[Data] Close threads from async UDF after actor died #59261
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owenowenisme
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Code Review
This pull request addresses an issue where asyncio threads in async UDFs could prevent actor processes from shutting down correctly. The proposed fix of setting daemon=True when creating the thread is the correct and standard approach to ensure that these background threads do not block the main process from exiting. The change is concise, well-targeted, and effectively resolves the described problem.
alexeykudinkin
approved these changes
Dec 9, 2025
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Description
When using async map with actors in Ray Data, the asyncio thread can keep the actor process alive and block shutdown even after the actor is marked as dead. This occurs because the asyncio thread does not exit when the main thread finishes.
To fix this, we create the thread with
daemon=True, ensuring it terminates when the main thread exits.Related issues
Closes #59033