distributed_gpu_executor.py

import asyncio
from abc import abstractmethod
from typing import Any, Awaitable, Dict, List, Optional, Set, Tuple, Union

from vllm.executor.executor_base import ExecutorAsyncBase
from vllm.executor.gpu_executor import GPUExecutor
from vllm.logger import init_logger
from vllm.lora.request import LoRARequest
from vllm.sequence import ExecuteModelRequest, SamplerOutput

logger = init_logger(__name__)


class DistributedGPUExecutor(GPUExecutor):
    """Abstract superclass of multi-GPU executor implementations."""

    def __init__(self, *args, **kwargs):
        # This is non-None when the execute model loop is running
        # in the parallel workers. It's a coroutine in the AsyncLLMEngine case.
        self.parallel_worker_tasks: Optional[Union[Any, Awaitable[Any]]] = None
        # Updated by implementations that require additional args to be passed
        # to the _run_workers execute_model call
        self.extra_execute_model_run_workers_kwargs: Dict[str, Any] = {}

        super().__init__(*args, **kwargs)

    def determine_num_available_blocks(self) -> Tuple[int, int]:
        """Determine the number of available KV blocks.

        This invokes `determine_num_available_blocks` on each worker and takes
        the min of the results, guaranteeing that the selected cache sizes are
        compatible with all workers.

        Returns:
            - tuple[num_gpu_blocks, num_cpu_blocks]
        """
        # Get the maximum number of blocks that can be allocated on GPU and CPU.
        num_blocks = self._run_workers("determine_num_available_blocks", )

        # Since we use a shared centralized controller, we take the minimum
        # number of blocks across all workers to make sure all the memory
        # operators can be applied to all workers.
        num_gpu_blocks = min(b[0] for b in num_blocks)
        num_cpu_blocks = min(b[1] for b in num_blocks)

        return num_gpu_blocks, num_cpu_blocks

    def initialize_cache(self, num_gpu_blocks: int,
                         num_cpu_blocks: int) -> None:
        """Initialize the KV cache in all workers.
        """

        # NOTE: We log here to avoid multiple logs when number of workers is
        # greater than one. We could log in the engine, but not all executors
        # have GPUs.
        logger.info("# GPU blocks: %d, # CPU blocks: %d", num_gpu_blocks,
                    num_cpu_blocks)

        self.cache_config.num_gpu_blocks = num_gpu_blocks
        self.cache_config.num_cpu_blocks = num_cpu_blocks

        self._run_workers("initialize_cache",
                          num_gpu_blocks=num_gpu_blocks,
                          num_cpu_blocks=num_cpu_blocks)

    def execute_model(
        self, execute_model_req: ExecuteModelRequest
    ) -> Optional[List[SamplerOutput]]:
        if self.parallel_worker_tasks is None:
            self.parallel_worker_tasks = self._run_workers(
                "start_worker_execution_loop",
                async_run_remote_workers_only=True,
                **self.extra_execute_model_run_workers_kwargs)

        # Only the driver worker returns the sampling results.
        return self._driver_execute_model(execute_model_req)

    def stop_remote_worker_execution_loop(self) -> None:
        if self.parallel_worker_tasks is None:
            return

        self._driver_execute_model(execute_model_req=None)
        parallel_worker_tasks = self.parallel_worker_tasks
        self.parallel_worker_tasks = None
        # Ensure that workers exit model loop cleanly
        # (this will raise otherwise)
        self._wait_for_tasks_completion(parallel_worker_tasks)

    def add_lora(self, lora_request: LoRARequest) -> bool:
        assert lora_request.lora_int_id > 0, "lora_id must be greater than 0."
        return self._run_workers(
            "add_lora",
            lora_request=lora_request,
        )

    def remove_lora(self, lora_id: int) -> bool:
        assert lora_id > 0, "lora_id must be greater than 0."
        return self._run_workers(
            "remove_lora",
            lora_id=lora_id,
        )

    def pin_lora(self, lora_id: int) -> bool:
        assert lora_id > 0, "lora_id must be greater than 0."
        return self._run_workers(
            "pin_lora",
            lora_id=lora_id,
        )

    def list_loras(self) -> Set[int]:
        return self._run_workers("list_loras")

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

    @abstractmethod
    def _driver_execute_model(
        self, execute_model_req: Optional[ExecuteModelRequest]
    ) -> Optional[List[SamplerOutput]]:
        """Run execute_model in the driver worker.

        Passing None will cause the driver to stop the model execution loop
        running in each of the remote workers. In this case, this method
        returns None. Otherwise, this method returns the model output.
        """
        raise NotImplementedError

    @abstractmethod
    def _run_workers(
        self,
        method: str,
        *args,
        async_run_remote_workers_only: bool = False,
        max_concurrent_workers: Optional[int] = None,
        **kwargs,
    ) -> Any:
        """Runs the given method on all workers.

        Args:
            async_run_remote_workers_only: If True the method will be run only
                in the remote workers, not the driver worker. It will also be
                run asynchronously and return a list of futures rather than
                blocking on the results.
        """
        raise NotImplementedError

    @abstractmethod
    def _wait_for_tasks_completion(self, parallel_worker_tasks: Any) -> None:
        """Wait for futures returned from _run_workers() with
        async_run_remote_workers_only to complete."""
        raise NotImplementedError


class DistributedGPUExecutorAsync(DistributedGPUExecutor, ExecutorAsyncBase):

    async def execute_model_async(
            self,
            execute_model_req: ExecuteModelRequest) -> List[SamplerOutput]:
        if self.parallel_worker_tasks is None:
            # Start model execution loop running in the parallel workers
            self.parallel_worker_tasks = asyncio.create_task(
                self._start_worker_execution_loop())

        # Only the driver worker returns the sampling results.
        return await self._driver_execute_model_async(execute_model_req)

    async def stop_remote_worker_execution_loop_async(self) -> None:
        if self.parallel_worker_tasks is None:
            return

        await self._driver_execute_model_async()
        parallel_worker_tasks = self.parallel_worker_tasks
        self.parallel_worker_tasks = None
        # Ensure that workers exit model loop cleanly
        # (this will raise otherwise)
        await parallel_worker_tasks

    @abstractmethod
    async def _driver_execute_model_async(
        self,
        execute_model_req: Optional[ExecuteModelRequest] = None
    ) -> List[SamplerOutput]:
        """Execute the model asynchronously in the driver worker.

        Passing None will cause the driver to stop the model execution
        loop running in each of the remote workers.
        """
        raise NotImplementedError

    @abstractmethod
    async def _start_worker_execution_loop(self):
        """Run execution loop on all workers. It guarantees all workers run
        the loop or None of them is running the loop. Loop can be stopped by
        `stop_remote_worker_execution_loop`.
        The API is idempotent (guarantee only 1 loop run at any moment)."""
        raise NotImplementedError