MemRelay/projects/d5a7f581-c442-4554-87b9-ee723b8b0258/坑：FastAPI async def 里阻塞 I-O 冻结事件循环.md

title, type, permalink, stable_id, scope, project_id, memory_type, status, revision, restored_from_commit, created_at, updated_at, tags

title	type	permalink	stable_id	scope	project_id	memory_type	status	revision	restored_from_commit	created_at	updated_at	tags
坑：FastAPI async def 里阻塞 I/O 冻结事件循环	experience	main/projects/d5a7f581-c442-4554-87b9-ee723b8b0258/坑-fast-api-async-def-里阻塞-i-o-冻结事件循环	df065dbf-85de-4f2b-bbb1-5d8b115de08c	project	d5a7f581-c442-4554-87b9-ee723b8b0258	experience	active	1	6a6a895eaf	2026-09-23T15:09:57.195425+00:00	2026-09-23T15:09:57.195491+00:00	pitfall fastapi async

CapacityReport 大表导出把 /health 都卡死：async def 处理函数里直接调 pymysql/大文件/轮询等阻塞 I/O，事件循环被占满。修复：把这类处理函数改成普通 def，FastAPI 自动扔进线程池。通用经验：同步库（pymysql、paramiko、requests）的调用链不要包在 async def 接口里；另外重建线程池时旧池用 shutdown(wait=False) 非阻塞关闭（database/jobs.py、scripts/runs.py 的 _pool 模式）。