Disaggregated Serving¶

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""
This file provides a disaggregated prefilling proxy demo to demonstrate an
example usage of XpYd disaggregated prefilling.
We can launch multiple vllm instances (2 for prefill and 2 for decode), and
launch this proxy demo through:
  python3 examples/disaggregated/disaggregated_serving/disagg_proxy_demo.py  \
       --model $model_name  \
       --prefill localhost:8100 localhost:8101   \
       --decode localhost:8200 localhost:8201   \
       --port 8000

Note: This demo will be removed once the PDController implemented in PR 15343
(https://github.com/vllm-project/vllm/pull/15343) supports XpYd.
"""

import argparse
import ipaddress
import itertools
import json
import logging
import os
import sys
from abc import ABC, abstractmethod
from collections.abc import Callable

import aiohttp
import requests
import uvicorn
from fastapi import APIRouter, Depends, FastAPI, Header, HTTPException, Request, status
from fastapi.responses import JSONResponse, StreamingResponse

AIOHTTP_TIMEOUT = aiohttp.ClientTimeout(total=6 * 60 * 60)
logger = logging.getLogger()
logging.basicConfig(level=logging.INFO)


class SchedulingPolicy(ABC):
    @abstractmethod
    def schedule(self, cycler: itertools.cycle):
        raise NotImplementedError("Scheduling Proxy is not set.")


class Proxy:
    def __init__(
        self,
        prefill_instances: list[str],
        decode_instances: list[str],
        model: str,
        scheduling_policy: SchedulingPolicy,
        custom_create_completion: Callable[[Request], StreamingResponse] | None = None,
        custom_create_chat_completion: Callable[[Request], StreamingResponse]
        | None = None,
    ):
        self.prefill_instances = prefill_instances
        self.decode_instances = decode_instances
        self.prefill_cycler = itertools.cycle(prefill_instances)
        self.decode_cycler = itertools.cycle(decode_instances)
        self.model = model
        self.scheduling_policy = scheduling_policy
        self.custom_create_completion = custom_create_completion
        self.custom_create_chat_completion = custom_create_chat_completion
        self.router = APIRouter()
        self.setup_routes()

    def setup_routes(self):
        self.router.post(
            "/v1/completions", dependencies=[Depends(self.validate_json_request)]
        )(
            self.custom_create_completion
            if self.custom_create_completion
            else self.create_completion
        )
        self.router.post(
            "/v1/chat/completions", dependencies=[Depends(self.validate_json_request)]
        )(
            self.custom_create_chat_completion
            if self.custom_create_chat_completion
            else self.create_chat_completion
        )
        self.router.get("/status", response_class=JSONResponse)(self.get_status)
        self.router.post(
            "/instances/add", dependencies=[Depends(self.api_key_authenticate)]
        )(self.add_instance_endpoint)

    async def validate_json_request(self, raw_request: Request):
        content_type = raw_request.headers.get("content-type", "").lower()
        if content_type != "application/json":
            raise HTTPException(
                status_code=415,
                detail="Unsupported Media Type: Only 'application/json' is allowed",
            )

    def api_key_authenticate(self, x_api_key: str = Header(...)):
        expected_api_key = os.environ.get("ADMIN_API_KEY")
        if not expected_api_key:
            logger.error("ADMIN_API_KEY is not set in the environment.")
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail="Server configuration error.",
            )
        if x_api_key != expected_api_key:
            logger.warning("Unauthorized access attempt with API Key: %s", x_api_key)
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail="Forbidden: Invalid API Key.",
            )

    async def validate_instance(self, instance: str) -> bool:
        url = f"http://{instance}/v1/models"
        try:
            async with aiohttp.ClientSession(timeout=AIOHTTP_TIMEOUT) as client:
                logger.info("Verifying %s ...", instance)
                async with client.get(url) as response:
                    if response.status == 200:
                        data = await response.json()
                        if "data" in data and len(data["data"]) > 0:
                            model_cur = data["data"][0].get("id", "")
                            if model_cur == self.model:
                                logger.info("Instance: %s could be added.", instance)
                                return True
                            else:
                                logger.warning(
                                    "Mismatch model %s : %s != %s",
                                    instance,
                                    model_cur,
                                    self.model,
                                )
                                return False
                        else:
                            return False
                    else:
                        return False
        except aiohttp.ClientError as e:
            logger.error(str(e))
            return False
        except Exception as e:
            logger.error(str(e))
            return False

    async def add_instance_endpoint(self, request: Request):
        try:
            data = await request.json()
            logger.warning(str(data))
            instance_type = data.get("type")
            instance = data.get("instance")
            if instance_type not in ["prefill", "decode"]:
                raise HTTPException(status_code=400, detail="Invalid instance type.")
            if not instance or ":" not in instance:
                raise HTTPException(status_code=400, detail="Invalid instance format.")
            host, port_str = instance.split(":")
            try:
                if host != "localhost":
                    ipaddress.ip_address(host)
                port = int(port_str)
                if not (0 < port < 65536):
                    raise HTTPException(status_code=400, detail="Invalid port number.")
            except Exception as e:
                raise HTTPException(
                    status_code=400, detail="Invalid instance address."
                ) from e

            is_valid = await self.validate_instance(instance)
            if not is_valid:
                raise HTTPException(
                    status_code=400, detail="Instance validation failed."
                )

            if instance_type == "prefill":
                if instance not in self.prefill_instances:
                    self.prefill_instances.append(instance)
                    self.prefill_cycler = itertools.cycle(self.prefill_instances)
                else:
                    raise HTTPException(
                        status_code=400, detail="Instance already exists."
                    )
            else:
                if instance not in self.decode_instances:
                    self.decode_instances.append(instance)
                    self.decode_cycler = itertools.cycle(self.decode_instances)
                else:
                    raise HTTPException(
                        status_code=400, detail="Instance already exists."
                    )

            return JSONResponse(
                content={"message": f"Added {instance} to {instance_type}_instances."}
            )
        except HTTPException as http_exc:
            raise http_exc
        except Exception as e:
            logger.error("Error in add_instance_endpoint: %s", str(e))
            raise HTTPException(status_code=500, detail=str(e)) from e

    async def forward_request(self, url, data, use_chunked=True):
        async with aiohttp.ClientSession(timeout=AIOHTTP_TIMEOUT) as session:
            headers = {"Authorization": f"Bearer {os.environ.get('OPENAI_API_KEY')}"}
            try:
                async with session.post(
                    url=url, json=data, headers=headers
                ) as response:
                    if 200 <= response.status < 300 or 400 <= response.status < 500:
                        if use_chunked:
                            async for chunk_bytes in response.content.iter_chunked(
                                1024
                            ):
                                yield chunk_bytes
                        else:
                            content = await response.read()
                            yield content
                    else:
                        error_content = await response.text()
                        try:
                            error_content = json.loads(error_content)
                        except json.JSONDecodeError:
                            error_content = error_content
                        logger.error(
                            "Request failed with status %s: %s",
                            response.status,
                            error_content,
                        )
                        raise HTTPException(
                            status_code=response.status,
                            detail=f"Request failed with status {response.status}: "
                            f"{error_content}",
                        )
            except aiohttp.ClientError as e:
                logger.error("ClientError occurred: %s", str(e))
                raise HTTPException(
                    status_code=502,
                    detail="Bad Gateway: Error communicating with upstream server.",
                ) from e
            except Exception as e:
                logger.error("Unexpected error: %s", str(e))
                raise HTTPException(status_code=500, detail=str(e)) from e

    def schedule(self, cycler: itertools.cycle) -> str:
        return self.scheduling_policy.schedule(cycler)

    async def get_status(self):
        status = {
            "prefill_node_count": len(self.prefill_instances),
            "decode_node_count": len(self.decode_instances),
            "prefill_nodes": self.prefill_instances,
            "decode_nodes": self.decode_instances,
        }
        return status

    async def create_completion(self, raw_request: Request):
        try:
            request = await raw_request.json()

            kv_prepare_request = request.copy()
            kv_prepare_request["max_tokens"] = 1

            prefill_instance = self.schedule(self.prefill_cycler)
            try:
                async for _ in self.forward_request(
                    f"http://{prefill_instance}/v1/completions", kv_prepare_request
                ):
                    continue
            except HTTPException as http_exc:
                self.remove_instance_endpoint("prefill", prefill_instance)
                raise http_exc

            # Perform kv recv and decoding stage
            decode_instance = self.schedule(self.decode_cycler)

            try:
                generator = self.forward_request(
                    f"http://{decode_instance}/v1/completions", request
                )
            except HTTPException as http_exc:
                self.remove_instance_endpoint("decode", decode_instance)
                raise http_exc
            response = StreamingResponse(generator)
            return response
        except Exception:
            import sys

            exc_info = sys.exc_info()
            print("Error occurred in disagg proxy server")
            print(exc_info)

    async def create_chat_completion(self, raw_request: Request):
        try:
            request = await raw_request.json()

            # add params to request
            kv_prepare_request = request.copy()
            kv_prepare_request["max_tokens"] = 1
            if "max_completion_tokens" in kv_prepare_request:
                kv_prepare_request["max_completion_tokens"] = 1

            # prefill stage
            prefill_instance = self.schedule(self.prefill_cycler)
            try:
                async for _ in self.forward_request(
                    f"http://{prefill_instance}/v1/chat/completions", kv_prepare_request
                ):
                    continue
            except HTTPException as http_exc:
                self.remove_instance_endpoint("prefill", prefill_instance)
                raise http_exc
            # Perform kv recv and decoding stage
            decode_instance = self.schedule(self.decode_cycler)

            try:
                generator = self.forward_request(
                    "http://" + decode_instance + "/v1/chat/completions", request
                )
            except HTTPException as http_exc:
                self.remove_instance_endpoint("decode", decode_instance)
                raise http_exc
            response = StreamingResponse(content=generator)
            return response
        except Exception:
            exc_info = sys.exc_info()
            error_messages = [str(e) for e in exc_info if e]
            print("Error occurred in disagg proxy server")
            print(error_messages)
            return StreamingResponse(
                content=iter(error_messages), media_type="text/event-stream"
            )

    def remove_instance_endpoint(self, instance_type, instance):
        if instance_type == "decode" and instance in self.decode_instances:
            self.decode_instances.remove(instance)
            self.decode_cycler = itertools.cycle(self.decode_instances)
        if instance_type == "prefill" and instance in self.prefill_instances:
            self.prefill_instances.remove(instance)
            self.prefill_cycler = itertools.cycle(self.prefill_instances)


class RoundRobinSchedulingPolicy(SchedulingPolicy):
    def __init__(self):
        super().__init__()

    def schedule(self, cycler: itertools.cycle) -> str:
        return next(cycler)


class ProxyServer:
    def __init__(
        self,
        args: argparse.Namespace,
        scheduling_policy: SchedulingPolicy | None = None,
        create_completion: Callable[[Request], StreamingResponse] | None = None,
        create_chat_completion: Callable[[Request], StreamingResponse] | None = None,
    ):
        self.validate_parsed_serve_args(args)
        self.port = args.port
        self.proxy_instance = Proxy(
            prefill_instances=[] if args.prefill is None else args.prefill,
            decode_instances=[] if args.decode is None else args.decode,
            model=args.model,
            scheduling_policy=(
                scheduling_policy
                if scheduling_policy is not None
                else RoundRobinSchedulingPolicy()
            ),
            custom_create_completion=create_completion,
            custom_create_chat_completion=create_chat_completion,
        )

    def validate_parsed_serve_args(self, args: argparse.Namespace):
        if not args.prefill:
            raise ValueError("Please specify at least one prefill node.")
        if not args.decode:
            raise ValueError("Please specify at least one decode node.")
        self.validate_instances(args.prefill)
        self.validate_instances(args.decode)
        self.verify_model_config(args.prefill, args.model)
        self.verify_model_config(args.decode, args.model)

    def validate_instances(self, instances: list):
        for instance in instances:
            if len(instance.split(":")) != 2:
                raise ValueError(f"Invalid instance format: {instance}")
            host, port = instance.split(":")
            try:
                if host != "localhost":
                    ipaddress.ip_address(host)
                port = int(port)
                if not (0 < port < 65536):
                    raise ValueError(f"Invalid port number in instance: {instance}")
            except Exception as e:
                raise ValueError(f"Invalid instance {instance}: {str(e)}") from e

    def verify_model_config(self, instances: list, model: str) -> None:
        model_suffix = model.split("/")[-1]
        for instance in instances:
            try:
                response = requests.get(f"http://{instance}/v1/models")
                if response.status_code == 200:
                    model_cur = response.json()["data"][0]["id"]
                    model_cur_suffix = model_cur.split("/")[-1]
                    if model_cur_suffix != model_suffix:
                        raise ValueError(
                            f"{instance} serves a different model: "
                            f"{model_cur} != {model}"
                        )
                else:
                    raise ValueError(f"Cannot get model id from {instance}!")
            except requests.RequestException as e:
                raise ValueError(
                    f"Error communicating with {instance}: {str(e)}"
                ) from e

    def run_server(self):
        app = FastAPI()
        app.include_router(self.proxy_instance.router)
        config = uvicorn.Config(app, port=self.port, loop="uvloop")
        server = uvicorn.Server(config)
        server.run()


def parse_args():
    # Todo: allow more config
    parser = argparse.ArgumentParser("vLLM disaggregated proxy server.")
    parser.add_argument("--model", "-m", type=str, required=True, help="Model name")

    parser.add_argument(
        "--prefill",
        "-p",
        type=str,
        nargs="+",
        help="List of prefill node URLs (host:port)",
    )

    parser.add_argument(
        "--decode",
        "-d",
        type=str,
        nargs="+",
        help="List of decode node URLs (host:port)",
    )

    parser.add_argument(
        "--port",
        type=int,
        default=8000,
        help="Server port number",
    )
    return parser.parse_args()


if __name__ == "__main__":
    args = parse_args()
    proxy_server = ProxyServer(args=args)
    proxy_server.run_server()

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""Disaggregated multimodal serving: render → generate round-trip.

Demonstrates the two-phase disaggregated flow:
  1. /v1/chat/completions/render  – preprocesses a multimodal chat request
     into token IDs and serialized tensor features.
  2. /inference/v1/generate       – runs inference on the preprocessed tokens.

The render response is passed *directly* to generate with only
``sampling_params`` added, showing that the two endpoints compose with
zero client-side transformation.

Launch the server first:

    vllm serve Qwen/Qwen3-VL-2B-Instruct \
        --dtype bfloat16 --max-model-len 4096 --enforce-eager

Then run this script:

    python example_mm_serve.py
"""

import io

import pybase64 as base64
import requests
from PIL import Image
from transformers import AutoTokenizer

BASE_URL = "http://localhost:8000"
MODEL_NAME = "Qwen/Qwen3-VL-2B-Instruct"


def make_data_url(image: Image.Image) -> str:
    """Encode a PIL image as a base64 data URL."""
    buf = io.BytesIO()
    image.save(buf, format="PNG")
    b64 = base64.b64encode(buf.getvalue()).decode()
    return f"data:image/png;base64,{b64}"


def main():
    # -- Step 1: Create a test image (solid red) -------------------------
    image = Image.new("RGB", (224, 224), color=(255, 0, 0))
    data_url = make_data_url(image)
    print("Created 224x224 red test image")

    # -- Step 2: Render (preprocess) -------------------------------------
    render_payload = {
        "model": MODEL_NAME,
        "messages": [
            {
                "role": "user",
                "content": [
                    {"type": "image_url", "image_url": {"url": data_url}},
                    {
                        "type": "text",
                        "text": "What color is this image? Answer in one word.",
                    },
                ],
            }
        ],
    }

    print("\n--- Render ---")
    render_resp = requests.post(
        f"{BASE_URL}/v1/chat/completions/render", json=render_payload
    )
    render_resp.raise_for_status()
    render_data = render_resp.json()

    print(f"Response keys: {list(render_data.keys())}")
    print(f"Number of token_ids: {len(render_data['token_ids'])}")

    features = render_data.get("features")
    if features and features.get("kwargs_data"):
        print(f"kwargs_data modalities: {list(features['kwargs_data'].keys())}")
        for modality, items in features["kwargs_data"].items():
            print(
                f"  {modality}: {len(items)} item(s), "
                f"first item type: {type(items[0])} length: {len(items[0])}"
                if items
                else "First item: (empty)"
            )
    else:
        print("WARNING: no kwargs_data in render response")

    # -- Step 3: Generate (inference) ------------------------------------
    # Pass the render output directly — only add sampling_params.
    generate_payload = render_data
    generate_payload["sampling_params"] = {
        "max_tokens": 20,
        "temperature": 0.0,
    }

    print("\n--- Generate ---")
    gen_resp = requests.post(f"{BASE_URL}/inference/v1/generate", json=generate_payload)
    gen_resp.raise_for_status()
    gen_data = gen_resp.json()

    # -- Step 4: Decode & print ------------------------------------------
    output_ids = gen_data["choices"][0]["token_ids"]
    tokenizer = AutoTokenizer.from_pretrained(MODEL_NAME)
    text = tokenizer.decode(output_ids, skip_special_tokens=True)

    print(f"Output token count: {len(output_ids)}")
    print(f"Generated text: {text!r}")

    if "red" in text.lower():
        print("\nModel correctly identified the red image.")
    else:
        print(f"\nWARNING: Expected 'red' in output, got: {text!r}")


if __name__ == "__main__":
    main()

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
import asyncio
import copy
import logging
import os
import socket
import threading
import uuid

import aiohttp
import msgpack
import zmq
from quart import Quart, Request, make_response, request

from vllm.distributed.kv_transfer.kv_connector.v1.moriio.moriio_common import (
    MoRIIOConstants,
)

logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
prefill_instances: list[dict] = []
decode_instances: list[dict] = []
request_nums = 0
app = Quart(__name__)


TRANSFER_TYPE = None


_list_lock = threading.RLock()


def _listen_for_register(hostname, port):
    context = zmq.Context()
    router_socket = context.socket(zmq.ROUTER)
    router_socket.bind(f"tcp://{hostname}:{port}")
    poller = zmq.Poller()
    poller.register(router_socket, zmq.POLLIN)
    global prefill_instances
    global decode_instances

    while True:
        socks = dict(poller.poll())
        if router_socket in socks:
            remote_addr, msg = router_socket.recv_multipart()
            data = msgpack.loads(msg)
            if data.get("type") == "HELLO":
                pass
            elif data.get("type") in ("P", "D"):
                role = data["type"]
                required_keys = {
                    "http_address",
                    "zmq_address",
                    "dp_size",
                    "tp_size",
                    "transfer_mode",
                }
                missing = required_keys - data.keys()
                if missing:
                    logger.error(
                        "Registration message missing required keys %s; skipping",
                        missing,
                    )
                    continue
                # Derive request_address from http_address
                # api path suffix is appended at request time
                instance = {
                    "role": role,
                    "request_address": f"http://{data['http_address']}/v1",
                    "http_address": data["http_address"],
                    "zmq_address": data["zmq_address"],
                    "dp_size": data["dp_size"],
                    "tp_size": data["tp_size"],
                    "transfer_mode": data["transfer_mode"],
                }
                # zmq_address format: "host:IP,handshake:PORT,notify:PORT"
                # Stored verbatim; embedded into the request_id by handle_request.

                global TRANSFER_TYPE
                transfer_mode = instance["transfer_mode"]
                target_list = prefill_instances if role == "P" else decode_instances
                with _list_lock:
                    if TRANSFER_TYPE is None:
                        TRANSFER_TYPE = transfer_mode
                        logger.info("SET TRANSFER TYPE TO %s", TRANSFER_TYPE)
                    elif transfer_mode != TRANSFER_TYPE:
                        logger.error(
                            "Mismatched transfer mode: expected %s, got %s;"
                            " skipping registration of %s",
                            TRANSFER_TYPE,
                            transfer_mode,
                            data["http_address"],
                        )
                        continue
                    existing_idx = next(
                        (
                            idx
                            for idx, i in enumerate(target_list)
                            if i.get("http_address") == data["http_address"]
                        ),
                        None,
                    )
                    if existing_idx is not None:
                        target_list[existing_idx] = instance
                        logger.info(
                            "Updated existing %s instance: %s",
                            "Prefill" if role == "P" else "Decode",
                            instance,
                        )
                    else:
                        target_list.append(instance)
                        logger.info(
                            "Registered %s instance: %s",
                            "Prefill" if role == "P" else "Decode",
                            instance,
                        )
            else:
                logger.warning(
                    "Received message with unrecognized type %r; ignoring",
                    data.get("type"),
                )


def start_service_discovery(hostname, port):
    if not hostname:
        hostname = socket.gethostname()
    if port == 0:
        raise ValueError("Port cannot be 0")

    _listener_thread = threading.Thread(
        target=_listen_for_register, args=(hostname, port), daemon=True
    )
    _listener_thread.start()
    return _listener_thread


async def send_request_to_prefill(
    endpoint, req_data, request_id, selected_prefill_dp_rank
):
    req_data_copy = req_data

    req_data_copy["kv_transfer_params"].update(
        {
            "do_remote_decode": True,
            "do_remote_prefill": False,
            "remote_engine_id": None,
            "remote_block_ids": None,
        }
    )
    req_data_copy["stream"] = False
    req_data_copy["max_tokens"] = 1
    if "max_completion_tokens" in req_data_copy:
        req_data_copy["max_completion_tokens"] = 1
    if "stream_options" in req_data_copy:
        del req_data_copy["stream_options"]
    async with aiohttp.ClientSession(
        timeout=aiohttp.ClientTimeout(total=6 * 6000 * 6000)
    ) as session:
        headers = {
            "Authorization": f"Bearer {os.environ.get('OPENAI_API_KEY')}",
            "X-Request-Id": request_id,
        }
        if selected_prefill_dp_rank is not None:
            headers["X-data-parallel-rank"] = str(selected_prefill_dp_rank)
        async with session.post(
            url=endpoint, json=req_data_copy, headers=headers
        ) as response:
            if response.status == 200:
                return await response.json()

            else:
                error_message = (
                    f"send_request_to_prefill response ={response},"
                    f"reason={response.reason}, status={response.status},"
                    f"method={response.method}, url={response.url},"
                    f"real_url={response.real_url}"
                )
                raise RuntimeError(error_message)


async def start_decode_request(endpoint, req_data, request_id):
    session = aiohttp.ClientSession(
        timeout=aiohttp.ClientTimeout(total=6 * 6000 * 6000)
    )
    headers = {
        "Authorization": f"Bearer {os.environ.get('OPENAI_API_KEY')}",
        "X-Request-Id": request_id,
    }
    response = await session.post(url=endpoint, json=req_data, headers=headers)
    return session, response


async def stream_decode_response(session, response, request_id):
    try:
        if response.status == 200:
            async for chunk_bytes in response.content.iter_chunked(1024):
                yield chunk_bytes
        else:
            error_message = (
                f"stream_decode_response response ={response},"
                f"reason={response.reason}, status={response.status},"
                f"method={response.method}, url={response.url},"
                f"real_url={response.real_url}"
            )
            raise RuntimeError(error_message)
    finally:
        await session.close()


def example_round_robin_dp_loader(request_number, dp_size):
    return request_nums % dp_size


@app.route("/v1/completions", methods=["POST"])
async def handle_completions_request():
    return await handle_request("/completions", request)


@app.route("/v1/chat/completions", methods=["POST"])
async def handle_chat_completions_request():
    return await handle_request("/chat/completions", request)


async def handle_request(api: str, request: Request):
    try:
        with _list_lock:
            global request_nums
            request_nums += 1

        req_data = await request.get_json()

        prefill_instance_endpoint = None
        decode_instance_endpoint = None
        error_msg = (
            "Service Unavailable: No prefill or decode instances are registered."
        )
        if not prefill_instances or not decode_instances:
            return await make_response(
                (
                    error_msg,
                    503,
                )
            )
        pid = request_nums % len(prefill_instances)
        did = request_nums % len(decode_instances)
        prefill_instance_endpoint = prefill_instances[pid]
        decode_instance_endpoint = decode_instances[did]

        selected_prefill_dp_rank = None
        if prefill_instance_endpoint["dp_size"] > 1:
            selected_prefill_dp_rank = example_round_robin_dp_loader(
                request_nums // len(prefill_instance_endpoint),
                prefill_instance_endpoint["dp_size"],
            )

        # Embed both zmq_addresses in the request_id so the connector can parse
        # the peer's host/ports from it, similar to P2P-NCCL
        uid = str(uuid.uuid4()).replace("-", "")
        request_id = (
            f"___prefill_addr_{prefill_instance_endpoint['zmq_address']}"
            f"___decode_addr_{decode_instance_endpoint['zmq_address']}"
            f"_{uid}"
        )

        transfer_id = f"{MoRIIOConstants.TRANSFER_PREFIX}-{str(uuid.uuid4())}"

        req_data_to_prefill = copy.deepcopy(req_data)
        req_data_to_prefill["kv_transfer_params"] = {}
        req_data["kv_transfer_params"] = {}
        req_data_to_prefill["kv_transfer_params"]["remote_dp_size"] = (
            decode_instance_endpoint["dp_size"]
        )
        req_data_to_prefill["kv_transfer_params"]["remote_tp_size"] = (
            decode_instance_endpoint["tp_size"]
        )
        req_data_to_prefill["kv_transfer_params"]["transfer_id"] = transfer_id

        prefill_request_url = prefill_instance_endpoint["request_address"] + api
        send_prefill_task = asyncio.create_task(
            send_request_to_prefill(
                prefill_request_url,
                req_data_to_prefill,
                request_id,
                selected_prefill_dp_rank,
            )
        )

        req_data["max_tokens"] -= 1

        req_data["kv_transfer_params"] = {
            "do_remote_decode": False,
            "do_remote_prefill": True,
            "remote_engine_id": None,
            "remote_block_ids": None,
            "transfer_id": transfer_id,
        }
        if TRANSFER_TYPE == "READ":
            # In read mode, prefill and decode are executed serially.
            prefill_response = await send_prefill_task
            prefill_kv = prefill_response["kv_transfer_params"]
            req_data["kv_transfer_params"]["remote_engine_id"] = prefill_kv[
                "remote_engine_id"
            ]
            req_data["kv_transfer_params"]["remote_block_ids"] = prefill_kv[
                "remote_block_ids"
            ]
            req_data["kv_transfer_params"]["transfer_id"] = prefill_kv["transfer_id"]

        req_data["kv_transfer_params"]["remote_dp_size"] = prefill_instance_endpoint[
            "dp_size"
        ]
        req_data["kv_transfer_params"]["remote_tp_size"] = prefill_instance_endpoint[
            "tp_size"
        ]

        if selected_prefill_dp_rank is not None:
            req_data["kv_transfer_params"]["remote_dp_rank"] = selected_prefill_dp_rank

        decode_request_url = decode_instance_endpoint["request_address"] + api
        decode_request_task = asyncio.create_task(
            start_decode_request(decode_request_url, req_data, request_id)
        )

        session, decode_response = await decode_request_task
        stream_generator = stream_decode_response(session, decode_response, request_id)
        response = await make_response(stream_generator)
        return response
    except Exception as e:
        logger.exception("An error occurred while handling the request: %s", e)
        return await make_response(
            (
                f"Internal Server Error: {e!s}",
                500,
            )
        )


if __name__ == "__main__":
    t = start_service_discovery("0.0.0.0", 36367)
    app.debug = True
    app.config["BODY_TIMEOUT"] = 360000
    app.config["RESPONSE_TIMEOUT"] = 360000

    app.run(host="0.0.0.0", port=10001)
    t.join()