Docker Space POST endpoint 404/HTML error — routing never reaches FastAPI container

Spaces
1

Summary:
My Docker Space builds fine and responds on GET /, but all POST requests to my defined /api/predict-emotion route return a 404 HTML page (not a 500/json). Logs never show POST requests. I havw tried every documented troubleshooting step; please help!

My Setup:

  • All files (app.py, Dockerfile, requirements.txt, models, etc.) are at repo root
  • Dockerfile ends with:
    EXPOSE 7860
    CMD [“uvicorn”, “app:app”, “–host”, “0.0.0.0”, “–port”, “7860”]
  • Space type is set to Docker
  • After every change, I use Restart and Rebuild

Observed result:

  • I get an HTML 404 (Hugging Face “can’t find page”) as if the route doesn’t exist :frowning:
  • No POST log lines ever appear in Spaces “App logs”; only GET requests to “/” are logged.

I have tried:

  • New minimal Space with simple slug (no underscores)
  • All files at root, no subfolders
  • Minimal app.py to remove possible Python/package bugs
  • Rebuilding
  • Requirements and Dockerfile match all best practices

What I need:

  • How do I get POST requests routed to my container/app?
  • Why does the Space infra keep returning Hugging Face HTML 404 for POST, but work for GET?

Any rapid response or internal routing check would be greatly appreciated! :slight_smile:

1 Like
2

How do I get POST requests routed to my container/app?

It seems that Post requests do not go through unless you are using the hf.space domain. Like this:

https://<username>-<space>.hf.space/api/predict
3

Hi @John6666, thank you so much for your quick reply. I checked and I am POSTing to the correct .hf.space endpoint, still getting 404 HTML. No POST lines in logs. I have rebuilt and even tried a new Space with only minimal app.py. I am thinking if this is an infra/routing bug.

1 Like
4

Well, if it’s a bug, I don’t know where to report it. I guess we could just email support, but it would be better to verify the bug openly if possible…

I’ve heard that bugs related to the hub in general can be reported to hub-docs.

1 Like
5

Thank you so much for your speedy and consistent replies. I am trying email support because the hub-docs looks more appropriate for documentation support. Fingers crossed.

1 Like
6

Try this fix, hope so it will solve it

The most likely problem is in your Dockerfile command. Try changing this line:

Current:CMD ["uvicorn", "app:app", "–host", "0.0.0.0", "–port", "7860"]

Fix: CMD ["uvicorn", "app:app", "--host", "0.0.0.0", "--port", "7860"]

(Notice the double dashes -- instead of single dashes)

If That Doesn’t Work

Add this to your app.py to help with routing:

from fastapi.middleware.cors import CORSMiddleware

app.add_middleware(
CORSMiddleware,
allow_origins=[““],
allow_methods=[””],
allow_headers=[“*”],
)

The do a quick test.

Add a simple POST route to test:

@app.post(“/test”)
async def test_post():
return {“message”: “POST works!”}

That’s it! The issue is with how Hugging Face routes requests to your container, not your code. These small changes should fix it. Good luck!

2 Likes
7

@Angelina067 Thank you so much for such a concrete suggestion. Sadly, I have tried everything you said but it’s still not working :frowning:

INFO:emotion-backend:Model loaded OK.
INFO: Started server process [1]
INFO: Waiting for application startup.
INFO: Application startup complete.
INFO: Uvicorn running on http://0.0.0.0:7860 (Press CTRL+C to quit)

And I am getting getting 404 HTML on POST

1 Like
8

OMG! So sorry. Its frustrating! Since your server is running fine but Hugging Face is still returning HTML 404s for POST requests, this is definitely a Hugging Face Spaces infrastructure issue.

I think Hugging Face Spaces has routing limitations - it’s designed primarily for GET requests (web interfaces) and doesn’t always handle POST requests to custom API endpoints properly.

May be you should use the Root Path (Easiest Fix), Move your endpoint to the root:

@app.post(“/”) # Instead of “/api/predict-emotion”
async def predict_emotion(request):
return {“result”: “success”}

Or add a Gradio Interface (Most Reliable), Hugging Face Spaces works best with Gradio:

import gradio as gr

def predict_emotion(text):
# Your prediction logic here
return “emotion result”

Create Gradio interface

demo = gr.Interface(fn=predict_emotion, inputs=“text”, outputs=“text”)
demo.launch()

✓ Consider using their hosted inference API rather than a custom Docker space for POST endpoints.

P.s: The issue is that Hugging Face Spaces infrastructure doesn’t properly route POST requests to custom API endpoints. This is a known limitation. The quickest fix is either moving the endpoint to the root path or using a Gradio interface, which Hugging Face Spaces is optimized for.

This isn’t a code problem - it’s a Hugging Face Spaces platform limitation with POST routing.

Stay blessed!

1 Like
9

Thank you so much for your empathy and kindness and most importantly your reply!! I feel really frustrated :frowning: I am working on it, will reply soon.

1 Like
10

Emotion Detection - a Hugging Face Space by boloappde I put the new space in public and used Gradio this time. Initially I used Gradio, and moved to Docker because I thought that would be better, but after enuogh troubleshooting I changed my mind. There’s a problem with the current ML model (only giving outputs as “happy” even when it is not!). After fixing it, I will try to connect it with the web app.

1 Like
11

Okay so finally I had to just embed the Gradio interface to the web app. However I am extremely happy and grateful to both of you @Angelina067 and @John6666. Thank you so much for being so kind and wonderful.

2 Likes