Set log level to warning instead of error for 4xx HTTPExceptions from FastAPI/Starlette

logfire/_internal/tracer.py

@@ -356,11 +356,14 @@ def record_exception(
     escaped: bool = False,
 ) -> None:
     """Similar to the OTEL SDK Span.record_exception method, with our own additions."""
+    if is_starlette_http_exception_400(exception):
+        span.set_attributes(log_level_attributes('warn'))
+
     # From https://opentelemetry.io/docs/specs/semconv/attributes-registry/exception/
     # `escaped=True` means that the exception is escaping the scope of the span.
     # This means we know that the exception hasn't been handled,
     # so we can set the OTEL status and the log level to error.
-    if escaped:
+    elif escaped:
         set_exception_status(span, exception)
         span.set_attributes(log_level_attributes('error'))
 
@@ -392,3 +395,12 @@ def set_exception_status(span: trace_api.Span, exception: BaseException):
             description=f'{exception.__class__.__name__}: {exception}',
         )
     )
+
+
+def is_starlette_http_exception_400(exception: BaseException) -> bool:
+    if 'starlette.exceptions' not in sys.modules:  # pragma: no cover
+        return False
+
+    from starlette.exceptions import HTTPException
+
+    return isinstance(exception, HTTPException) and 400 <= exception.status_code < 500

tests/otel_integrations/test_fastapi.py

@@ -8,7 +8,7 @@
 import pytest
 from dirty_equals import IsJson
 from fastapi import BackgroundTasks, FastAPI, Response, WebSocket
-from fastapi.exceptions import RequestValidationError
+from fastapi.exceptions import HTTPException, RequestValidationError
 from fastapi.params import Header
 from fastapi.security import SecurityScopes
 from fastapi.staticfiles import StaticFiles
@@ -23,6 +23,7 @@
 import logfire._internal
 import logfire._internal.integrations
 import logfire._internal.integrations.fastapi
+from logfire._internal.constants import LEVEL_NUMBERS
 from logfire._internal.main import set_user_attributes_on_raw_span
 from logfire.testing import TestExporter
 
@@ -74,6 +75,10 @@ async def echo_body(request: Request):
     return await request.body()
 
 
+async def bad_request_error():
+    raise HTTPException(400)
+
+
 async def websocket_endpoint(websocket: WebSocket, name: str):
     logfire.info('websocket_endpoint: {name}', name=name)
     await websocket.accept()
@@ -97,6 +102,7 @@ def app():
     app.get('/other', name='other_route_name', operation_id='other_route_operation_id')(other_route)
     app.get('/exception')(exception)
     app.get('/validation_error')(validation_error)
+    app.get('/bad_request_error')(bad_request_error)
     app.get('/with_path_param/{param}')(with_path_param)
     app.get('/secret/{path_param}', name='secret')(get_secret)
     app.websocket('/ws/{name}')(websocket_endpoint)
@@ -192,6 +198,14 @@ def test_404(client: TestClient, exporter: TestExporter) -> None:
     )
 
 
+def test_400(client: TestClient, exporter: TestExporter) -> None:
+    response = client.get('/bad_request_error')
+    assert response.status_code == 400
+
+    [span] = [span for span in exporter.exported_spans if span.events]
+    assert span.attributes and span.attributes['logfire.level_num'] == LEVEL_NUMBERS['warn']
+
+
 def test_path_param(client: TestClient, exporter: TestExporter) -> None:
     response = client.get('/with_path_param/param_val')
     assert response.status_code == 200