
+    # Non-streaming response.
+    ret = await generate_request(adapted_request)
+    prompt_tokens = ret["meta_info"]["prompt_tokens"]
+    completion_tokens = ret["meta_info"]["completion_tokens"]
+    choice_data = ChatCompletionResponseChoice(
+        index=0,
+        message=ChatMessage(role="assistant", content=ret["text"]),
+        finish_reason=None,  # TODO(comaniac): Add finish reason.
+    )
+    response = ChatCompletionResponse(
+        id=ret["meta_info"]["id"],
+        model=request.model,
+        choices=[choice_data],
+        usage=UsageInfo(
+            prompt_tokens=prompt_tokens,
+            completion_tokens=completion_tokens,
+            total_tokens=prompt_tokens + completion_tokens,
+        ),
+    )
+    return response
+
+
 def launch_server(server_args, pipe_finish_writer):
     global tokenizer_manager
+    global chat_template_name
 
     # Allocate ports
     can_use_ports = alloc_usable_network_port(
@@ -154,6 +280,36 @@ def launch_server(server_args, pipe_finish_writer):
         model_rpc_ports=can_use_ports[4:],
     )
 
+    # Load chat template if needed
+    if server_args.chat_template is not None:
+        if not chat_template_exists(server_args.chat_template):
+            if not os.path.exists(server_args.chat_template):
+                raise RuntimeError(
+                    f"Chat template {server_args.chat_template} is not a built-in template name "
+                    "or a valid chat template file path."
+                )
+            with open(server_args.chat_template, "r") as filep:
+                template = json.load(filep)
+                try:
+                    sep_style = SeparatorStyle[template["sep_style"]]
+                except KeyError:
+                    raise ValueError(f"Unknown separator style: {template['sep_style']}") from None
+                register_conv_template(
+                    Conversation(
+                        name=template["name"],
+                        system_template=template["system"] + "\n{system_message}",
+                        system_message=template.get("system_message", ""),
+                        roles=(template["user"], template["assistant"]),
+                        sep_style=sep_style,
+                        sep=template.get("sep", "\n"),
+                        stop_str=template["stop_str"],
+                    ),
+                    override=True,
+                )
+            chat_template_name = template["name"]
+        else:
+            chat_template_name = server_args.chat_template
+
     # Launch processes
     tokenizer_manager = TokenizerManager(server_args, port_args)
     pipe_router_reader, pipe_router_writer = mp.Pipe(duplex=False)

python/sglang/srt/server_args.py

@@ -11,6 +11,7 @@ class ServerArgs:
     port: int = 30000
     load_format: str = "auto"
     tokenizer_mode: str = "auto"
+    chat_template: Optional[str] = None
     trust_remote_code: bool = True
     mem_fraction_static: Optional[float] = None
     tp_size: int = 1
@@ -77,6 +78,12 @@ class ServerArgs:
             "tokenizer if available, and 'slow' will "
             "always use the slow tokenizer.",
         )
+        parser.add_argument(
+            "--chat-template",
+            type=str,
+            default=ServerArgs.chat_template,
+            help="The buliltin chat template name or the path of the chat template file. This is only used for OpenAI-compatible API server",
+        )
         parser.add_argument(
             "--trust-remote-code",
             action="store_true",

test/srt/test_openai_server.py

 """
-python3 -m sglang.launch_server --model-path TinyLlama/TinyLlama-1.1B-Chat-v0.4 --port 30000
+First run the following command to launch the server.
+Note that TinyLlama adopts different chat templates in different versions.
+For v0.4, the chat template is chatml.
 
-Output:
-The capital of France is Paris.\nThe capital of the United States is Washington, D.C.\nThe capital of Canada is Ottawa.\nThe capital of Japan is Tokyo
+python3 -m sglang.launch_server --model-path TinyLlama/TinyLlama-1.1B-Chat-v0.4 \
+--port 30000 --chat-template chatml
+
+Output example:
+The capital of France is Paris.
+The capital of the United States is Washington, D.C.
+The capital of Canada is Ottawa.
+The capital of Japan is Tokyo
 """
 
 import argparse
@@ -38,13 +46,57 @@ def test_completion_stream(args):
     for r in response:
         print(r.choices[0].text, end="", flush=True)
         assert r.id
-        assert r.created
         assert r.usage.prompt_tokens > 0
         assert r.usage.completion_tokens > 0
         assert r.usage.total_tokens > 0
     print()
 
 
+def test_chat_completion(args):
+    client = openai.Client(api_key="EMPTY", base_url=args.base_url)
+    response = client.chat.completions.create(
+        model="default",
+        messages=[
+            {"role": "system", "content": "You are a helpful AI assistant"},
+            {"role": "user", "content": "What is the capital of France?"},
+        ],
+        temperature=0,
+        max_tokens=32,
+    )
+    print(response.choices[0].message.content)
+    assert response.id
+    assert response.created
+    assert response.usage.prompt_tokens > 0
+    assert response.usage.completion_tokens > 0
+    assert response.usage.total_tokens > 0
+
+
+def test_chat_completion_stream(args):
+    client = openai.Client(api_key="EMPTY", base_url=args.base_url)
+    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,
+        stream=True,
+    )
+    is_first = True
+    for chunk in response:
+        if is_first:
+            is_first = False
+            assert chunk.choices[0].delta.role == "assistant"
+            continue
+
+        data = chunk.choices[0].delta
+        if not data.content:
+            continue
+        print(data.content, end="", flush=True)
+    print()
+
+
 if __name__ == "__main__":
     parser = argparse.ArgumentParser()
     parser.add_argument("--base-url", type=str, default="http://127.0.0.1:30000/v1")
@@ -52,3 +104,5 @@ if __name__ == "__main__":
 
     test_completion(args)
     test_completion_stream(args)
+    test_chat_completion(args)
+    test_chat_completion_stream(args)