Create Loom-friendly concurrent weak set (FiberSet)

[jdegoes]

At various points in ZIO, we need the ability to hold onto a set or bag of fibers. We need the ability to concurrently add and remove items from this set / bag, without synchronization or other locks. Finally, we need concurrent (and eventually consistent) iteration over this set / bag.

Ensuring there are no duplicates is not really important, nor does it ever happen, so the "set" aspect of this need not be enforced, which can potentially lead to a more efficient implementation.

Finally, weak references are slow. It would be nice to avoid them entirely, but that's not possible since some fibers are suspended forever and do not shut down cleanly, so garbage collection is necessary to preserve.

However, it's possible using reference queue or other techniques, we could reduce the number of weak refs we create.

This ticket is for implementation of such a high-performance structure, benchmarks showing superior performance, and comprehensive test suite; together with incorporating this weak concurrent set into the Fiber children set, and the set of root fibers.

[jdegoes]

/bounty $1500

[algora-pbc]

💎 $1,500 bounty • ZIO

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1. Start working: Comment /attempt #8861 with your implementation plan
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Attempt	Started (GMT+0)	Solution
🔴 @kyri-petrou	May 16, 2024, 10:48:18 AM	WIP
🔴 @snigdha510	May 17, 2024, 6:35:18 AM	WIP

[jdegoes]

cc @kyri-petrou

[kyri-petrou]

/attempt #8861

Got an approach in mind that's looking feasible so far. If all goes well I'm hoping to have a draft PR for it next week

Algora profile	Completed bounties	Tech	Active attempts	Options
@kyri-petrou	9 ZIO bounties	Scala, Python, Shell & more		Cancel attempt

[snigdha510]

/attempt #8861

Options

• Cancel my attempt

[algora-pbc]

Note

The user @kyri-petrou is already attempting to complete issue #8861 and claim the bounty. We recommend checking in on @kyri-petrou's progress, and potentially collaborating, before starting a new solution.

[algora-pbc]

@kyri-petrou: Reminder that in 7 days the bounty will become up for grabs, so please submit a pull request before then 🙏

[algora-pbc]

@snigdha510: Reminder that in 7 days the bounty will become up for grabs, so please submit a pull request before then 🙏

[algora-pbc]

The bounty is up for grabs! Everyone is welcome to /attempt #8861 🙌