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Two SSE streams live behind this server:
POST /generate — submit a prompt, stream back token deltas
POST /v1/completions — OpenAI-compatible streaming completions
GET /engine/events — stream of engine-state snapshots (one per step)
— what the demo page subscribes to
GET /engine/snapshot — one-shot current state (JSON)
GET / — static demo page
The demo page subscribes to /engine/events and renders the block pool,
scheduler queues, and live token streams.
"""
from __future__ import annotations
import argparse
import asyncio
import json
import os
import time
from pathlib import Path
from typing import AsyncIterator, Optional
from fastapi import FastAPI, HTTPException, Request
from fastapi.responses import FileResponse, JSONResponse, StreamingResponse
from fastapi.staticfiles import StaticFiles
from pydantic import BaseModel, Field
from .config import EngineConfig, SamplingParams
from .engine import LLMEngine
# ---------------------------------------------------------------------------
# Schemas
# ---------------------------------------------------------------------------
class GenerateRequest(BaseModel):
prompt: str
max_tokens: int = 64
temperature: float = 1.0
top_p: float = 1.0
top_k: int = -1
seed: Optional[int] = None
ignore_eos: bool = False
stream: bool = True
class CompletionsRequest(BaseModel):
model: Optional[str] = None
prompt: str | list[str]
max_tokens: int = 64
temperature: float = 1.0
top_p: float = 1.0
n: int = 1
stream: bool = False
stop: Optional[list[str]] = None
seed: Optional[int] = None
# ---------------------------------------------------------------------------
# App factory
# ---------------------------------------------------------------------------
def _sse(data: dict | str) -> bytes:
if isinstance(data, dict):
data = json.dumps(data, separators=(",", ":"))
return f"data: {data}\n\n".encode("utf-8")
def build_app(config: EngineConfig) -> FastAPI:
app = FastAPI(title="tiny_vllm", version="0.1.0")
engine = LLMEngine(config)
@app.on_event("startup")
async def _on_startup() -> None:
await engine.startup()
@app.on_event("shutdown")
async def _on_shutdown() -> None:
await engine.shutdown()
# ---- root + static -------------------------------------------------
static_dir = Path(__file__).parent.parent / "web"
if static_dir.exists():
app.mount("/static", StaticFiles(directory=str(static_dir)), name="static")
@app.get("/")
async def root() -> FileResponse:
return FileResponse(str(static_dir / "index.html"))
else:
@app.get("/")
async def root() -> dict:
return {"name": "tiny_vllm", "status": "ok",
"hint": "demo page not found; POST to /generate"}
# ---- introspection -------------------------------------------------
@app.get("/engine/snapshot")
async def snapshot() -> dict:
return engine.snapshot()
@app.get("/engine/events")
async def events(request: Request) -> StreamingResponse:
q = engine.subscribe_events()
async def gen() -> AsyncIterator[bytes]:
# Push initial snapshot so a freshly-connected client has state.
yield _sse({"type": "snapshot", "payload": engine.snapshot()})
try:
while True:
if await request.is_disconnected():
break
try:
ev = await asyncio.wait_for(q.get(), timeout=15.0)
except asyncio.TimeoutError:
yield b": keepalive\n\n"
continue
yield _sse({
"type": ev.type,
"step": ev.step,
"timestamp": ev.timestamp,
"payload": ev.payload,
})
finally:
engine.unsubscribe_events(q)
return StreamingResponse(gen(), media_type="text/event-stream")
# ---- generation ----------------------------------------------------
def _params(req: GenerateRequest) -> SamplingParams:
return SamplingParams(
max_tokens=req.max_tokens,
temperature=req.temperature,
top_p=req.top_p,
top_k=req.top_k,
seed=req.seed,
ignore_eos=req.ignore_eos,
)
@app.post("/generate")
async def generate(req: GenerateRequest, request: Request) -> StreamingResponse | JSONResponse:
try:
rid = engine.add_request(req.prompt, _params(req))
except ValueError as e:
raise HTTPException(status_code=400, detail=str(e))
if not req.stream:
text_parts: list[str] = []
finish_reason: Optional[str] = None
async for item in engine.stream(rid):
text_parts.append(item.new_text)
if item.finished:
finish_reason = item.finish_reason
break
return JSONResponse({
"request_id": rid,
"text": "".join(text_parts),
"finish_reason": finish_reason,
})
async def gen() -> AsyncIterator[bytes]:
try:
async for item in engine.stream(rid):
if await request.is_disconnected():
engine.abort(rid)
break
yield _sse({
"request_id": rid,
"text": item.new_text,
"finished": item.finished,
"finish_reason": item.finish_reason,
})
if item.finished:
yield b"data: [DONE]\n\n"
break
except asyncio.CancelledError:
engine.abort(rid)
raise
return StreamingResponse(gen(), media_type="text/event-stream")
@app.post("/v1/completions")
async def completions(req: CompletionsRequest, request: Request):
# Single-prompt only (n=1) for the minimal impl.
if isinstance(req.prompt, list):
if len(req.prompt) != 1:
raise HTTPException(400, "tiny_vllm only supports a single prompt per call")
prompt = req.prompt[0]
else:
prompt = req.prompt
try:
rid = engine.add_request(
prompt,
SamplingParams(
max_tokens=req.max_tokens,
temperature=req.temperature,
top_p=req.top_p,
seed=req.seed,
),
)
except ValueError as e:
raise HTTPException(400, str(e))
created = int(time.time())
model_id = req.model or config.model
if not req.stream:
text_parts: list[str] = []
finish_reason: Optional[str] = None
async for item in engine.stream(rid):
text_parts.append(item.new_text)
if item.finished:
finish_reason = item.finish_reason
break
return JSONResponse({
"id": f"cmpl-{rid}",
"object": "text_completion",
"created": created,
"model": model_id,
"choices": [{
"text": "".join(text_parts),
"index": 0,
"logprobs": None,
"finish_reason": finish_reason,
}],
})
async def gen() -> AsyncIterator[bytes]:
try:
async for item in engine.stream(rid):
if await request.is_disconnected():
engine.abort(rid)
break
chunk = {
"id": f"cmpl-{rid}",
"object": "text_completion",
"created": created,
"model": model_id,
"choices": [{
"text": item.new_text,
"index": 0,
"logprobs": None,
"finish_reason": item.finish_reason if item.finished else None,
}],
}
yield _sse(chunk)
if item.finished:
yield b"data: [DONE]\n\n"
break
except asyncio.CancelledError:
engine.abort(rid)
raise
return StreamingResponse(gen(), media_type="text/event-stream")
@app.post("/abort/{request_id}")
async def abort(request_id: str) -> dict:
ok = engine.abort(request_id)
return {"aborted": ok}
return app
# ---------------------------------------------------------------------------
# CLI entry
# ---------------------------------------------------------------------------
def main() -> None:
parser = argparse.ArgumentParser(description="tiny_vllm server")
parser.add_argument("--model", default=os.environ.get("TINY_VLLM_MODEL", "Qwen/Qwen2.5-0.5B-Instruct"))
parser.add_argument("--device", default=os.environ.get("TINY_VLLM_DEVICE", "cpu"))
parser.add_argument("--dtype", default=os.environ.get("TINY_VLLM_DTYPE", "float32"))
parser.add_argument("--block-size", type=int, default=16)
parser.add_argument("--num-blocks", type=int, default=256)
parser.add_argument("--max-num-seqs", type=int, default=8)
parser.add_argument("--max-num-batched-tokens", type=int, default=512)
parser.add_argument("--max-model-len", type=int, default=2048)
parser.add_argument("--disable-prefix-caching", action="store_true")
parser.add_argument("--record", default=None,
help="Append every engine event to this JSONL file "
"(e.g. web/events.jsonl) to power the static replay demo.")
parser.add_argument("--host", default="0.0.0.0")
parser.add_argument("--port", type=int, default=8000)
args = parser.parse_args()
cfg = EngineConfig(
model=args.model,
device=args.device,
dtype=args.dtype,
block_size=args.block_size,
num_blocks=args.num_blocks,
max_num_seqs=args.max_num_seqs,
max_num_batched_tokens=args.max_num_batched_tokens,
max_model_len=args.max_model_len,
enable_prefix_caching=not args.disable_prefix_caching,
record_path=args.record,
)
import uvicorn
app = build_app(cfg)
uvicorn.run(app, host=args.host, port=args.port, log_level="info")
if __name__ == "__main__":
main()
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