[agustin18]

What is this project?

fastapi-stream-lease is an async concurrency lease manager for long-lived streaming endpoints (SSE, WebSockets, and LLM chat completions) in FastAPI and Starlette.

Why is it awesome?

• Solves the active connection problem: standard token-bucket limiters count requests per minute, which fails when an SSE completion stays open for 30–60 seconds. fastapi-stream-lease tracks active open connections in real time across workers using Redis sorted sets and atomic Lua CAS.
• Guaranteed resource cleanup: immediately releases concurrency slots when downstream clients disconnect (aclose cancellation), preventing orphaned background generation.
• Production readiness: 100.00% statement and branch test coverage, multi-version CI (Python 3.10–3.13), Redis Sentinel and Cluster failover protection, and Prometheus/OpenTelemetry metrics.
• Published on PyPI (pip install fastapi-stream-lease) under the MIT license.