fix: release database connections immediately after auth instead of holding during LLM calls (#20545)

fix: release database connections immediately after auth instead of holding during LLM calls

Authentication was using Depends(get_session) which holds a database connection
for the entire request lifecycle. For chat completions, this meant connections
were held for 30-60 seconds while waiting for LLM responses, despite only needing
the connection for ~50ms of actual database work.

With a default pool of 15 connections, this limited concurrent chat users to ~15
before pool exhaustion and timeout errors:

    sqlalchemy.exc.TimeoutError: QueuePool limit of size 5 overflow 10 reached,
    connection timed out, timeout 30.00

The fix removes Depends(get_session) from get_current_user. Each database
operation now manages its own short-lived session internally:

    BEFORE: One session held for entire request
    ──────────────────────────────────────────────────
    │ auth │ queries │ LLM wait (30s) │ save │
    │         CONNECTION HELD ENTIRE TIME            │
    ──────────────────────────────────────────────────

    AFTER: Short-lived sessions, released immediately
    ┌──────┐ ┌───────┐                 ┌──────┐
    │ auth │ │ query │   LLM (30s)     │ save │
    │ 10ms │ │ 20ms  │  NO CONNECTION  │ 20ms │
    └──────┘ └───────┘                 └──────┘

This is safe because:
- User model has no lazy-loaded relationships (all simple columns)
- Pydantic conversion (UserModel.model_validate) happens while session is open
- Returned object is pure Pydantic with no SQLAlchemy ties

Combined with the telemetry efficiency fix, this resolves connection pool
exhaustion for high-concurrency deployments, particularly on network-attached
databases like AWS Aurora where connection hold time is more impactful.

backend/open_webui/utils/auth.py

@@ -44,8 +44,6 @@ from open_webui.env import (
 
 from fastapi import BackgroundTasks, Depends, HTTPException, Request, Response, status
 from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
-from sqlalchemy.orm import Session
-from open_webui.internal.db import get_session
 
 
 log = logging.getLogger(__name__)
@@ -279,7 +277,10 @@ async def get_current_user(
     response: Response,
     background_tasks: BackgroundTasks,
     auth_token: HTTPAuthorizationCredentials = Depends(bearer_security),
-    db: Session = Depends(get_session),
+    # NOTE: We intentionally do NOT use Depends(get_session) here.
+    # Sessions are managed internally with short-lived context managers.
+    # This ensures connections are released immediately after auth queries,
+    # not held for the entire request duration (e.g., during 30+ second LLM calls).
 ):
     token = None
 
@@ -294,7 +295,7 @@ async def get_current_user(
 
     # auth by api key
     if token.startswith("sk-"):
-        user = get_current_user_by_api_key(request, token, db=db)
+        user = get_current_user_by_api_key(request, token)
 
         # Add user info to current span
         current_span = trace.get_current_span()
@@ -323,7 +324,7 @@ async def get_current_user(
                     detail="Invalid token",
                 )
 
-            user = Users.get_user_by_id(data["id"], db=db)
+            user = Users.get_user_by_id(data["id"])
             if user is None:
                 raise HTTPException(
                     status_code=status.HTTP_401_UNAUTHORIZED,
@@ -373,8 +374,9 @@ async def get_current_user(
         raise e
 
 
-def get_current_user_by_api_key(request, api_key: str, db: Session = None):
+def get_current_user_by_api_key(request, api_key: str):
-    user = Users.get_user_by_api_key(api_key, db=db)
+    # Each function call manages its own short-lived session internally
+    user = Users.get_user_by_api_key(api_key)
 
     if user is None:
         raise HTTPException(
@@ -402,7 +404,7 @@ def get_current_user_by_api_key(request, api_key: str, db: Session = None):
         current_span.set_attribute("client.user.role", user.role)
         current_span.set_attribute("client.auth.type", "api_key")
 
-    Users.update_last_active_by_id(user.id, db=db)
+    Users.update_last_active_by_id(user.id)
     return user