From: "ivoanjo (Ivo Anjo) via ruby-core" <ruby-core@...>
Date: 2023-08-25T08:12:02+00:00
Subject: [ruby-core:114528] [Ruby master Feature#17678] Ractors do not restart after fork

Issue #17678 has been updated by ivoanjo (Ivo Anjo).





> 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.



Thanks for looking into this!



I don't think the info is there in #inspect... At least I don't get it on stable or latest ruby-head? ����



Here's an updated example:



```ruby

puts RUBY_DESCRIPTION



r2 = Ractor.new { puts "[#{Process.pid}] Ractor started!"; sleep(1000) }



puts "[#{Process.pid}] In parent process, ractor status is #{r2.inspect}"



sleep(1)

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



fork do

  puts "[#{Process.pid}] In child process, ractor status is #{r2.inspect}"

end



Process.wait

```



and here's what I get:



```

$ ruby ractor-test.rb

ruby 3.3.0dev (2023-08-24T12:12:51Z master 5ec1fc52c1) [x86_64-linux]

ractor-test.rb:3: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.

[10] In parent process, ractor status is #<Ractor:#2 ractor-test.rb:3 blocking>

[10] Ractor started!

[10] Forking...

[12] In child process, ractor status is #<Ractor:#2 ractor-test.rb:3 blocking>

```



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

Feature #17678: Ractors do not restart after fork

https://bugs.ruby-lang.org/issues/17678#change-104327



* 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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