From: "headius (Charles Nutter)" <noreply@...>
Date: 2021-10-07T12:56:12+00:00
Subject: [ruby-core:105588] [Ruby master Feature#17849] Fix Timeout.timeout so that it can be used in threaded Web servers

Issue #17849 has been updated by headius (Charles Nutter).


mame (Yusuke Endoh) wrote in #note-14:
> Just FYI. According to @ko1, masking all exceptions in an ensure clause is possible in pure Ruby, as long as you use MRI.
> 
> ```
> begin
>   ...
> ensure
>   Thread.handle_interrupt(Object => :never) do
>     ..
>   end
> end
> ```

This is incorrect code. The `handle_interrupt` code must go outside of the entire begin/ensure/end block or you still run the risk of being interrupted before the ensure runs.

`handle_interrupt` is a band-aid over the real problem, which is that code can be interrupted at any time. Unfortunately the Ruby Way to fix this is that users have to **opt in** to get safe ensures, and almost nobody gets it right. Every library in existence is broken.

And for the record, both JRuby and TruffleRuby fully support `handle_interrupt`, so you don't have to use MRI.

```
Thread.handle_interrupt(Object => :never) do
  begin
    Thread.handle_interrupt(Object => :immediate) do
      ...
    end
  ensure
    ...
  end
end
```

See http://blog.headius.com/2008/02/ruby-threadraise-threadkill-timeoutrb.html

`handle_interrupt` makes it possible to avoid some of these problems, but nobody is using it and the ones who are using it are using it wrong.

----------------------------------------
Feature #17849: Fix Timeout.timeout so that it can be used in threaded Web servers
https://bugs.ruby-lang.org/issues/17849#change-94056

* Author: duerst (Martin D��rst)
* Status: Open
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
----------------------------------------
Making this a separate issue from #17837

Eregon (Benoit Daloze) wrote in https://bugs.ruby-lang.org/issues/17837#note-10 (which is  about timeouts for regular expressions):

> I think fixing Timeout.timeout might be possible.
> The main/major issue is it can trigger within `ensure`, right? Is there anything else?
> We could automatically mask `Thread#raise` within `ensure` so it only happens after the `ensure` body completes.
> And we could still have a larger "hard timeout" if an `ensure` takes way too long (shouldn't happen, but one cannot be sure).
> I recall discussing this with @schneems some time ago on Twitter.





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