[ruby-core:101378] [Ruby master Feature#17363] Timeouts

Issue #17363 has been updated by marcandre (Marc-Andre Lafortune).


ko1 (Koichi Sasada) wrote in #note-4:
> I also positive to introduce `timeout` but not sure what happens on timeout.
> 
> * raise an exception -> which exception?

How about subclassing `Timeout::Error` to create `Queue::Timeout` and `Ractor::Timeout`?

> * return `nil` -> can't recognize returned value

Agreed, it is not a good solution.

> I think `timeout: nil` is same as no `timeout:` given. Is it same as other methods?

Agree.

I think `queue.pop(timeout: 0)` should be same as `queue.pop(true)` but raise `Queue:Timeout`.

Same idea with Ractor, `timeout: 0` is non-blocking version of `Ractor.receive/receive_if/select`.


----------------------------------------
Feature #17363: Timeouts
https://bugs.ruby-lang.org/issues/17363#change-89137

* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
----------------------------------------
Builtin methods like `Queue.pop` and `Ractor.receive` have no timeout parameter.

We should either:
- provide such a parameter
- and/or provide a `Timeout::wake` that raises an timeout error only if the block is currently sleeping.

Details:

```ruby
q = Queue.new
# ...
elem = Timeout::timeout(42) { q.pop } # => It is possible that an element is retreived from the queue but never stored in `elem`

elem = Timeout::wake(42) { q.pop } # => Guaranteed that either element is retrieved from the queue or an exception is raised, never both
Timeout::wake(42) { loop {} } # => infinite loop
# and/or
elem = q.pop(timeout: 42)
```

Currently, the only reliable way to have a Queue that accepts a timeout is to re-implement it from scratch. This post describe how involved that can be: https://spin.atomicobject.com/2017/06/28/queue-pop-with-timeout-fixed/



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