aio-libs/aiohttp · error · RuntimeError

Cannot register a resource into frozen router.

Error message

Cannot register a resource into frozen router.

What it means

Error "Cannot register a resource into frozen router." thrown in aio-libs/aiohttp.

Source

Thrown at aiohttp/web_urldispatcher.py:1045

    def __getitem__(self, name: str) -> AbstractResource:
        return self._named_resources[name]

    def resources(self) -> ResourcesView:
        return ResourcesView(self._resources)

    def routes(self) -> RoutesView:
        return RoutesView(self._resources)

    def named_resources(self) -> Mapping[str, AbstractResource]:
        return MappingProxyType(self._named_resources)

    def register_resource(self, resource: AbstractResource) -> None:
        assert isinstance(
            resource, AbstractResource
        ), f"Instance of AbstractResource class is required, got {resource!r}"
        if self.frozen:
            raise RuntimeError("Cannot register a resource into frozen router.")

        name = resource.name

        if name is not None:
            parts = self.NAME_SPLIT_RE.split(name)
            for part in parts:
                if keyword.iskeyword(part):
                    raise ValueError(
                        f"Incorrect route name {name!r}, "
                        "python keywords cannot be used "
                        "for route name"
                    )
                if not part.isidentifier():
                    raise ValueError(
                        f"Incorrect route name {name!r}, "
                        "the name should be a sequence of "
                        "python identifiers separated "
                        "by dash, dot or column"

View on GitHub (pinned to c0ef574e29)

When it happens

Trigger: Thrown at aiohttp/web_urldispatcher.py:1045 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of aio-libs/aiohttp@c0ef574e29 (2026-08-04). Data as JSON: /data/errors/c663861a1c9b64a7.json. Report an issue: GitHub.