{"slug": "persistent-503-error-between-private-docker-spaces", "title": "Persistent 503 Error Between Private Docker Spaces", "summary": "Hugging Face users report a persistent 503 error when making server-side requests from one private Docker Space to another, despite individual features being documented as supported. The issue appears to be a regression since July 8, as external requests succeed while internal Space-to-Space calls fail. Hugging Face is urged to clarify whether cross-Space requests are still intended to work or provide a documented alternative.", "body_md": "Personally, this (and [Space-to-Space requests to *.hf.space return 503 from awselb (since Jul 8)](https://discuss.huggingface.co/t/space-to-space-requests-to-hf-space-return-503-from-awselb-since-jul-8/177607)) looks more like a regression to me. Details below:\n\njust in case, [@hysts](https://discuss.huggingface.co/u/hysts)\n\n**Direct answer:** the general architecture does not appear to be inherently unsupported.\n\nHugging Face documents Docker Spaces as suitable for [FastAPI and other API endpoints](https://huggingface.co/docs/hub/spaces-sdks-docker), documents authenticated access to private Space endpoints, and also documents [calling one Space from another Space](https://huggingface.co/docs/hub/spaces-api-endpoints). I could not find one official reference that combines this exact topology—private Docker caller, private Docker target, arbitrary FastAPI route, and server-side Bearer authentication—but the individual pieces are documented or have prior working examples.\n\nFor a private Docker Space, the route I would expect to use is still:\n\n```\ncaller Space\n    → HTTPS on port 443\n    → https://<target-subdomain>.hf.space/<route>\n    → Authorization: Bearer <token that can access the target Space>\n    → target application\n```\n\nThe [Docker Spaces documentation](https://huggingface.co/docs/hub/spaces-sdks-docker) describes exposing an application through `app_port`\n\n, and the [Spaces networking documentation](https://huggingface.co/docs/hub/spaces-overview#networking) allows outbound HTTP/HTTPS traffic on ports 80 and 443. The official [private Tabby Docker Space example](https://github.com/huggingface/hub-docs/blob/main/docs/hub/spaces-sdks-docker-tabby.md) also uses the direct `*.hf.space`\n\nURL as an API endpoint and adds an authorization header when the Space is private.\n\nThe strongest reason I would currently suspect a regression is the independent report in [Space-to-Space requests to *.hf.space return 503 from awselb](https://discuss.huggingface.co/t/space-to-space-requests-to-hf-space-return-503-from-awselb-since-jul-8/177607). That report describes:\n\n`200`\n\noutside Hugging Face but `503`\n\nfrom inside a Space;If those controls are accurate, this is difficult to explain purely as a Dockerfile, FastAPI route, token-scope, private-visibility, DNS, or single-Space deployment problem.\n\nFor now, I would **pause large application-side changes**. Rebuilding all five Spaces again, changing the model-loading code, or increasing retries is unlikely to isolate a source-dependent platform issue. A small inside-vs-outside comparison with exact timestamps is likely to be more useful.\n\n`awselb`\n\nheader or the missing Run Log entry. It is the independently reported difference between an external caller receiving `200`\n\nand a Space caller receiving `503`\n\nfrom the same target.The key question for HF is whether server-side requests from one Space to another `*.hf.space`\n\nendpoint are still intended to work. If they are, the current evidence appears to warrant platform-side investigation. If they are not, the supported replacement route needs to be documented.", "url": "https://wpnews.pro/news/persistent-503-error-between-private-docker-spaces", "canonical_source": "https://discuss.huggingface.co/t/persistent-503-error-between-private-docker-spaces/177610#post_2", "published_at": "2026-07-09 07:59:28+00:00", "updated_at": "2026-07-09 08:22:38.515356+00:00", "lang": "en", "topics": ["developer-tools", "ai-infrastructure"], "entities": ["Hugging Face", "Docker"], "alternates": {"html": "https://wpnews.pro/news/persistent-503-error-between-private-docker-spaces", "markdown": "https://wpnews.pro/news/persistent-503-error-between-private-docker-spaces.md", "text": "https://wpnews.pro/news/persistent-503-error-between-private-docker-spaces.txt", "jsonld": "https://wpnews.pro/news/persistent-503-error-between-private-docker-spaces.jsonld"}}