Stale sessions from a stolen device could be reused up to the cache
TTL after a legitimate user re-logs in, because login never cleared
the existing cache entry.
Changes:
- Add invalidate_by_user(user_id) to SessionCache protocol
- InMemorySessionCache maintains a user_id -> set[token] index to
support O(1) invalidation of all sessions for a given user
- NoOpSessionCache stub updated for API compatibility
- auth_service.login() now returns the Session object alongside
signed_token and expires_at
- login router calls session_cache.invalidate_by_user(session.id)
immediately after successful authentication
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Addresses: Backend session cache not cluster-safe (multi-worker issue)
Problem:
- Session cache is process-local (InMemorySessionCache)
- Multi-worker deployments (uvicorn --workers N) create separate processes
- Each process has its own independent session cache
- Sessions cached in Worker A are invisible to Workers B, C, D
- Users randomly logged out when requests land on different workers
- Also affects RuntimeState, rate limiter, and background jobs
Solution (Option A - Strict single-worker enforcement):
- Enhance startup validation with clearer error messages
- Update error messages to explain the problem and how to fix it
- Document single-worker requirement prominently in Docker configs
- Update module docstrings to clarify constraints
Changes:
1. app/startup.py:
- Enhanced _check_single_worker_mode() error message with troubleshooting
- Enhanced _stage_check_worker_mode_and_acquire_lock() error message
- Removed unused import
2. app/utils/session_cache.py:
- Updated module docstring to explain constraints more clearly
- Added references to deployment documentation
- Clarified multi-worker solution for future implementation
3. app/utils/runtime_state.py:
- Updated module docstring with deployment constraint references
- Aligned messaging with session_cache.py
4. Docker/Dockerfile.backend:
- Added comprehensive comments about single-worker requirement
- Explained impact in multi-worker deployments
- Referenced deployment constraints documentation
5. Docker/docker-compose.yml, compose.prod.yml, compose.debug.yml:
- Added documentation comments about BANGUI_WORKERS constraint
- Explained why single-worker is required
6. backend/tests/test_startup_integration.py:
- Fixed test unpacking to match function return signature (3 values, not 2)
This ensures multi-worker deployments fail loudly at startup with clear
guidance on what went wrong and how to fix it. The database-backed scheduler
lock provides defense-in-depth for container orchestration scenarios.
For future multi-worker support, implement:
- Redis or database-backed session cache
- Shared RuntimeState coordination
- Distributed APScheduler backend
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
- Add comprehensive docstring to runtime_state.py explaining single-process
constraint, impacts in multi-worker deployments, and solution approach
- Add comprehensive docstring to session_cache.py explaining process-local
cache limitation, security implications, and Redis/database alternatives
- Update Architecture.md to clarify session cache is process-local and
describe single-worker enforcement via TASK-002
- Update Architecture.md runtime state section with detailed explanation of
per-process state and multi-worker impacts
- Add Backend-Development.md section 13.7.2 documenting session cache
pluggability pattern with example Redis implementation
- All tests pass; linting passes; type checking has pre-existing errors
This is the short-term fix for TASK-003: enforce single-worker deployment
(TASK-002) and document the constraint clearly. The long-term fix (Redis
backend) is deferred as a follow-up.
Use NoOpSessionCache in backend/app/main.py and dynamically switch cache implementation in backend/app/dependencies.py so disabled cache mode remains safe while get_session_cache always returns a valid object.
