CODEWITHSUNDEEP
pythonthread-safetypython-asyncio
Richard Levasseur
Richard Levasseur

Reputation: 14882

Is asyncio's loop.run_in_executor thread-safe?

I'm trying out asyncio and have to mix it with some normal multi threaded blocking code, so I need to offload the execution using run_in_exector.

The asyncio docs warn that "most functions" aren't threadsafe, and that call_soon_threadsafe is the only thread-safe function. There are a couple others, like Future.add_done_callback, too, that are explicitly documented as thread safe. It then has a sentence afterwards saying "you can use run_in_executor to run callbacks in other threads", but doesn't comment on the thread-safety of it specifically.

run_in_executor isn't doc'd to be thread-safe, but looking at the source, it looks like it is thread safe if the right code-paths are taken.

Does anyone know if it is supposed to be thread safe, but just isn't documented to be that way?

Upvotes: 12

Views: 3542

Answers (3)

vstinner
vstinner

Reputation: 1404

The default implementation looks to be thread-safe if the executor parameter is not None or the default executor is already set (call loop.set_default_executor()). Otherwise, two executor may be created.

You may write a patch to make the method thread-safe ;-)

Upvotes: 3

Andrew Svetlov
Andrew Svetlov

Reputation: 17366

run_in_executor is supposed to be not threadsafe by specification (sorry, it looks like implicit statement and probably should be clarified in PEP-3156).

Even if concrete implementation is thread safe please don't assume that any PEP-3156 compliant implementation will be thread-safe too.

Upvotes: 7

leech
leech

Reputation: 8421

I think it entirely depends on what you give it. It effectively just starts a thread and runs your code, so whether that is thread safe or not depends on what you tell it to do.

Upvotes: 3

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