Method fetch

scrapy/core/downloader/__init__.py:126–138

(
        self, request: Request, spider: Spider | None = None
    )

    @inlineCallbacks
    @_warn_spider_arg
    def fetch(
        self, request: Request, spider: Spider | None = None
    ) -> Generator[Deferred[Any], Any, Response | Request]:
        self.active.add(request)
        try:
            result: Response | Request = yield (
                deferred_from_coro(
                    self.middleware.download_async(self._enqueue_request, request)
                )
            )
            return result
        finally:
            self.active.remove(request)

    def needs_backout(self) -> bool:
        return len(self.active) >= self.total_concurrency