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coolio
coolio

Reputation: 41

Python asyncio: Do I Need Synchronization Primitives for Shared Variables When Using run_in_executor with ThreadPoolExecutor?

I'm working with Python's asyncio and triing to understand the run_in_executor function with the default ThreadPoolExecutor to handle blocking tasks asynchronously. My concern is regarding accessing shared variables within these tasks.

My understanding is: When I use run_in_executor with a ThreadPoolExecutor, the tasks are executed in separate threads. Therefore, to ensure thread safety and prevent race conditions, I should use synchronization primitives like locks when accessing shared variables, just as I would with the threading module.

Is my understanding correct, or does asyncio handle shared variables differently in this context?

Upvotes: 0

Views: 69

Answers (1)

Ilya Egorov
Ilya Egorov

Reputation: 251

Yes, your understanding is correct. A thread with asyncio event loop is a normal thread that races equally with other threads. Also, threads started via run_in_executor() have no special semantics, and this method just comes as a wrapper so that you can asynchronously get a result (or exception) after the thread executes. But there are some points to consider:

  • If shared state is only accessed by threads executing synchronous functions, feel free to use primitives from the threading module.
  • If shared state is also accessed by asynchronous functions, you may need thread-safe primitives that do not block the event loop so that asynchronous tasks can still run concurrently.

However, note that in a free-threaded mode, threads can be executed in true parallel. This is why you should not use primitives from the threading module unless you are sure that the lock will be held for a very short time: you can thus limit the concurrency of asynchronous tasks.

Upvotes: 0

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