From: "jeremyevans0 (Jeremy Evans) via ruby-core" <ruby-core@...>
Date: 2023-08-24T21:12:01+00:00
Subject: [ruby-core:114513] [Ruby master Feature#17678] Ractors do not restart after fork

Issue #17678 has been updated by jeremyevans0 (Jeremy Evans).



Tracker changed from Bug to Feature

ruby -v deleted (ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-linux])

Backport deleted (2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN)



As Ractors always use separate OS threads, and fork only runs the current thread in the forked process, I don't see a way for Ractors to continue where they left off after fork.  I think auto-starting would likely be a bad idea, because auto-starting would not return them to the state they were at fork.



The addition of `Ractor#alive?` and/or `Ractor#status` makes sense to me. Even in non-forked processes such methods could be useful.  Note that you can get what you want already, by calling `Ractor#inspect`, so these methods would only need to expose information that Ractor is already storing.



----------------------------------------

Feature #17678: Ractors do not restart after fork

https://bugs.ruby-lang.org/issues/17678#change-104304



* Author: ivoanjo (Ivo Anjo)

* Status: Assigned

* Priority: Normal

* Assignee: ko1 (Koichi Sasada)

----------------------------------------

Hello there! I'm working at Datadog on the `ddtrace` gem -- <https://github.com/DataDog/dd-trace-rb> and we're experimenting with using Ractors in our library but run into a few issues.



### Background



When running a Ractor as a background process, the Ractor stops & does not restart when the application forks.



### How to reproduce (Ruby version & script)



`ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-linux]`



```ruby

r2 = Ractor.new do

 loop { puts "[#{Process.pid}] Ractor"; sleep(1) }

end

 

sleep(1)

puts "[#{Process.pid}] Forking..."

 

fork do

 sleep(5)

 puts "[#{Process.pid}] End fork."

end

 

loop do

 sleep(1)

end

```



### Expectation and result



The application prints ���Ractor��� each second in the main process, but not in the fork.



Expected the Ractor (defined as `r2`) to run in the fork.



```

[29] Ractor

[29] Ractor

[29] Forking...

[29] Ractor

[29] Ractor

[29] Ractor

[29] Ractor

[29] Ractor

[32] End fork.

[29] Ractor

[29] Ractor

[29] Ractor

```



### Additional notes



Threads do not restart across forks either, so it might not be unreasonable to expect consistent behavior. However, it���s possible to detect a dead Thread and recreate it after a fork (e.g. with `#alive?`, `#status`), but there���s no such mechanism for Ractors.



### Suggested solutions



1. Auto-restart Ractors after fork

2. Add additional methods to Ractors that allow users to check & manage the status of the Ractor, similar to Thread.







-- 

https://bugs.ruby-lang.org/

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