feat: add configurable behavior for cancelled get() calls

[Sh4d1]

Fixes #16

When pool.get() is cancelled (via a tokio::time::timeout for instance) while is_recyclable() is running, the object being validated is unconditionally detached from the pool.

This patch introduces a CancellationBehavior option:

• Detach (default): Detach the object from the pool. This preserves existing behavior.
• ReturnToPool: Return the object to the pool for potential reuse.

cc @tisonkun

[tisonkun]

Thanks for your contribution @Sh4d1!

The ReturnToPool impl looks really good.

I'm considering always returning the unready object to the pool if is_recyclable is cancelled, since it does no harm the next get would check is_recyclable again.

In this way, we expose less config options to users and reduce the learning burden. I think the most proper manner here is to return the unready_object to the pool.

We may further merge UnreadyObject and Object.

What do you think?

[Sh4d1]

I thought about it, but it really depends on the behaviour of is_recyclable. For my usecase it works, but I was unsure of all the usecase behind it so added it that way to not break anyone's setup!

If you think it's better to return to the pool everytime we can change to that behaviour 😄

[tisonkun]

on the behaviour of is_recyclable

Ah. Correct. Since is_recyclable takes &mut Self::Object, the state can be modified and in an intermediate unready state.

Let's keep the current structure and I'll merge it in this week (ping me if I fail to merge it).

The very last concern from my side is about naming and docs. CancellationBehavior reads too generic but I can't find a better one now.

[Sh4d1]

Yeah I also find the naming a bit generic but couldn't find something else without having like DropBehaviourOnGet which is a bit of a mouthful 😅

[tisonkun]

@Sh4d1 I chose RecycleCancelledStrategy to be precise and aligned with QueueStrategy naming.

If you're OK with this, I'm going to merge this patch and release a 1.1.0 version to deliever it :D

[Sh4d1]

Perfect ! Works for me 😄 thanks @tisonkun !

[tisonkun]

@Sh4d1 v1.1.0 has been released with this feature included. Feel free to test it out and I'd appreciate it if you can give the feedback :D

[Sh4d1]

Yay! I'll try to bump it next week on our side !