Add ability to reset timers.

[macournoyer]

I need to be able to change the timeout during a Fiber.scheduler.with_timeout block.

Types of Changes

• New feature.

Contribution

• I added tests for my changes.
• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.

[macournoyer]

Will add some tests if that proposal make sense.

[ioquatix]

In principle, I understand the use case and agree a bit more flexibility here could be useful - we actually had this previously in the timers gem - but I decided to optimise the implementation and reduce flexibility since the most common use case doesn't adjust the timeout.

Unfortunately, the proposed change is insufficient - it is not that simple to modify the timer handles, as they are effectively immutable - they may get inserted into a heap. It is tricky to evict them from the heap (since we don't know where they are), so instead when we pop handles out of the heap, we check whether they were cancelled before executing them.

As such, changing an existing handle beyond cancellation is not supported.

So, how to implement the proposed feature without a big cost?

We could expand the implementation here, but then every single timer would pay the cost despite the flexibility not being used much.

Therefore, I don't think we should modify this code, and instead, if the timeout needs to be extended, we can do that by cancelling a handle and scheduling a new handle. Here is an implementation: socketry/async#386 - we only use this interface if the user asks for it - so the existing use cases don't have any extra object allocations or overheads.

[samuel-williams-shopify]

See https://github.com/socketry/timers/blob/23bccc713a244a339500318616fae79d9922a78f/lib/timers/timer.rb#L34-L93 for the timers gem code - as you can see, it's significantly more complex than the current implementation of Handle. Yet, we can implement most of the functionality on top of Handle efficiently.