[ruby-core:118456] [Ruby master Bug#20413] Enumerator can block fiber scheduler.
From:
"nagachika (Tomoyuki Chikanaga) via ruby-core" <ruby-core@...>
Date:
2024-07-06 02:24:43 UTC
List:
ruby-core #118456
Issue #20413 has been updated by nagachika (Tomoyuki Chikanaga).
Backport changed from 3.0: UNKNOWN, 3.1: REQUIRED, 3.2: REQUIRED, 3.3: DONE to 3.0: UNKNOWN, 3.1: REQUIRED, 3.2: DONE, 3.3: DONE
Sorry, I accidentally handled a different ticket (#20414).
ruby_3_2 commit:2f8f17e842666abb05ca522d6072c957fab0e12e merged revision(s) commit:5d1702e01a36e11b183fe29ce10780a9b1a41cf0.
----------------------------------------
Bug #20413: Enumerator can block fiber scheduler.
https://bugs.ruby-lang.org/issues/20413#change-108970
* Author: ioquatix (Samuel Williams)
* Status: Closed
* Assignee: ioquatix (Samuel Williams)
* Backport: 3.0: UNKNOWN, 3.1: REQUIRED, 3.2: DONE, 3.3: DONE
----------------------------------------
Using `Enumerator` in the event loop can cause problems as the fiber created by `rb_fiber_new` is blocking by default. It should be non-blocking.
```ruby
#!/usr/bin/env ruby
require 'async'
Async do
Async do
while true
puts "Hello"
sleep 1
end
end
enumerator = Enumerator.new do |yielder|
while true
yielder << "World"
sleep 1
end
end
while true
puts enumerator.next
end
end
```
Before this PR, the output is:
```
> ./test.rb
Hello
World
World
World
World
World
World
...
```
After this PR, the output is:
```
> ./test.rb
Hello
World
Hello
World
Hello
World
Hello
World
Hello
World
...
```
The reason why this happens, is because the enumerator `sleep` never yields to the event loop.
See <https://github.com/ruby/ruby/pull/10481> for the fix.
--
https://bugs.ruby-lang.org/
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