Files
agent_delta/backend/app/api/exception_handlers.py
T
2026-06-15 14:22:07 +08:00

109 lines
3.2 KiB
Python

"""Exception handlers for FastAPI application.
These handlers convert domain exceptions to proper HTTP responses.
WebSocket connections that raise an ``AppException`` before ``accept()`` are
handled too — Starlette closes the socket with 403 and we just log the
incident; we cannot return an HTTP body for a non-HTTP scope.
"""
import logging
from typing import Any
from fastapi import FastAPI
from fastapi.responses import JSONResponse
from starlette.requests import HTTPConnection
from app.core.exceptions import AppException
logger = logging.getLogger(__name__)
def _connection_meta(conn: HTTPConnection) -> dict[str, Any]:
"""Common log fields shared by HTTP requests and WebSocket connections.
``method`` exists only on HTTP ``Request`` — for WebSockets we surface the
scope type so log filters can still distinguish the two.
"""
return {
"path": conn.url.path,
"method": getattr(conn, "method", None) or conn.scope.get("type", "unknown"),
}
def _is_websocket(conn: HTTPConnection) -> bool:
return conn.scope.get("type") == "websocket"
async def app_exception_handler(request: HTTPConnection, exc: AppException) -> JSONResponse | None:
"""Handle application exceptions for both HTTP and WebSocket scopes.
Logs 5xx errors as errors and 4xx as warnings. Returns a JSON response
for HTTP scopes; returns ``None`` for WebSocket scopes (Starlette will
close the socket on its own).
"""
log_extra = {
"error_code": exc.code,
"status_code": exc.status_code,
"details": exc.details,
**_connection_meta(request),
}
if exc.status_code >= 500:
logger.error(f"{exc.code}: {exc.message}", extra=log_extra)
else:
logger.warning(f"{exc.code}: {exc.message}", extra=log_extra)
if _is_websocket(request):
return None
headers: dict[str, str] = {}
if exc.status_code == 401:
headers["WWW-Authenticate"] = "Bearer"
return JSONResponse(
status_code=exc.status_code,
content={
"error": {
"code": exc.code,
"message": exc.message,
"details": exc.details or None,
}
},
headers=headers,
)
async def unhandled_exception_handler(
request: HTTPConnection, exc: Exception
) -> JSONResponse | None:
"""Handle unexpected exceptions.
Logs the full exception but returns a generic error to the client
to avoid leaking sensitive information.
"""
logger.exception("Unhandled exception", extra=_connection_meta(request))
if _is_websocket(request):
return None
return JSONResponse(
status_code=500,
content={
"error": {
"code": "INTERNAL_ERROR",
"message": "An unexpected error occurred",
"details": None,
}
},
)
def register_exception_handlers(app: FastAPI) -> None:
"""Register all exception handlers on the FastAPI app.
Call this after creating the FastAPI application instance.
"""
app.add_exception_handler(AppException, app_exception_handler)
# Uncomment to catch all unhandled exceptions:
# app.add_exception_handler(Exception, unhandled_exception_handler)