vllm.utils.system_utils ¶

def _add_prefix(file: TextIO, worker_name: str, pid: int) -> None:
    """Add colored prefix to file output for log decoration."""
    if envs.NO_COLOR:
        prefix = f"({worker_name} pid={pid}) "
    else:
        prefix = f"{CYAN}({worker_name} pid={pid}){RESET} "
    file_write = file.write

    def write_with_prefix(s: str):
        if not s:
            return
        if file.start_new_line:  # type: ignore[attr-defined]
            file_write(prefix)
        idx = 0
        while (next_idx := s.find("\n", idx)) != -1:
            next_idx += 1
            file_write(s[idx:next_idx])
            if next_idx == len(s):
                file.start_new_line = True  # type: ignore[attr-defined]
                return
            file_write(prefix)
            idx = next_idx
        file_write(s[idx:])
        file.start_new_line = False  # type: ignore[attr-defined]

    file.start_new_line = True  # type: ignore[attr-defined]
    file.write = write_with_prefix  # type: ignore[method-assign]

def _maybe_force_spawn():
    """Check if we need to force the use of the `spawn` multiprocessing start
    method.
    """
    if os.environ.get("VLLM_WORKER_MULTIPROC_METHOD") == "spawn":
        return

    reasons = []
    if is_in_ray_actor():
        # even if we choose to spawn, we need to pass the ray address
        # to the subprocess so that it knows how to connect to the ray cluster.
        # env vars are inherited by subprocesses, even if we use spawn.
        import ray

        os.environ["RAY_ADDRESS"] = ray.get_runtime_context().gcs_address
        reasons.append("In a Ray actor and can only be spawned")

    if cuda_is_initialized():
        reasons.append("CUDA is initialized")
    elif xpu_is_initialized():
        reasons.append("XPU is initialized")

    if in_wsl():
        reasons.append("WSL is detected and NVML is not compatible with fork")

    if reasons:
        logger.warning(
            "We must use the `spawn` multiprocessing start method. "
            "Overriding VLLM_WORKER_MULTIPROC_METHOD to 'spawn'. "
            "See https://docs.vllm.ai/en/latest/usage/"
            "troubleshooting.html#python-multiprocessing "
            "for more information. Reasons: %s",
            "; ".join(reasons),
        )
        os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"

def decorate_logs(process_name: str | None = None) -> None:
    """Decorate stdout/stderr with process name and PID prefix."""
    # Respect VLLM_CONFIGURE_LOGGING environment variable
    if not envs.VLLM_CONFIGURE_LOGGING:
        return

    if process_name is None:
        process_name = get_mp_context().current_process().name

    pid = os.getpid()
    _add_prefix(sys.stdout, process_name, pid)
    _add_prefix(sys.stderr, process_name, pid)

def find_loaded_library(lib_name: str) -> str | None:
    """
    According to according to https://man7.org/linux/man-pages/man5/proc_pid_maps.5.html,
    the file `/proc/self/maps` contains the memory maps of the process, which includes the
    shared libraries loaded by the process. We can use this file to find the path of the
    loaded library.
    """  # noqa
    found_line = None
    with open("/proc/self/maps") as f:
        for line in f:
            if lib_name in line:
                found_line = line
                break
    if found_line is None:
        # the library is not loaded in the current process
        return None
    # if lib_name is libcudart, we need to match a line with:
    # address /path/to/libcudart-hash.so.11.0
    start = found_line.index("/")
    path = found_line[start:].strip()
    filename = path.split("/")[-1]
    assert filename.rpartition(".so")[0].startswith(lib_name), (
        f"Unexpected filename: {filename} for library {lib_name}"
    )
    return path

def get_mp_context():
    """Get a multiprocessing context with a particular method (spawn or fork).
    By default we follow the value of the VLLM_WORKER_MULTIPROC_METHOD to
    determine the multiprocessing method (default is fork). However, under
    certain conditions, we may enforce spawn and override the value of
    VLLM_WORKER_MULTIPROC_METHOD.
    """
    _maybe_force_spawn()
    mp_method = envs.VLLM_WORKER_MULTIPROC_METHOD
    return multiprocessing.get_context(mp_method)

def kill_process_tree(pid: int):
    """
    Kills all descendant processes of the given pid by sending SIGKILL.

    Args:
        pid (int): Process ID of the parent process
    """
    try:
        parent = psutil.Process(pid)
    except psutil.NoSuchProcess:
        return

    # Get all children recursively
    children = parent.children(recursive=True)

    # Send SIGKILL to all children first
    for child in children:
        with contextlib.suppress(ProcessLookupError):
            os.kill(child.pid, signal.SIGKILL)

    # Finally kill the parent
    with contextlib.suppress(ProcessLookupError):
        os.kill(pid, signal.SIGKILL)

@contextlib.contextmanager
def set_env_var(key: str, value: str) -> Iterator[None]:
    """Temporarily set an environment variable."""
    old = os.environ.get(key)
    os.environ[key] = value
    try:
        yield
    finally:
        if old is None:
            os.environ.pop(key, None)
        else:
            os.environ[key] = old

def set_process_title(
    name: str,
    suffix: str = "",
    prefix: str = envs.VLLM_PROCESS_NAME_PREFIX,
) -> None:
    """Set the current process title with optional suffix."""
    try:
        import setproctitle
    except ImportError:
        return

    if suffix:
        name = f"{name}_{suffix}"

    setproctitle.setproctitle(f"{prefix}::{name}")

def set_ulimit(target_soft_limit: int = 65535):
    if sys.platform.startswith("win"):
        logger.info("Windows detected, skipping ulimit adjustment.")
        return

    import resource

    resource_type = resource.RLIMIT_NOFILE
    current_soft, current_hard = resource.getrlimit(resource_type)

    if current_soft < target_soft_limit:
        try:
            resource.setrlimit(resource_type, (target_soft_limit, current_hard))
        except ValueError as e:
            logger.warning(
                "Found ulimit of %s and failed to automatically increase "
                "with error %s. This can cause fd limit errors like "
                "`OSError: [Errno 24] Too many open files`. Consider "
                "increasing with ulimit -n",
                current_soft,
                e,
            )

@contextlib.contextmanager
def suppress_stdout():
    """
    Suppress stdout from C libraries at the file descriptor level.

    Only suppresses stdout, not stderr, to preserve error messages.
    Suppression is disabled when VLLM_LOGGING_LEVEL is set to DEBUG.

    Example:
        with suppress_stdout():
            # C library calls that would normally print to stdout
            torch.distributed.new_group(ranks, backend="gloo")
    """
    # Don't suppress if logging level is DEBUG
    if envs.VLLM_LOGGING_LEVEL == "DEBUG":
        yield
        return

    stdout_fd = sys.stdout.fileno()
    stdout_dup = os.dup(stdout_fd)
    devnull_fd = os.open(os.devnull, os.O_WRONLY)

    try:
        sys.stdout.flush()
        os.dup2(devnull_fd, stdout_fd)
        yield
    finally:
        sys.stdout.flush()
        os.dup2(stdout_dup, stdout_fd)
        os.close(stdout_dup)
        os.close(devnull_fd)

def unique_filepath(fn: Callable[[int], Path]) -> Path:
    """Generate a unique file path by trying incrementing integers.

    Note: This function has a TOCTOU race condition.
    Caller should use atomic operations (e.g., open with 'x' mode)
    when creating the file to ensure thread safety.
    """
    i = 0
    while True:
        p = fn(i)
        if not p.exists():
            return p
        i += 1

def update_environment_variables(envs_dict: dict[str, str]):
    """Update multiple environment variables with logging."""
    for k, v in envs_dict.items():
        if k in os.environ and os.environ[k] != v:
            logger.warning(
                "Overwriting environment variable %s from '%s' to '%s'",
                k,
                os.environ[k],
                v,
            )
        os.environ[k] = v