[ruby-core:100841] [Ruby master Feature#17322] Deprecate `Random::DEFAULT` and introduce `Random.default()` method to provide Ractor-supported default random generator

Issue #17322 has been updated by Dan0042 (Daniel DeLorme).


Eregon (Benoit Daloze) wrote in #note-6:
> I think `rand`, etc should use a thread-local Random instance (and thread-local implies Ractor-local, of course).
> Those thread-local Random instances should probably not be exposed to the Ruby level, so that way there is never a need to synchronize access to it.

Bypassing the need for synchronization is a very good idea.

> Is there any case where it's useful?

Good question. Found this. Doesn't look so useful.

    faker-2.2.2/lib/faker.rb
    35:        @random || Random::DEFAULT
    
    sentry-raven-2.11.1/lib/raven/configuration.rb
    445:      if Random::DEFAULT.rand >= sample_rate

That said, even though using Random::DEFAULT seems like an anti-pattern, there's no real benefit to removing it. Maybe just convert it to an instance not used by anything? (except gems/apps)

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Feature #17322: Deprecate `Random::DEFAULT` and introduce `Random.default()` method to provide Ractor-supported default random generator
https://bugs.ruby-lang.org/issues/17322#change-88483

* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
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`Random::DEFAULT` a default random generator used by `rand`, `srand`, `Array#shuffle` without a given random generator, and so on.

Random generators are not thread-safe, so they are not ractor safe, and they are not shareable.
So a program refer to `Random::DEFAULT` on non-main ractor, it causes an error.

To provide per-ractor default random generator, this ticket propose the `Random.default()` method which returns per-ractor random generator.
`Random::DEFAULT` is a result of `Random.default()` on main-ractor and it should be deprecated, or at least it should not be used on multi-ractor supporting apps and libraries.





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