[feature] add log non default args in LLM

[lengrongfu]

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Purpose

When use LLM class to running mode, log non default args, like cli args.

Test Plan

Test Result

(Optional) Documentation Update

[github-actions]

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[gemini-code-assist]

Code Review

This pull request introduces a useful feature to log non-default arguments when initializing an LLM instance. However, the implementation has a critical issue where it unsafely retrieves default values by instantiating EngineArgs, which can cause side effects. Additionally, the new logging function is missing the logger definition, which would lead to a runtime error. I've provided a suggestion to fix the function's logic and pointed out the missing logger definition.

[gemini-code-assist]

This function has two critical issues:

1. NameError for logger: The logger object is used but not defined or imported in this file. This will cause a NameError at runtime. You need to import init_logger from vllm.logger and initialize it at the module level, e.g., logger = init_logger(__name__).

2. Unsafe default value retrieval: Instantiating EngineArgs() to get default values is problematic as it executes EngineArgs.__post_init__, which has side effects (e.g., load_general_plugins()). This is inefficient and can lead to subtle bugs. A safer approach is to get default values directly from the dataclass field definitions.

Here is a corrected version of the function. Please also ensure you add the logger import and initialization at the top of the file.

def log_non_default_args(args: EngineArgs):
    """Log non-default arguments from EngineArgs.

    This function compares the current EngineArgs instance values with the
    default values defined in the dataclass and logs any differences.

    Args:
        args: The EngineArgs instance to check for non-default values.
    """
    non_default_args = {}
    for field in dataclasses.fields(EngineArgs):
        field_name = field.name
        current_value = getattr(args, field_name)

        # Get default value from the field definition to avoid
        # instantiating EngineArgs and triggering side effects in __post_init__.
        if field.default is not dataclasses.MISSING:
            default_value = field.default
        elif field.default_factory is not dataclasses.MISSING:
            default_value = field.default_factory()
        else:
            # This should not happen for EngineArgs as all fields have defaults.
            continue

        # Compare current value with default value
        if current_value != default_value:
            non_default_args[field_name] = current_value

    if non_default_args:
        logger.info("Using non-default arguments: %s", non_default_args)

[DarkLight1337]

Can we consolidate this code with that for online inference?

[lengrongfu]

Can we consolidate this code with that for online inference?

Thanks, Merge into the same method.

[DarkLight1337]

LGTM, thanks