[#102652] [Ruby master Bug#17664] Behavior of sockets changed in Ruby 3.0 to non-blocking — ciconia@...
Issue #17664 has been reported by ciconia (Sharon Rosner).
23 messages
2021/02/28
[ruby-core:102546] [Ruby master Feature#17592] Ractor should allowing reading shareable class instance variables
From:
marcandre-ruby-core@...
Date:
2021-02-16 20:29:11 UTC
List:
ruby-core #102546
Issue #17592 has been updated by marcandre (Marc-Andre Lafortune).
ko1 (Koichi Sasada) wrote in #note-13:
> (2) Performance concern
>
> To allow accessing ivars from other ractors, every ivar accesses to class/module should be synchronized.
I am surprised this is the case. Would it not be possible to have overwriting an existing instance variable be a single memory write operation? Adding a new instance variable would similarly involve creating a new ivar table and setting it with a single memory write operation?
> Current implementation doesn't need to synchronize this accesses.
That is not completely accurate. Current implementation does not but it is not 100% safe. The following completely artificial code crashes (sometimes):
```ruby
class String
def self.test
4000.times.map { |i| eval(<<~RUBY) }.each(&:join)
Thread.new do
10.times do
Thread.pass
@x#{i} = 42
end
end
RUBY
end
end
String.test
p String.instance_variables.size # => 4000
```
----------------------------------------
Feature #17592: Ractor should allowing reading shareable class instance variables
https://bugs.ruby-lang.org/issues/17592#change-90447
* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
----------------------------------------
It would be very helpful if Ractor was allowing reading class instance variables from non-main Ractor.
Currently is raises an IsolationError:
```ruby
module Foo
singleton_class.attr_accessor :config
Foo.config = {example: 42}.freeze
end
Ractor.new { p Foo.config } # => IsolationError
```
This limitation makes it challenging to have an efficient way to store general configs, i.e. global data that mutated a few times when resources get loaded but it immutable afterwards, and needs to be read all the time.
Currently the only way to do this is to use a constant and use `remove_const` + `const_set` (which can not be made atomic easily).
I think that allowing reading only may be the best solution to avoid any race condition, e.g. two different Ractors that call `@counter += 1`.
The only 3 scenarios I see here are:
0) declare the constant hack the official way to store config-style data
1) allow reading of instance variables for shareable objects (as long as the data is shareable)
2) allow read-write
I prefer 1)
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