# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
import asyncio
import contextlib
import queue
import sys
import uuid
import weakref
from abc import ABC, abstractmethod
from collections import defaultdict, deque
from collections.abc import Awaitable, Sequence
from concurrent.futures import Future
from dataclasses import dataclass
from threading import Thread
from typing import Any, Callable, Optional, TypeVar, Union

import msgspec.msgpack
import zmq
import zmq.asyncio

from vllm.config import VllmConfig
from vllm.logger import init_logger
from vllm.lora.request import LoRARequest
from vllm.utils import get_open_port, get_open_zmq_inproc_path, make_zmq_socket
from vllm.v1.engine import (EngineCoreOutputs, EngineCoreRequest,
                            EngineCoreRequestType,
                            ReconfigureDistributedRequest, ReconfigureRankType,
                            UtilityOutput)
from vllm.v1.engine.coordinator import DPCoordinator
from vllm.v1.engine.core import EngineCore, EngineCoreProc
from vllm.v1.engine.exceptions import EngineDeadError
from vllm.v1.engine.utils import (CoreEngineActorManager,
                                  CoreEngineProcManager, launch_core_engines)
from vllm.v1.executor.abstract import Executor
from vllm.v1.serial_utils import MsgpackDecoder, MsgpackEncoder, bytestr

logger = init_logger(__name__)

AnyFuture = Union[asyncio.Future[Any], Future[Any]]

_R = TypeVar('_R')  # Return type for collective_rpc

EngineIdentity = bytes


class EngineCoreClient(ABC):
    """
    EngineCoreClient: subclasses handle different methods for pushing 
        and pulling from the EngineCore for asyncio / multiprocessing.

    Subclasses:
    * InprocClient: In process EngineCore (for V0-style LLMEngine use)
    * SyncMPClient: ZMQ + background proc EngineCore (for LLM)
    * AsyncMPClient: ZMQ + background proc EngineCore w/ asyncio (for AsyncLLM)
    """

    @staticmethod
    def make_client(
        multiprocess_mode: bool,
        asyncio_mode: bool,
        vllm_config: VllmConfig,
        executor_class: type[Executor],
        log_stats: bool,
    ) -> "EngineCoreClient":

        # TODO: support this for debugging purposes.
        if asyncio_mode and not multiprocess_mode:
            raise NotImplementedError(
                "Running EngineCore in asyncio without multiprocessing "
                "is not currently supported.")

        if multiprocess_mode and asyncio_mode:
            return EngineCoreClient.make_async_mp_client(
                vllm_config, executor_class, log_stats)

        if multiprocess_mode and not asyncio_mode:
            return SyncMPClient(vllm_config, executor_class, log_stats)

        return InprocClient(vllm_config, executor_class, log_stats)

    @staticmethod
    def make_async_mp_client(
        vllm_config: VllmConfig,
        executor_class: type[Executor],
        log_stats: bool,
        client_addresses: Optional[dict[str, str]] = None,
        client_index: int = 0,
    ) -> "MPClient":
        parallel_config = vllm_config.parallel_config
        client_args = (vllm_config, executor_class, log_stats,
                       client_addresses, client_index)
        if parallel_config.data_parallel_size > 1:
            if parallel_config.data_parallel_external_lb:
                # External load balancer - client per DP rank.
                return DPAsyncMPClient(*client_args)
            # Internal load balancer - client balances to all DP ranks.
            return DPLBAsyncMPClient(*client_args)
        return AsyncMPClient(*client_args)

    @abstractmethod
    def shutdown(self):
        ...

    def get_output(self) -> EngineCoreOutputs:
        raise NotImplementedError

    def add_request(self, request: EngineCoreRequest) -> None:
        raise NotImplementedError

    def profile(self, is_start: bool = True) -> None:
        raise NotImplementedError

    def reset_mm_cache(self) -> None:
        raise NotImplementedError

    def reset_prefix_cache(self) -> None:
        raise NotImplementedError

    def sleep(self, level: int = 1) -> None:
        raise NotImplementedError

    def wake_up(self, tags: Optional[list[str]] = None) -> None:
        raise NotImplementedError

    def is_sleeping(self) -> bool:
        raise NotImplementedError

    def execute_dummy_batch(self) -> None:
        raise NotImplementedError

    async def execute_dummy_batch_async(self) -> None:
        raise NotImplementedError

    def abort_requests(self, request_ids: list[str]) -> None:
        raise NotImplementedError

    def add_lora(self, lora_request: LoRARequest) -> bool:
        raise NotImplementedError

    def remove_lora(self, lora_id: int) -> bool:
        raise NotImplementedError

    def list_loras(self) -> set[int]:
        raise NotImplementedError

    def pin_lora(self, lora_id: int) -> bool:
        raise NotImplementedError

    def save_sharded_state(self,
                           path: str,
                           pattern: Optional[str] = None,
                           max_size: Optional[int] = None) -> None:
        raise NotImplementedError

    def collective_rpc(self,
                       method: Union[str, Callable[..., _R]],
                       timeout: Optional[float] = None,
                       args: tuple = (),
                       kwargs: Optional[dict[str, Any]] = None) -> list[_R]:
        raise NotImplementedError

    def dp_engines_running(self) -> bool:
        """Returns True id data parallel engines are collectively in a
        running state."""
        raise NotImplementedError

    async def scale_elastic_ep(self, new_data_parallel_size: int) -> None:
        raise NotImplementedError

    async def get_output_async(self) -> EngineCoreOutputs:
        raise NotImplementedError

    async def add_request_async(self, request: EngineCoreRequest) -> None:
        raise NotImplementedError

    async def profile_async(self, is_start: bool = True) -> None:
        raise NotImplementedError

    async def reset_mm_cache_async(self) -> None:
        raise NotImplementedError

    async def reset_prefix_cache_async(self) -> None:
        raise NotImplementedError

    async def sleep_async(self, level: int = 1) -> None:
        raise NotImplementedError

    async def wake_up_async(self, tags: Optional[list[str]] = None) -> None:
        raise NotImplementedError

    async def is_sleeping_async(self) -> bool:
        raise NotImplementedError

    async def abort_requests_async(self, request_ids: list[str]) -> None:
        raise NotImplementedError

    async def add_lora_async(self, lora_request: LoRARequest) -> bool:
        raise NotImplementedError

    async def remove_lora_async(self, lora_id: int) -> bool:
        raise NotImplementedError

    async def list_loras_async(self) -> set[int]:
        raise NotImplementedError

    async def pin_lora_async(self, lora_id: int) -> bool:
        raise NotImplementedError

    async def save_sharded_state_async(self,
                                       path: str,
                                       pattern: Optional[str] = None,
                                       max_size: Optional[int] = None) -> None:
        raise NotImplementedError

    async def collective_rpc_async(
            self,
            method: Union[str, Callable[..., _R]],
            timeout: Optional[float] = None,
            args: tuple = (),
            kwargs: Optional[dict[str, Any]] = None) -> list[_R]:
        raise NotImplementedError


class InprocClient(EngineCoreClient):
    """
    InprocClient: client for in-process EngineCore. Intended 
    for use in LLMEngine for V0-style add_request() and step()
        EngineCore setup in this process (no busy loop).

        * pushes EngineCoreRequest directly into the EngineCore
        * pulls EngineCoreOutputs by stepping the EngineCore
    """

    def __init__(self, *args, **kwargs):
        self.engine_core = EngineCore(*args, **kwargs)

    def get_output(self) -> EngineCoreOutputs:
        outputs, _ = self.engine_core.step()
        return outputs.get(0) or EngineCoreOutputs()

    def add_request(self, request: EngineCoreRequest) -> None:
        self.engine_core.add_request(request)

    def abort_requests(self, request_ids: list[str]) -> None:
        if len(request_ids) > 0:
            self.engine_core.abort_requests(request_ids)

    def shutdown(self) -> None:
        self.engine_core.shutdown()

    def profile(self, is_start: bool = True) -> None:
        self.engine_core.profile(is_start)

    def reset_mm_cache(self) -> None:
        self.engine_core.reset_mm_cache()

    def reset_prefix_cache(self) -> None:
        self.engine_core.reset_prefix_cache()

    def sleep(self, level: int = 1) -> None:
        self.engine_core.sleep(level)

    def wake_up(self, tags: Optional[list[str]] = None) -> None:
        self.engine_core.wake_up(tags)

    def is_sleeping(self) -> bool:
        return self.engine_core.is_sleeping()

    def execute_dummy_batch(self) -> None:
        self.engine_core.execute_dummy_batch()

    def add_lora(self, lora_request: LoRARequest) -> bool:
        return self.engine_core.add_lora(lora_request)

    def remove_lora(self, lora_id: int) -> bool:
        return self.engine_core.remove_lora(lora_id)

    def list_loras(self) -> set[int]:
        return self.engine_core.list_loras()

    def pin_lora(self, lora_id: int) -> bool:
        return self.engine_core.pin_lora(lora_id)

    def save_sharded_state(self,
                           path: str,
                           pattern: Optional[str] = None,
                           max_size: Optional[int] = None) -> None:
        self.engine_core.save_sharded_state(path, pattern, max_size)

    def collective_rpc(self,
                       method: Union[str, Callable[..., _R]],
                       timeout: Optional[float] = None,
                       args: tuple = (),
                       kwargs: Optional[dict[str, Any]] = None) -> list[_R]:
        return self.engine_core.collective_rpc(method, timeout, args, kwargs)

    def dp_engines_running(self) -> bool:
        return False


@dataclass
class BackgroundResources:
    """Used as a finalizer for clean shutdown, avoiding
    circular reference back to the client object."""

    ctx: Union[zmq.Context]
    # If CoreEngineProcManager, it manages local engines;
    # if CoreEngineActorManager, it manages all engines.
    engine_manager: Optional[Union[CoreEngineProcManager,
                                   CoreEngineActorManager]] = None
    coordinator: Optional[DPCoordinator] = None
    output_socket: Optional[Union[zmq.Socket, zmq.asyncio.Socket]] = None
    input_socket: Optional[Union[zmq.Socket, zmq.asyncio.Socket]] = None
    first_req_send_socket: Optional[zmq.asyncio.Socket] = None
    output_queue_task: Optional[asyncio.Task] = None
    stats_update_task: Optional[asyncio.Task] = None
    shutdown_path: Optional[str] = None

    # Set if any of the engines are dead. Here so that the output
    # processing threads can access it without holding a ref to the client.
    engine_dead: bool = False

    def __call__(self):
        """Clean up background resources."""

        self.engine_dead = True
        if self.engine_manager is not None:
            self.engine_manager.close()
        if self.coordinator is not None:
            self.coordinator.close()

        if self.output_queue_task is not None:
            self.output_queue_task.cancel()
        if self.stats_update_task is not None:
            self.stats_update_task.cancel()

        # ZMQ context termination can hang if the sockets
        # aren't explicitly closed first.
        for socket in (self.output_socket, self.input_socket,
                       self.first_req_send_socket):
            if socket is not None:
                socket.close(linger=0)

        if self.shutdown_path is not None:
            # We must ensure that the sync output socket is
            # closed cleanly in its own thread.
            with self.ctx.socket(zmq.PAIR) as shutdown_sender:
                shutdown_sender.connect(self.shutdown_path)
                # Send shutdown signal.
                shutdown_sender.send(b'')

    def validate_alive(self, frames: Sequence[zmq.Frame]):
        if len(frames) == 1 and (frames[0].buffer
                                 == EngineCoreProc.ENGINE_CORE_DEAD):
            self.engine_dead = True
            raise EngineDeadError()


class MPClient(EngineCoreClient):
    """
    MPClient: base client for multi-proc EngineCore.
        EngineCore runs in a background process busy loop, getting
        new EngineCoreRequests and returning EngineCoreOutputs

        * pushes EngineCoreRequests via input_socket
        * pulls EngineCoreOutputs via output_socket
    
        * AsyncMPClient subclass for AsyncLLM usage
        * SyncMPClient subclass for LLM usage
    """

    def __init__(
        self,
        asyncio_mode: bool,
        vllm_config: VllmConfig,
        executor_class: type[Executor],
        log_stats: bool,
        client_addresses: Optional[dict[str, str]] = None,
    ):
        self.vllm_config = vllm_config
        # Serialization setup.
        self.encoder = MsgpackEncoder()
        self.decoder = MsgpackDecoder(EngineCoreOutputs)

        # ZMQ setup.
        sync_ctx = zmq.Context(io_threads=2)
        self.ctx = zmq.asyncio.Context(sync_ctx) if asyncio_mode else sync_ctx

        # This will ensure resources created so far are closed
        # when the client is garbage collected, even if an
        # exception is raised mid-construction.
        self.resources = BackgroundResources(ctx=sync_ctx)
        self._finalizer = weakref.finalize(self, self.resources)
        success = False
        try:
            # State used for data parallel.
            self.engines_running = False

            self.stats_update_address: Optional[str] = None
            if client_addresses is not None:
                # Engines are managed externally to this client.
                input_address = client_addresses["input_address"]
                output_address = client_addresses["output_address"]
                self.stats_update_address = client_addresses.get(
                    "stats_update_address")
            else:
                # Engines are managed by this client.
                with launch_core_engines(vllm_config, executor_class,
                                         log_stats) as (engine_manager,
                                                        coordinator,
                                                        addresses):
                    self.resources.coordinator = coordinator
                    self.resources.engine_manager = engine_manager

                (input_address, ) = addresses.inputs
                (output_address, ) = addresses.outputs
                self.stats_update_address = (
                    addresses.frontend_stats_publish_address)
                if coordinator is not None:
                    assert self.stats_update_address == (
                        coordinator.get_stats_publish_address())

            # Create input and output sockets.
            self.input_socket = self.resources.input_socket = make_zmq_socket(
                self.ctx, input_address, zmq.ROUTER, bind=True)
            self.resources.output_socket = make_zmq_socket(
                self.ctx, output_address, zmq.PULL)

            parallel_config = vllm_config.parallel_config
            dp_size = parallel_config.data_parallel_size
            dp_rank = parallel_config.data_parallel_rank
            external_dp_lb = parallel_config.data_parallel_external_lb

            offline_mode = parallel_config.data_parallel_rank_local is not None
            engine_ranks = [dp_rank] if (offline_mode
                                         or external_dp_lb) else range(dp_size)
            assert parallel_config.data_parallel_size_local <= len(
                engine_ranks)

            # ZMQ identity of each engine that this client will talk to.
            self.core_engines: list[EngineIdentity] = [
                index.to_bytes(2, "little") for index in engine_ranks
            ]

            # Wait for ready messages from each engine on the input socket.
            identities = set(self.core_engines)
            sync_input_socket = zmq.Socket.shadow(self.input_socket)
            while identities:
                if not sync_input_socket.poll(timeout=600_000):
                    raise TimeoutError("Timed out waiting for engines to send"
                                       "initial message on input socket.")
                identity, _ = sync_input_socket.recv_multipart()
                identities.remove(identity)

            self.core_engine: EngineIdentity = self.core_engines[0]
            self.utility_results: dict[int, AnyFuture] = {}

            # Request objects which may contain pytorch-allocated tensors
            # that we need to keep references to until zmq is done with the
            # underlying data.
            self.pending_messages = deque[tuple[zmq.MessageTracker, Any]]()

            success = True
        finally:
            if not success:
                self._finalizer()

    def shutdown(self):
        # Terminate background resources.
        self._finalizer()

    def _format_exception(self, e: Exception) -> Exception:
        """If errored, use EngineDeadError so root cause is clear."""
        return EngineDeadError(
            suppress_context=True) if self.resources.engine_dead else e

    def ensure_alive(self):
        if self.resources.engine_dead:
            raise EngineDeadError()

    def add_pending_message(self, tracker: zmq.MessageTracker, msg: Any):
        if not tracker.done:
            self.pending_messages.appendleft((tracker, msg))

    def free_pending_messages(self):
        while self.pending_messages and self.pending_messages[-1][0].done:
            self.pending_messages.pop()

    def dp_engines_running(self) -> bool:
        return self.engines_running


def _process_utility_output(output: UtilityOutput,
                            utility_results: dict[int, AnyFuture]):
    """Set the result from a utility method in the waiting future"""
    future = utility_results.pop(output.call_id)
    if output.failure_message is not None:
        future.set_exception(Exception(output.failure_message))
    else:
        future.set_result(output.result)


class SyncMPClient(MPClient):
    """Synchronous client for multi-proc EngineCore."""

    def __init__(self, vllm_config: VllmConfig, executor_class: type[Executor],
                 log_stats: bool):
        super().__init__(
            asyncio_mode=False,
            vllm_config=vllm_config,
            executor_class=executor_class,
            log_stats=log_stats,
        )

        self.is_dp = self.vllm_config.parallel_config.data_parallel_size > 1
        self.outputs_queue = queue.Queue[Union[EngineCoreOutputs, Exception]]()

        # Ensure that the outputs socket processing thread does not have
        # a ref to the client which prevents gc.
        ctx = self.ctx
        out_socket = self.resources.output_socket
        decoder = self.decoder
        utility_results = self.utility_results
        outputs_queue = self.outputs_queue

        shutdown_path = get_open_zmq_inproc_path()
        resources = self.resources
        resources.shutdown_path = shutdown_path

        def process_outputs_socket():
            assert isinstance(out_socket, zmq.Socket)
            shutdown_socket = ctx.socket(zmq.PAIR)
            try:
                shutdown_socket.bind(shutdown_path)
                poller = zmq.Poller()
                poller.register(shutdown_socket, zmq.POLLIN)
                poller.register(out_socket, zmq.POLLIN)
                while True:
                    socks = poller.poll()
                    if not socks:
                        continue
                    if len(socks) == 2 or socks[0][0] == shutdown_socket:
                        # shutdown signal, exit thread.
                        break

                    frames = out_socket.recv_multipart(copy=False)
                    resources.validate_alive(frames)
                    outputs: EngineCoreOutputs = decoder.decode(frames)
                    if outputs.utility_output:
                        _process_utility_output(outputs.utility_output,
                                                utility_results)
                    else:
                        outputs_queue.put_nowait(outputs)
            except Exception as e:
                outputs_queue.put_nowait(e)
            finally:
                # Close sockets.
                shutdown_socket.close(linger=0)
                out_socket.close(linger=0)

        # Process outputs from engine in separate thread.
        self.output_queue_thread = Thread(target=process_outputs_socket,
                                          name="EngineCoreOutputQueueThread",
                                          daemon=True)
        self.output_queue_thread.start()

        # The thread takes on responsibility for closing the socket.
        self.resources.output_socket = None

    def get_output(self) -> EngineCoreOutputs:
        # If an exception arises in process_outputs_socket task,
        # it is forwarded to the outputs_queue so we can raise it
        # from this (run_output_handler) task to shut down the server.
        outputs = self.outputs_queue.get()
        if isinstance(outputs, Exception):
            raise self._format_exception(outputs) from None
        if outputs.wave_complete is not None:
            self.engines_running = False
        return outputs

    def _send_input(self, request_type: EngineCoreRequestType, request: Any):
        self.ensure_alive()
        self.free_pending_messages()
        # (Identity, RequestType, SerializedRequest)
        msg = (self.core_engine, request_type.value,
               *self.encoder.encode(request))

        if len(msg) <= 3:
            # No auxiliary buffers => no tensor backing buffers in request.
            self.input_socket.send_multipart(msg, copy=False)
            return

        tracker = self.input_socket.send_multipart(msg, copy=False, track=True)
        self.add_pending_message(tracker, request)

    def call_utility(self, method: str, *args) -> Any:
        call_id = uuid.uuid1().int >> 64
        future: Future[Any] = Future()
        self.utility_results[call_id] = future
        self._send_input(EngineCoreRequestType.UTILITY,
                         (0, call_id, method, args))

        return future.result()

    def add_request(self, request: EngineCoreRequest) -> None:
        if self.is_dp:
            self.engines_running = True
        self._send_input(EngineCoreRequestType.ADD, request)

    def abort_requests(self, request_ids: list[str]) -> None:
        if request_ids and not self.resources.engine_dead:
            self._send_input(EngineCoreRequestType.ABORT, request_ids)

    def profile(self, is_start: bool = True) -> None:
        self.call_utility("profile", is_start)

    def reset_mm_cache(self) -> None:
        self.call_utility("reset_mm_cache")

    def reset_prefix_cache(self) -> None:
        self.call_utility("reset_prefix_cache")

    def add_lora(self, lora_request: LoRARequest) -> bool:
        return self.call_utility("add_lora", lora_request)

    def remove_lora(self, lora_id: int) -> bool:
        return self.call_utility("remove_lora", lora_id)

    def list_loras(self) -> set[int]:
        return self.call_utility("list_loras")

    def pin_lora(self, lora_id: int) -> bool:
        return self.call_utility("pin_lora", lora_id)

    def sleep(self, level: int = 1) -> None:
        self.call_utility("sleep", level)

    def wake_up(self, tags: Optional[list[str]] = None) -> None:
        self.call_utility("wake_up", tags)

    def is_sleeping(self) -> bool:
        return self.call_utility("is_sleeping")

    def execute_dummy_batch(self) -> None:
        self.call_utility("execute_dummy_batch")

    def collective_rpc(self,
                       method: Union[str, Callable[..., _R]],
                       timeout: Optional[float] = None,
                       args: tuple = (),
                       kwargs: Optional[dict[str, Any]] = None) -> list[_R]:
        return self.call_utility("collective_rpc", method, timeout, args,
                                 kwargs)

    def save_sharded_state(self,
                           path: str,
                           pattern: Optional[str] = None,
                           max_size: Optional[int] = None) -> None:
        self.call_utility("save_sharded_state", path, pattern, max_size)


class AsyncMPClient(MPClient):
    """Asyncio-compatible client for multi-proc EngineCore."""

    def __init__(self,
                 vllm_config: VllmConfig,
                 executor_class: type[Executor],
                 log_stats: bool,
                 client_addresses: Optional[dict[str, str]] = None,
                 client_index: int = 0):
        super().__init__(
            asyncio_mode=True,
            vllm_config=vllm_config,
            executor_class=executor_class,
            log_stats=log_stats,
            client_addresses=client_addresses,
        )

        self.client_index = client_index
        self.outputs_queue = asyncio.Queue[Union[EngineCoreOutputs,
                                                 Exception]]()
        try:
            # If we are running in an asyncio event loop, start the queue task.
            # Otherwise, it will be started lazily. If it is not started here,
            # we could miss EXECUTOR_FAILED messages from engine core if they
            # occur prior to any requests being sent.
            asyncio.get_running_loop()
            self._ensure_output_queue_task()
        except RuntimeError:
            pass

    def _ensure_output_queue_task(self):
        resources = self.resources
        if resources.output_queue_task is not None:
            return

        # Perform IO in separate task to parallelize as much as possible.
        # Avoid task having direct reference back to the client.
        decoder = self.decoder
        utility_results = self.utility_results
        outputs_queue = self.outputs_queue
        output_handler: Optional[Callable[[AsyncMPClient, EngineCoreOutputs],
                                          Awaitable[None]]] = getattr(
                                              self.__class__,
                                              "process_engine_outputs", None)
        _self_ref = weakref.ref(self) if output_handler else None
        output_socket = resources.output_socket
        assert output_socket is not None

        async def process_outputs_socket():
            try:
                while True:
                    frames = await output_socket.recv_multipart(copy=False)
                    resources.validate_alive(frames)
                    outputs: EngineCoreOutputs = decoder.decode(frames)
                    if outputs.utility_output:
                        _process_utility_output(outputs.utility_output,
                                                utility_results)
                        continue

                    if output_handler is not None:
                        assert _self_ref is not None
                        _self = _self_ref()
                        if not _self:
                            # Client has been garbage collected, abort.
                            return
                        await output_handler(_self, outputs)

                    if outputs.outputs or outputs.scheduler_stats:
                        outputs_queue.put_nowait(outputs)
            except Exception as e:
                outputs_queue.put_nowait(e)

        resources.output_queue_task = asyncio.create_task(
            process_outputs_socket(), name="EngineCoreOutputQueueTask")

    async def get_output_async(self) -> EngineCoreOutputs:
        self._ensure_output_queue_task()
        # If an exception arises in process_outputs_socket task,
        # it is forwarded to the outputs_queue so we can raise it
        # from this (run_output_handler) task to shut down the server.
        assert self.outputs_queue is not None
        outputs = await self.outputs_queue.get()
        if isinstance(outputs, Exception):
            raise self._format_exception(outputs) from None
        return outputs

    def _send_input(self,
                    request_type: EngineCoreRequestType,
                    request: Any,
                    engine: Optional[EngineIdentity] = None) -> Awaitable[Any]:
        if engine is None:
            engine = self.core_engine

        message = (request_type.value, *self.encoder.encode(request))
        return self._send_input_message(message, engine, request)

    def _send_input_message(self, message: tuple[bytestr,
                                                 ...], engine: EngineIdentity,
                            objects: Any) -> Awaitable[Any]:
        """
        objects is a reference to retain until zmq is finished with the
        buffers, in case they were extracted from tensors in the request.
        """
        self.ensure_alive()
        self.free_pending_messages()

        msg = (engine, ) + message
        if not objects or len(msg) <= 3:
            # No auxiliary buffers => no tensor backing buffers in request.
            return self.input_socket.send_multipart(msg, copy=False)

        future: asyncio.Future[zmq.MessageTracker]
        future = self.input_socket.send_multipart(msg, copy=False, track=True)

        def add_pending(f: asyncio.Future[zmq.MessageTracker]):
            with contextlib.suppress(BaseException):
                self.add_pending_message(f.result(), objects)

        future.add_done_callback(add_pending)
        return future

    async def call_utility_async(self, method: str, *args) -> Any:
        return await self._call_utility_async(method,
                                              *args,
                                              engine=self.core_engine)

    async def _call_utility_async(self, method: str, *args,
                                  engine: EngineIdentity) -> Any:
        call_id = uuid.uuid1().int >> 64
        future = asyncio.get_running_loop().create_future()
        self.utility_results[call_id] = future
        message = (EngineCoreRequestType.UTILITY.value, *self.encoder.encode(
            (self.client_index, call_id, method, args)))
        await self._send_input_message(message, engine, args)
        self._ensure_output_queue_task()
        return await future

    async def add_request_async(self, request: EngineCoreRequest) -> None:
        request.client_index = self.client_index
        await self._send_input(EngineCoreRequestType.ADD, request)
        self._ensure_output_queue_task()

    async def abort_requests_async(self, request_ids: list[str]) -> None:
        if request_ids and not self.resources.engine_dead:
            await self._send_input(EngineCoreRequestType.ABORT, request_ids)

    async def profile_async(self, is_start: bool = True) -> None:
        await self.call_utility_async("profile", is_start)

    async def reset_mm_cache_async(self) -> None:
        await self.call_utility_async("reset_mm_cache")

    async def reset_prefix_cache_async(self) -> None:
        await self.call_utility_async("reset_prefix_cache")

    async def sleep_async(self, level: int = 1) -> None:
        await self.call_utility_async("sleep", level)

    async def wake_up_async(self, tags: Optional[list[str]] = None) -> None:
        await self.call_utility_async("wake_up", tags)

    async def is_sleeping_async(self) -> bool:
        return await self.call_utility_async("is_sleeping")

    async def execute_dummy_batch_async(self) -> None:
        await self.call_utility_async("execute_dummy_batch")

    async def add_lora_async(self, lora_request: LoRARequest) -> bool:
        return await self.call_utility_async("add_lora", lora_request)

    async def remove_lora_async(self, lora_id: int) -> bool:
        return await self.call_utility_async("remove_lora", lora_id)

    async def list_loras_async(self) -> set[int]:
        return await self.call_utility_async("list_loras")

    async def pin_lora_async(self, lora_id: int) -> bool:
        return await self.call_utility_async("pin_lora", lora_id)

    async def save_sharded_state_async(self,
                                       path: str,
                                       pattern: Optional[str] = None,
                                       max_size: Optional[int] = None) -> None:
        await self.call_utility_async("save_sharded_state", path, pattern,
                                      max_size)

    async def collective_rpc_async(
            self,
            method: Union[str, Callable[..., _R]],
            timeout: Optional[float] = None,
            args: tuple = (),
            kwargs: Optional[dict[str, Any]] = None) -> list[_R]:
        return await self.call_utility_async("collective_rpc", method, timeout,
                                             args, kwargs)


class DPAsyncMPClient(AsyncMPClient):
    """Asyncio-compatible client for multi-proc, multi-engine (data parallel)
    EngineCore. Assumes external load-balancing by default."""

    def __init__(self,
                 vllm_config: VllmConfig,
                 executor_class: type[Executor],
                 log_stats: bool,
                 client_addresses: Optional[dict[str, str]] = None,
                 client_index: int = 0):
        self.current_wave = 0

        super().__init__(vllm_config, executor_class, log_stats,
                         client_addresses, client_index)

        # List of [waiting, running] pair per engine.
        # Used only by DPLBAsyncMPClient subclass.
        self.lb_engines: list[list[int]] = []

        self.first_req_sock_addr = get_open_zmq_inproc_path()
        self.first_req_send_socket = self.resources.first_req_send_socket = (
            make_zmq_socket(self.ctx,
                            self.first_req_sock_addr,
                            zmq.PAIR,
                            bind=True))
        try:
            # If we are running in an asyncio event loop, start the stats task.
            # Otherwise, it will be started lazily.
            asyncio.get_running_loop()
            self._ensure_stats_update_task()
        except RuntimeError:
            pass

    def _ensure_stats_update_task(self):
        resources = self.resources
        if resources.stats_update_task is not None:
            return

        assert self.stats_update_address is not None

        async def run_engine_stats_update_task():
            with make_zmq_socket(self.ctx, self.stats_update_address,
                                 zmq.XSUB) as socket, make_zmq_socket(
                                     self.ctx,
                                     self.first_req_sock_addr,
                                     zmq.PAIR,
                                     bind=False) as first_req_rcv_socket:
                assert isinstance(socket, zmq.asyncio.Socket)
                assert isinstance(first_req_rcv_socket, zmq.asyncio.Socket)
                # Send subscription message.
                await socket.send(b'\x01')

                poller = zmq.asyncio.Poller()
                poller.register(socket, zmq.POLLIN)
                poller.register(first_req_rcv_socket, zmq.POLLIN)

                while True:
                    events = await poller.poll()
                    if not self.engines_running and len(events) == 2 or (
                            events[0][0] == first_req_rcv_socket):
                        # Check if this is a regular request notification or
                        # scale up notification
                        buf = first_req_rcv_socket.recv(
                            flags=zmq.NOBLOCK).result()

                        decoded = msgspec.msgpack.decode(buf)
                        if isinstance(
                                decoded,
                            (list, tuple)) and len(decoded) == 2 and decoded[
                                0] == "SCALE_ELASTIC_EP":
                            # Extract new engine count from the decoded message
                            new_engine_count = decoded[1]
                            # Send scale up notification to coordinator
                            scale_msg = msgspec.msgpack.encode(
                                ("SCALE_ELASTIC_EP", new_engine_count))
                            await socket.send(scale_msg)
                            continue

                        # we're sending a request while the engines are
                        # paused, so that it can wake the others up
                        # (to run dummy EP loop).
                        assert decoded[0] == "FIRST_REQ"
                        target_eng_index = decoded[1]
                        self.engines_running = True
                        msg = msgspec.msgpack.encode(
                            (target_eng_index, self.current_wave))
                        await socket.send(msg)

                    buf = None
                    while True:
                        # Drain all stats events (we only care about latest).
                        future: asyncio.Future[bytes] = socket.recv(
                            flags=zmq.NOBLOCK)
                        if isinstance(future.exception(), zmq.Again):
                            break
                        buf = future.result()
                    if buf is None:
                        continue

                    # Update local load-balancing state.
                    counts, wave, running = msgspec.msgpack.decode(buf)
                    self.current_wave = wave
                    self.engines_running = running
                    self.lb_engines = counts

        resources.stats_update_task = asyncio.create_task(
            run_engine_stats_update_task())

    async def add_request_async(self, request: EngineCoreRequest) -> None:
        self._ensure_stats_update_task()

        request.current_wave = self.current_wave
        request.client_index = self.client_index

        chosen_engine = self.get_core_engine_for_request(request)
        to_await = self._send_input(EngineCoreRequestType.ADD, request,
                                    chosen_engine)
        if not self.engines_running:
            # Notify coordinator that we're sending a request
            req_msg = msgspec.msgpack.encode(("FIRST_REQ", chosen_engine))
            await self.first_req_send_socket.send(req_msg)

        await to_await

        self._ensure_output_queue_task()

    def get_core_engine_for_request(self, request: EngineCoreRequest):
        return self.core_engine


class DPLBAsyncMPClient(DPAsyncMPClient):
    """Asyncio-compatible client for multi-proc, multi-engine (data parallel)
    EngineCore. Load-balances between multiple engine processes."""

    def __init__(self,
                 vllm_config: VllmConfig,
                 executor_class: type[Executor],
                 log_stats: bool,
                 client_addresses: Optional[dict[str, str]] = None,
                 client_index: int = 0):

        # To route aborts to the correct engine.
        self.reqs_in_flight: dict[str, EngineIdentity] = {}

        super().__init__(vllm_config, executor_class, log_stats,
                         client_addresses, client_index)

        assert len(self.core_engines) > 1

    def get_core_engine_for_request(
            self, request: EngineCoreRequest) -> EngineIdentity:
        # Engines are in rank order.
        if (eng_index := request.data_parallel_rank) is None:
            if not self.lb_engines:
                return self.core_engine
            # TODO use P2C alg for larger DP sizes
            num_engines = len(self.lb_engines)
            min_counts = [sys.maxsize, sys.maxsize]
            eng_index = 0
            for i in range(num_engines):
                # Start from client_index to help with balancing when engines
                # are empty.
                idx = (self.client_index + i) % num_engines
                counts = self.lb_engines[idx]
                if counts < min_counts:
                    min_counts = counts
                    eng_index = idx
            # Adjust local counts for better balancing between stats updates
            # from the coordinator (which happen every 100ms).
            if min_counts[0]:
                min_counts[0] += 1
            else:
                min_counts[1] += 1

        chosen_engine = self.core_engines[eng_index]
        # Record which engine is chosen for this request, to handle aborts.
        self.reqs_in_flight[request.request_id] = chosen_engine
        return chosen_engine

    async def call_utility_async(self, method: str, *args) -> Any:
        # Only the result from the first engine is returned.
        return (await asyncio.gather(*[
            self._call_utility_async(method, *args, engine=engine)
            for engine in self.core_engines
        ]))[0]

    @staticmethod
    async def process_engine_outputs(self: "DPLBAsyncMPClient",
                                     outputs: EngineCoreOutputs):
        if outputs.finished_requests and self.reqs_in_flight:
            for req_id in outputs.finished_requests:
                self.reqs_in_flight.pop(req_id, None)

    async def abort_requests_async(self, request_ids: list[str]) -> None:
        if not request_ids or self.resources.engine_dead:
            return

        if len(request_ids) == 1:
            # Fast-path common case.
            if engine := self.reqs_in_flight.get(request_ids[0]):
                await self._abort_requests(request_ids, engine)
            return

        by_engine = defaultdict[EngineIdentity, list[str]](list)
        for req_id in request_ids:
            if engine := self.reqs_in_flight.get(req_id):
                by_engine[engine].append(req_id)
        for engine, req_ids in by_engine.items():
            await self._abort_requests(req_ids, engine)

    async def _abort_requests(self, request_ids: list[str],
                              engine: EngineIdentity) -> None:
        await self._send_input(EngineCoreRequestType.ABORT, request_ids,
                               engine)

    async def _send_reconfig_message(
            self, reconfig_request: ReconfigureDistributedRequest,
            engine: EngineIdentity) -> asyncio.Future:
        """Send reconfiguration message and return the result future without
        waiting for completion."""
        call_id = uuid.uuid1().int >> 64
        future = asyncio.get_running_loop().create_future()
        self.utility_results[call_id] = future
        message = (EngineCoreRequestType.UTILITY.value, *self.encoder.encode(
            (self.client_index, call_id, "reinitialize_distributed",
             (reconfig_request, ))))
        await self._send_input_message(message, engine, reconfig_request)
        self._ensure_output_queue_task()
        return future

    async def scale_elastic_ep(self, new_data_parallel_size: int) -> None:
        """Scale elastic EP data parallel size"""
        cur_data_parallel_size = len(self.core_engines)

        assert new_data_parallel_size != cur_data_parallel_size, (
            f"new_data_parallel_size {new_data_parallel_size} must be "
            f"different from cur_data_parallel_size {cur_data_parallel_size}")

        assert self.vllm_config.parallel_config.data_parallel_backend == \
            "ray", ("Only ray DP backend supports scaling elastic EP")

        scale_up = new_data_parallel_size > cur_data_parallel_size

        if scale_up:
            await self._scale_up_elastic_ep(cur_data_parallel_size,
                                            new_data_parallel_size)
        else:
            await self._scale_down_elastic_ep(cur_data_parallel_size,
                                              new_data_parallel_size)

    async def _scale_up_elastic_ep(self, cur_data_parallel_size: int,
                                   new_data_parallel_size: int) -> None:
        """Scale up the data parallel size by creating new engine cores
        and reconfiguring existing ones."""
        cur_data_parallel_size = len(self.core_engines)

        # Phase 1: Send reconfigure messages to all existing engines and wait
        # for them to be sent
        reconfig_futures = []
        self.vllm_config.parallel_config.data_parallel_master_port = \
            get_open_port()
        for engine in self.core_engines:
            reconfig_request = ReconfigureDistributedRequest(
                new_data_parallel_size=new_data_parallel_size,
                new_data_parallel_rank=ReconfigureRankType.KEEP_CURRENT_RANK,
                new_data_parallel_rank_local=\
                ReconfigureRankType.KEEP_CURRENT_RANK,
                new_data_parallel_master_ip=self.vllm_config.parallel_config.
                data_parallel_master_ip,
                new_data_parallel_master_port=self.vllm_config.parallel_config.
                data_parallel_master_port)
            future = await self._send_reconfig_message(reconfig_request,
                                                       engine)
            reconfig_futures.append(future)

        logger.info("All reconfigure messages sent, starting engine creation")

        # Phase 2: Create new engines now that reconfig messages have been sent
        # self.resources.engine_manager is guaranteed to be
        # CoreEngineActorManager for RayDPClient
        assert isinstance(self.resources.engine_manager,
                          CoreEngineActorManager)
        self.resources.engine_manager.scale_up_elastic_ep(
            self.vllm_config, new_data_parallel_size)

        # Create new CoreEngine objects for the new engines
        new_engine_identities = set()
        for i in range(cur_data_parallel_size, new_data_parallel_size):
            new_engine = i.to_bytes(2, "little")
            self.core_engines.append(new_engine)
            new_engine_identities.add(new_engine)

        # Wait for ready messages from new engines on the input socket
        sync_input_socket = zmq.Socket.shadow(self.input_socket)
        while new_engine_identities:
            if not sync_input_socket.poll(timeout=600_000):
                raise TimeoutError(
                    "Timed out waiting for new engines to send initial "
                    "message on input socket.")
            identity, _ = sync_input_socket.recv_multipart()
            new_engine_identities.discard(identity)

        # Phase 3: Wait for all existing engines to complete reconfiguration
        logger.info("Waiting for existing engines to complete reconfiguration")
        await asyncio.gather(*reconfig_futures)

        # Notify coordinator about scale up through existing
        # stats_update_task connection
        self._ensure_stats_update_task()
        scale_up_marker = msgspec.msgpack.encode(
            ("SCALE_ELASTIC_EP", new_data_parallel_size))
        await self.first_req_send_socket.send(scale_up_marker)

        # Update the parallel config
        self.vllm_config.parallel_config.data_parallel_size = \
            new_data_parallel_size
        logger.info(
            "[Elastic EP] Scale up completed, new data parallel size: %s",
            new_data_parallel_size)

    async def _scale_down_elastic_ep(self, cur_data_parallel_size: int,
                                     new_data_parallel_size: int) -> None:
        """Scale down the data parallel size by shutting down and
        reconfiguring existing engine cores."""
        cur_data_parallel_size = len(self.core_engines)

        self.vllm_config.parallel_config.data_parallel_master_port = \
            get_open_port()

        reconfig_futures = []
        for cur_dp_rank, engine in enumerate(self.core_engines):
            reconfig_request = ReconfigureDistributedRequest(
                new_data_parallel_size=new_data_parallel_size,
                new_data_parallel_rank=ReconfigureRankType.KEEP_CURRENT_RANK,
                new_data_parallel_rank_local=\
                ReconfigureRankType.KEEP_CURRENT_RANK,
                new_data_parallel_master_ip=self.vllm_config.parallel_config.
                data_parallel_master_ip,
                new_data_parallel_master_port=self.vllm_config.parallel_config.
                data_parallel_master_port)
            if cur_dp_rank >= new_data_parallel_size:
                reconfig_request.new_data_parallel_rank = \
                ReconfigureRankType.SHUTDOWN_CURRENT_RANK
            future = await self._send_reconfig_message(reconfig_request,
                                                       engine)
            reconfig_futures.append(future)

        for _ in range(new_data_parallel_size, cur_data_parallel_size):
            self.core_engines.pop()

        await asyncio.gather(*reconfig_futures)

        assert isinstance(self.resources.engine_manager,
                          CoreEngineActorManager)
        self.resources.engine_manager.scale_down_elastic_ep(
            cur_data_parallel_size, new_data_parallel_size)

        self._ensure_stats_update_task()
        scale_down_marker = msgspec.msgpack.encode(
            ("SCALE_ELASTIC_EP", new_data_parallel_size))
        await self.first_req_send_socket.send(scale_down_marker)

        self.vllm_config.parallel_config.data_parallel_size = \
            new_data_parallel_size
        logger.info(
            "[Elastic EP] Scale down completed, new data parallel size: %s",
            new_data_parallel_size)
