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vllm.logging_utils

Modules:

Name Description
dump_input
formatter
lazy
log_time

Provides a timeslice logging decorator

__all__ module-attribute 

__all__ = [
    "NewLineFormatter",
    "ColoredFormatter",
    "lazy",
    "logtime",
]

ColoredFormatter

Bases: NewLineFormatter

Adds ANSI color codes to log levels for terminal output.

This formatter adds colors by injecting them into the format string for static elements (timestamp, filename, line number) and modifying the levelname attribute for dynamic color selection.

Source code in vllm/logging_utils/formatter.py 
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class ColoredFormatter(NewLineFormatter):
    """Adds ANSI color codes to log levels for terminal output.

    This formatter adds colors by injecting them into the format string for
    static elements (timestamp, filename, line number) and modifying the
    levelname attribute for dynamic color selection.
    """

    # ANSI color codes
    COLORS = {
        "DEBUG": "\033[37m",  # White
        "INFO": "\033[32m",  # Green
        "WARNING": "\033[33m",  # Yellow
        "ERROR": "\033[31m",  # Red
        "CRITICAL": "\033[35m",  # Magenta
    }
    GREY = "\033[90m"  # Grey for timestamp and file info
    RESET = "\033[0m"

    def __init__(self, fmt, datefmt=None, style="%"):
        # Inject grey color codes into format string for timestamp and file info
        if fmt:
            # Wrap %(asctime)s with grey
            fmt = fmt.replace("%(asctime)s", f"{self.GREY}%(asctime)s{self.RESET}")
            # Wrap [%(fileinfo)s:%(lineno)d] with grey
            fmt = fmt.replace(
                "[%(fileinfo)s:%(lineno)d]",
                f"{self.GREY}[%(fileinfo)s:%(lineno)d]{self.RESET}",
            )

        # Call parent __init__ with potentially modified format string
        super().__init__(fmt, datefmt, style)

    def format(self, record):
        # Store original levelname to restore later (in case record is reused)
        orig_levelname = record.levelname

        # Only modify levelname - it needs dynamic color based on severity
        if (color_code := self.COLORS.get(record.levelname)) is not None:
            record.levelname = f"{color_code}{record.levelname}{self.RESET}"

        # Call parent format which will handle everything else
        msg = super().format(record)

        # Restore original levelname
        record.levelname = orig_levelname

        return msg

COLORS class-attribute instance-attribute 

COLORS = {
    "DEBUG": "\x1b[37m",
    "INFO": "\x1b[32m",
    "WARNING": "\x1b[33m",
    "ERROR": "\x1b[31m",
    "CRITICAL": "\x1b[35m",
}

GREY class-attribute instance-attribute 

GREY = '\x1b[90m'

RESET class-attribute instance-attribute 

RESET = '\x1b[0m'

__init__ 

__init__(fmt, datefmt=None, style='%')
Source code in vllm/logging_utils/formatter.py 
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def __init__(self, fmt, datefmt=None, style="%"):
    # Inject grey color codes into format string for timestamp and file info
    if fmt:
        # Wrap %(asctime)s with grey
        fmt = fmt.replace("%(asctime)s", f"{self.GREY}%(asctime)s{self.RESET}")
        # Wrap [%(fileinfo)s:%(lineno)d] with grey
        fmt = fmt.replace(
            "[%(fileinfo)s:%(lineno)d]",
            f"{self.GREY}[%(fileinfo)s:%(lineno)d]{self.RESET}",
        )

    # Call parent __init__ with potentially modified format string
    super().__init__(fmt, datefmt, style)

format 

format(record)
Source code in vllm/logging_utils/formatter.py 
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def format(self, record):
    # Store original levelname to restore later (in case record is reused)
    orig_levelname = record.levelname

    # Only modify levelname - it needs dynamic color based on severity
    if (color_code := self.COLORS.get(record.levelname)) is not None:
        record.levelname = f"{color_code}{record.levelname}{self.RESET}"

    # Call parent format which will handle everything else
    msg = super().format(record)

    # Restore original levelname
    record.levelname = orig_levelname

    return msg

NewLineFormatter

Bases: Formatter

Adds logging prefix to newlines to align multi-line messages.

Source code in vllm/logging_utils/formatter.py 
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class NewLineFormatter(logging.Formatter):
    """Adds logging prefix to newlines to align multi-line messages."""

    def __init__(self, fmt, datefmt=None, style="%"):
        super().__init__(fmt, datefmt, style)

        self.use_relpath = envs.VLLM_LOGGING_LEVEL == "DEBUG"
        if self.use_relpath:
            self.root_dir = Path(__file__).resolve().parent.parent.parent

    def format(self, record):
        def shrink_path(relpath: Path) -> str:
            """
            Shortens a file path for logging display:
            - Removes leading 'vllm' folder if present.
            - If path starts with 'v1',
            keeps the first two and last two levels,
            collapsing the middle as '...'.
            - Otherwise, keeps the first and last two levels,
            collapsing the middle as '...'.
            - If the path is short, returns it as-is.
            - Examples:
            vllm/model_executor/layers/quantization/utils/fp8_utils.py ->
            model_executor/.../quantization/utils/fp8_utils.py
            vllm/model_executor/layers/quantization/awq.py ->
            model_executor/layers/quantization/awq.py
            vllm/v1/attention/backends/mla/common.py ->
            v1/attention/backends/mla/common.py

            Args:
                relpath (Path): The relative path to be shortened.
            Returns:
                str: The shortened path string for display.
            """
            parts = list(relpath.parts)
            new_parts = []
            if parts and parts[0] == "vllm":
                parts = parts[1:]
            if parts and parts[0] == "v1":
                new_parts += parts[:2]
                parts = parts[2:]
            elif parts:
                new_parts += parts[:1]
                parts = parts[1:]
            if len(parts) > 2:
                new_parts += ["..."] + parts[-2:]
            else:
                new_parts += parts
            return "/".join(new_parts)

        if self.use_relpath:
            abs_path = getattr(record, "pathname", None)
            if abs_path:
                try:
                    relpath = Path(abs_path).resolve().relative_to(self.root_dir)
                except Exception:
                    relpath = Path(record.filename)
            else:
                relpath = Path(record.filename)
            record.fileinfo = shrink_path(relpath)
        else:
            record.fileinfo = record.filename

        msg = super().format(record)
        if record.message != "":
            parts = msg.split(record.message)
            msg = msg.replace("\n", "\r\n" + parts[0])
        return msg

root_dir instance-attribute 

root_dir = parent

use_relpath instance-attribute 

use_relpath = VLLM_LOGGING_LEVEL == 'DEBUG'

__init__ 

__init__(fmt, datefmt=None, style='%')
Source code in vllm/logging_utils/formatter.py 
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def __init__(self, fmt, datefmt=None, style="%"):
    super().__init__(fmt, datefmt, style)

    self.use_relpath = envs.VLLM_LOGGING_LEVEL == "DEBUG"
    if self.use_relpath:
        self.root_dir = Path(__file__).resolve().parent.parent.parent

format 

format(record)
Source code in vllm/logging_utils/formatter.py 
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def format(self, record):
    def shrink_path(relpath: Path) -> str:
        """
        Shortens a file path for logging display:
        - Removes leading 'vllm' folder if present.
        - If path starts with 'v1',
        keeps the first two and last two levels,
        collapsing the middle as '...'.
        - Otherwise, keeps the first and last two levels,
        collapsing the middle as '...'.
        - If the path is short, returns it as-is.
        - Examples:
        vllm/model_executor/layers/quantization/utils/fp8_utils.py ->
        model_executor/.../quantization/utils/fp8_utils.py
        vllm/model_executor/layers/quantization/awq.py ->
        model_executor/layers/quantization/awq.py
        vllm/v1/attention/backends/mla/common.py ->
        v1/attention/backends/mla/common.py

        Args:
            relpath (Path): The relative path to be shortened.
        Returns:
            str: The shortened path string for display.
        """
        parts = list(relpath.parts)
        new_parts = []
        if parts and parts[0] == "vllm":
            parts = parts[1:]
        if parts and parts[0] == "v1":
            new_parts += parts[:2]
            parts = parts[2:]
        elif parts:
            new_parts += parts[:1]
            parts = parts[1:]
        if len(parts) > 2:
            new_parts += ["..."] + parts[-2:]
        else:
            new_parts += parts
        return "/".join(new_parts)

    if self.use_relpath:
        abs_path = getattr(record, "pathname", None)
        if abs_path:
            try:
                relpath = Path(abs_path).resolve().relative_to(self.root_dir)
            except Exception:
                relpath = Path(record.filename)
        else:
            relpath = Path(record.filename)
        record.fileinfo = shrink_path(relpath)
    else:
        record.fileinfo = record.filename

    msg = super().format(record)
    if record.message != "":
        parts = msg.split(record.message)
        msg = msg.replace("\n", "\r\n" + parts[0])
    return msg

logtime 

logtime(logger, msg=None)

Logs the execution time of the decorated function. Always place it beneath other decorators.

Source code in vllm/logging_utils/log_time.py 
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def logtime(logger, msg=None):
    """
    Logs the execution time of the decorated function.
    Always place it beneath other decorators.
    """

    def _inner(func):
        @functools.wraps(func)
        def _wrapper(*args, **kwargs):
            start = time.perf_counter()
            result = func(*args, **kwargs)
            elapsed = time.perf_counter() - start

            prefix = (
                f"Function '{func.__module__}.{func.__qualname__}'"
                if msg is None
                else msg
            )
            logger.debug("%s: Elapsed time %.7f secs", prefix, elapsed)
            return result

        return _wrapper

    return _inner