sgl-project/sglang · error · ValueError

_load_function expects 'pkg.module.symbol', got {path!r} (mi

Error message

_load_function expects 'pkg.module.symbol', got {path!r} (missing dotted prefix)

What it means

Raised by the internal _load_function helper when the path argument has no dotted module prefix, i.e. rpartition('.') finds no '.' so module_path is empty. The helper requires a fully qualified 'pkg.module.symbol' string so it can importlib.import_module the module and getattr the symbol. A bare name like 'foo' cannot be resolved to any module.

Source

Thrown at python/sglang/srt/debug_utils/dumper.py:1582

        s.connect(("2001:4860:4860::8888", 80))  # Doesn't need to be reachable
        return s.getsockname()[0]
    except Exception:
        _log("Can not get local ip by remote")
    return None


def _load_function(path: str) -> Callable:
    """Resolve a fully-qualified Python path 'pkg.module.symbol' to its object.

    Copied (verbatim, minus the function-registry branch) from
    miles.utils.misc.load_function — kept inline so dumper.py has no
    cross-package dependency.
    """
    import importlib

    module_path, _, attr = path.rpartition(".")
    if not module_path:
        raise ValueError(
            f"_load_function expects 'pkg.module.symbol', got {path!r} "
            f"(missing dotted prefix)"
        )
    module = importlib.import_module(module_path)
    return getattr(module, attr)


def _init_custom_process_group(
    *,
    backend: str,
    init_method: str,
    world_size: int,
    rank: int,
    group_name: str,
    timeout=None,
):
    """Build a fresh torch.distributed process group, separate from the default
    one and any other custom groups (e.g. RLHF weight-update groups). Used by

View on GitHub (pinned to 0132848349)

Solutions

Use the fully qualified path including package and module, e.g. 'sglang.srt.layers.mymodule.myfunc'
Verify the module imports cleanly in a REPL before configuring it (python -c "import pkg.module")
If loading from config, print/validate the path at config load time to catch typos early

Example fix

# before
_load_function('capture_dump')

# after
_load_function('sglang.srt.debug_utils.hooks.capture_dump')

Defensive patterns

Strategy: validation

Validate before calling

def is_valid_load_path(path: str) -> bool:
    return bool(path) and '.' in path and path.rpartition('.')[0].isidentifier() is not None

assert is_valid_load_path(path), f"path must be 'pkg.module.symbol', got {path!r}"

Type guard

def is_qualified_symbol_path(path: str) -> bool:
    parts = path.split('.')
    return len(parts) >= 2 and all(p.isidentifier() for p in parts) and not path.startswith('.') and not path.endswith('.')

Try / catch

try:
    fn = _load_function(path)
except ValueError:
    raise ConfigError(f'hook path {path!r} must be pkg.module.symbol') from None

Prevention

Always write hook paths fully qualified including the package
Validate configured paths at startup, not at first use
Test that the module imports in the target environment

When it happens

Trigger: Calling _load_function('myfunc') or _load_function('') — any string without a dot. Typical when a debug/dump hook path is configured via SGLANG_DEBUG env vars or YAML config and the user gave just the function name instead of the full dotted path.

Common situations: Misconfigured debug hook paths in environment variables or patch YAML files; refactoring moved a function to a new module and someone shortened the path; copy-paste from docs that omitted the package prefix.

Related errors

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/28797d8b7e2ae65b. Report an issue: GitHub.