The /predict endpoint in the example servers does not define a request body schema. Consequently, Swagger UI provides no input form and sends an empty request body by default when "Execute" is clicked. This results in a 500 Internal Server Error as the server fails to parse the empty JSON payload.
To Reproduce
1. Start the server
python tests/simple_server_diff_port.py
2. Access Swagger UI
Navigate to:
http://localhost:8000/docs
3. Trigger the Error
- Expand the
/predict endpoint
- Click Execute
Note: No input field is visible to the user.
Actual Results
The server crashes with a JSONDecodeError because Swagger sends an empty body:
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
...
File "src/litserve/server.py", line X, in predict
return await request.json()
Expected Behavior
Swagger UI should display a request body form (e.g., a JSON blob like below). This allows users to provide input values directly in the interface, ensuring the request.json() call has valid data to parse.
Suggested Fix: Implement Pydantic Schemas
To resolve this, define a Pydantic model for the request payload. This allows the underlying FastAPI engine to generate the proper OpenAPI documentation for Swagger.
Proposed change
from pydantic import BaseModel
from typing import Any
# Define the expected schema
class PredictRequest(BaseModel):
input: Any
# Update the endpoint logic to reference this schema
# so Swagger generates the following interactive form:
# {
# "input": "value"
# }Environment
- OS: Linux
- Python: 3.12
- Installation: pip
The
/predictendpoint in the example servers does not define a request body schema. Consequently, Swagger UI provides no input form and sends an empty request body by default when "Execute" is clicked. This results in a 500 Internal Server Error as the server fails to parse the empty JSON payload.To Reproduce
1. Start the server
2. Access Swagger UI
Navigate to:
3. Trigger the Error
/predictendpointNote: No input field is visible to the user.
Actual Results
The server crashes with a JSONDecodeError because Swagger sends an empty body:
Expected Behavior
Swagger UI should display a request body form (e.g., a JSON blob like below). This allows users to provide input values directly in the interface, ensuring the
request.json()call has valid data to parse.{ "input": 5 }Suggested Fix: Implement Pydantic Schemas
To resolve this, define a Pydantic model for the request payload. This allows the underlying FastAPI engine to generate the proper OpenAPI documentation for Swagger.
Proposed change
Environment