Is waiting on multiple channels with tokio::select! can skip messages or not?

[sushi-shi]

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By select! documentation it is stated, that it waits for the first future to succeed and drops all other futures. And I wonder whether waiting on multiple receivers with poll in a loop is safe, or I might loose some messages because of it (i.e. whether waiting on a receiver is cancellation safe).

[h3nill]

Do you mean calling eventloop.poll on multiple branches of select!?

I think it would be easier to answer if you can provide more context on whats your usecase for it.

[tekjar]

@sushi-shi We'll check and get back to you cancellation safety

[dlips]

Hi, did you come to a conclusion if the future returned by .poll() is cancellation safe? I would use poll() with tokio::select! if it is. Reviewing the code, I think the critical part is in Eventloop::select(). Because this function uses select! internally, I assume that each branch there should be cancel safe, meaning that the whole Eventloop::select() function is cancel safe. Am I right? Would be nice to add this to the documentation of Eventloop::poll()

[rtumac]

I would also like to know if .poll() on an EventLoop instance is cancel safe. Thanks!