[ruby-core:111850] [Ruby master Feature#19333] Setting (Fiber Local|Thread Local|Fiber Storage) to nil should delete value in order to avoid memory leaks.

Issue #19333 has been updated by Eregon (Benoit Daloze).


There are some, yes, see https://github.com/search?q=%22Thread.current%5B%22+%22%5D+%3D+nil%22+language%3ARuby&type=code&l=Ruby
Some are about cleaning after usage in `ensure`, but not all.
And even then it's not clear if it's never used again after.
For example I saw a `= nil` to reset a connection.

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Feature #19333: Setting (Fiber Local|Thread Local|Fiber Storage) to nil should delete value in order to avoid memory leaks.
https://bugs.ruby-lang.org/issues/19333#change-101262

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
As it stands, Fiber Locals, Thread Locals and Fiber Storage have no way of deleting key-value associations.

```ruby
100.times do |i|
  name = :"variable-#{i}"
  Thread.current[name] = 10
end
```

Because of this, dynamically generated associations can leak over time. This is worse for things like Threads that might be pooled (or maybe an argument against user-space pooling).

In any case, having a way to delete those associations would allow application code to at least delete the associations when they no longer make sense.

I propose that assigning `nil` to "locals" or "storage" should effectively delete them.

e.g.

```ruby
100.times do |i|
  name = :"variable-#{i}"
  Thread.current[name] = 10
  Thread.current[name] = nil # delete association
end
```

A more invasive alternative would be to define new interfaces like `Thread::Local`, `Fiber::Local` and `Fiber::Storage::Local` (or something) which correctly clean up on GC.



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