importing.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project

import os
import types
from importlib.util import find_spec

from vllm.logger import init_logger

logger = init_logger(__name__)

HAS_TRITON = (
    find_spec("triton") is not None
    or find_spec("pytorch-triton-xpu") is not None  # Not compatible
)
if HAS_TRITON:
    try:
        from triton.backends import backends

        # It's generally expected that x.driver exists and has
        # an is_active method.
        # The `x.driver and` check adds a small layer of safety.
        active_drivers = [
            x.driver for x in backends.values()
            if x.driver and x.driver.is_active()
        ]

        # Check if we're in a distributed environment where CUDA_VISIBLE_DEVICES
        # might be temporarily empty (e.g., Ray sets it to "" during actor init)
        cuda_visible_devices = os.environ.get("CUDA_VISIBLE_DEVICES")
        is_distributed_env = (cuda_visible_devices is not None
                              and len(cuda_visible_devices.strip()) == 0)

        # Apply lenient driver check for distributed environments
        if is_distributed_env and len(active_drivers) == 0:
            # Allow 0 drivers in distributed environments - they may become
            # active later when CUDA context is properly initialized
            logger.debug(
                "Triton found 0 active drivers in distributed environment. "
                "This is expected during initialization.")
        elif not is_distributed_env and len(active_drivers) != 1:
            # Strict check for non-distributed environments
            logger.info(
                "Triton is installed but %d active driver(s) found "
                "(expected 1). Disabling Triton to prevent runtime errors.",
                len(active_drivers))
            HAS_TRITON = False
    except ImportError:
        # This can occur if Triton is partially installed or triton.backends
        # is missing.
        logger.warning(
            "Triton is installed, but `triton.backends` could not be imported. "
            "Disabling Triton.")
        HAS_TRITON = False
    except Exception as e:
        # Catch any other unexpected errors during the check.
        logger.warning(
            "An unexpected error occurred while checking Triton active drivers:"
            " %s. Disabling Triton.", e)
        HAS_TRITON = False

if not HAS_TRITON:
    logger.info("Triton not installed or not compatible; certain GPU-related"
                " functions will not be available.")


class TritonPlaceholder(types.ModuleType):

    def __init__(self):
        super().__init__("triton")
        self.__version__ = "3.4.0"
        self.jit = self._dummy_decorator("jit")
        self.autotune = self._dummy_decorator("autotune")
        self.heuristics = self._dummy_decorator("heuristics")
        self.Config = self._dummy_decorator("Config")
        self.language = TritonLanguagePlaceholder()

    def _dummy_decorator(self, name):

        def decorator(*args, **kwargs):
            if args and callable(args[0]):
                return args[0]
            return lambda f: f

        return decorator


class TritonLanguagePlaceholder(types.ModuleType):

    def __init__(self):
        super().__init__("triton.language")
        self.constexpr = None
        self.dtype = None
        self.int64 = None
        self.int32 = None
        self.tensor = None