vLLM/vllm/v1/engine/output_processor.py

# SPDX-License-Identifier: Apache-2.0

import asyncio
from dataclasses import dataclass
from typing import Dict, List, Optional

from vllm.outputs import RequestOutput
from vllm.transformers_utils.detokenizer_utils import AnyTokenizer
from vllm.transformers_utils.tokenizer_group import BaseTokenizerGroup
from vllm.v1.engine import EngineCoreOutput, EngineCoreRequest
from vllm.v1.engine.detokenizer import (DetokenizerOutput,
                                        IncrementalDetokenizer)
from vllm.v1.metrics.stats import IterationStats, RequestStateStats


@dataclass
class OutputProcessorOutput:

    request_outputs: List[RequestOutput]
    reqs_to_abort: List[str]
    iteration_stats: IterationStats


class RequestState:

    def __init__(
        self,
        request_id: str,
        prompt: Optional[str],
        prompt_token_ids: List[int],
        detokenizer: IncrementalDetokenizer,
        arrival_time: float,
        queue: Optional[asyncio.Queue[RequestOutput]],
    ):
        self.request_id = request_id
        self.prompt = prompt
        self.prompt_token_ids = prompt_token_ids
        self.prompt_len = len(prompt_token_ids)
        self.detokenizer = detokenizer
        self.is_prefilling = True
        self.queue = queue

        self.stats = RequestStateStats(last_token_time=arrival_time)

    @classmethod
    def from_new_request(
        cls,
        tokenizer: AnyTokenizer,
        request: EngineCoreRequest,
        queue: Optional[asyncio.Queue[RequestOutput]] = None,
    ) -> "RequestState":
        return cls(
            request_id=request.request_id,
            prompt=request.prompt,
            prompt_token_ids=request.prompt_token_ids,
            detokenizer=IncrementalDetokenizer.from_new_request(
                tokenizer=tokenizer,
                request=request,
            ),
            arrival_time=request.arrival_time,
            queue=queue,
        )


class OutputProcessor:
    """Process EngineCoreOutputs into RequestOutputs."""

    def __init__(
        self,
        tokenizer: BaseTokenizerGroup,
        log_stats: bool,
    ):
        self.log_stats = log_stats
        self.tokenizer = tokenizer
        self.request_states: Dict[str, RequestState] = {}

    def is_request_active(self, request_id: str) -> bool:
        return request_id in self.request_states

    def get_num_unfinished_requests(self):
        return len(self.request_states)

    def has_unfinished_requests(self) -> bool:
        return len(self.request_states) > 0

    def abort_requests(
        self,
        request_ids: List[str],
    ) -> None:
        for request_id in request_ids:
            self.request_states.pop(request_id, None)

    def add_request(
        self,
        request: EngineCoreRequest,
        queue: Optional[asyncio.Queue[RequestOutput]] = None,
    ) -> None:
        request_id = request.request_id
        if request_id in self.request_states:
            raise ValueError(f"Request id {request_id} already running.")

        self.request_states[request_id] = RequestState.from_new_request(
            tokenizer=self.tokenizer.get_lora_tokenizer(request.lora_request),
            request=request,
            queue=queue)

    def process_outputs(
        self,
        engine_core_outputs: List[EngineCoreOutput],
        iteration_stats: Optional[IterationStats] = None,
    ) -> OutputProcessorOutput:
        """
        Process the EngineCoreOutputs:
        1) Compute stats for logging
        2) Detokenize
        3) Create and handle RequestOutput objects:
            * If there is a queue (for usage with AsyncLLM), 
              put the RequestOutput objects into the queue for
              handling by the per-request generate() tasks.

            * If there is no queue (for usage with LLMEngine), 
              return a list of RequestOutput objects.

        ****************** NOTE FOR DEVELOPERS ******************

        VLLM V1 minimizes the number of python loops over the full
        batch to ensure system overheads are minimized. This is the 
        only function that should loop over EngineCoreOutputs.

        If you need to touch every element of the batch, implement a
        method called XXXClass.update_from_output() to be called
        within the loop below. For examples, see:
            * IterationStats.update_from_output()
            * Detokenizer.update_from_output()
        
        TODO(rob): add Protocol makes update_from_output explicit.
        
        **********************************************************
        """

        request_outputs: List[RequestOutput] = []
        reqs_to_abort: List[str] = []
        if not iteration_stats:
            iteration_stats = IterationStats(self.log_stats)
        for engine_core_output in engine_core_outputs:
            req_id = engine_core_output.request_id
            req_state = self.request_states.get(req_id)
            if req_state is None:
                # Ignore output for already-aborted request.
                continue

            # 1) Compute stats for this iteration.
            iteration_stats.update_from_output(engine_core_output,
                                               req_state.is_prefilling,
                                               req_state.prompt_len,
                                               req_state.stats)
            req_state.is_prefilling = False

            # 2) Detokenize the token ids into text.
            detokenizer_output = req_state.detokenizer.update_from_output(
                engine_core_output)

            # 3) Create and handle RequestOutput objects.
            if request_output := self._make_request_output(
                    req_state, detokenizer_output):
                if req_state.queue is not None:
                    # AsyncLLM: put into queue for handling by generate().
                    req_state.queue.put_nowait(request_output)
                else:
                    # LLMEngine: return list of RequestOutputs.
                    request_outputs.append(request_output)

                # Free completed requests.
                if request_output.finished:
                    self.request_states.pop(req_id)
                    if not engine_core_output.finished:
                        # If req not finished in EngineCore, but Detokenizer
                        # detected stop string, abort needed in EngineCore.
                        reqs_to_abort.append(req_id)

                    # Track per-request stats
                    iteration_stats.update_from_finished_request(
                        request_output, req_state.stats)

        return OutputProcessorOutput(
            request_outputs=request_outputs,
            reqs_to_abort=reqs_to_abort,
            iteration_stats=iteration_stats,
        )

    @staticmethod
    def _make_request_output(
        request_state: RequestState,
        detokenizer_output: Optional[DetokenizerOutput],
    ) -> Optional[RequestOutput]:

        if detokenizer_output is None:
            return None

        request_output = RequestOutput.new(
            request_state.request_id,
            request_state.prompt,
            request_state.prompt_token_ids,
            detokenizer_output.output_text,
            detokenizer_output.token_ids,
            detokenizer_output.finished,
        )
        if detokenizer_output.finished:
            completion_output = request_output.outputs[0]
            completion_output.finish_reason = detokenizer_output.finish_reason
            completion_output.stop_reason = detokenizer_output.stop_reason

        return request_output