Ephemeral threads

[Robert Engels]

I think ClosableQueue - which are essentially CSP channels - demonstrates that you don’t need anything special to accomplish this with the existing infrastructure with loom or structured concurrency.

> On Jan 10, 2026, at 11:18 AM, Alan Bateman <Alan.Bateman at oracle.com> wrote:
> 
> On 10/01/2026 16:00, Andrew Haley wrote:
>> 
>> OK, I think I get it. The issue here is that a thread is unreachable but can be resurrected if it's finalized.
>> 
>> So, at some risk of flogging a dead horse, I'm wondering: what if we could figure out a way in which an unreachable thread could be GC'd, but only if it was honest-to-goodness unreachable, i.e. it wasn't on a reference queue and it had no finalizer. We'd be good, right?
>> 
> Hopefully finalization will be disabled by default, and eventually removed, but there a lot more to the topic. You can summon other demons when the threads act on objects with cleaners (or more generally, anything with cleanup actions based on phantom refs). This can lead to cleaning actions that attempt to release resources in an inconsistent state. Even if we spent a few years on the issues, the usage (to allow the alive threads be GC'ed) is very fragile to setup, and the resulting behavior would surely be surprising to most developers. If we do channels that integrate with structured concurrency then it might be that some of the calls for ephemeral threads go away.
> 
> -Alan.