Bug #17203
closedLogger::Formatter won't work with non main Ractor
Description
class Rogger < Ractor
def self.new
super do
# STDOUT cannot be referenced but $stdout can
logger = ::Logger.new($stdout)
# Run the requested operations on our logger instance
while data = recv
logger.public_send(data[0], *data[1])
end
end
end
# Really cheap logger API :)
def method_missing(m, *args, &_block)
self << [m, *args]
end
end
class Rails
LOGGER = Rogger.new
def self.logger
LOGGER
end
end
Ractor.new do
Rails.logger.info "Hello"
end
running this ends up with:
terminated with exception (report_on_exception is true):
ruby/3.0.0/logger/formatter.rb:15:in `call': can not access global variables $$ from non-main Ractors (RuntimeError)
from ruby/3.0.0/logger.rb:586:in `format_message'
from ruby/3.0.0/logger.rb:476:in `add'
from ruby/3.0.0/logger.rb:529:in `info'
from test.rb:23:in `public_send'
from test.rb:23:in `block in new'
however the same with fixed formatter works.
PR: https://github.com/ruby/ruby/pull/3600
All of the code examples are here: https://mensfeld.pl/2020/09/building-a-ractor-based-logger-that-will-work-with-non-ractor-compatible-code/
Updated by Eregon (Benoit Daloze) over 3 years ago
- Assignee set to ko1 (Koichi Sasada)
Since $$
returns a (read-only) Integer, it seems harmless to let Ractors read it.
Although I think Process.pid
is nicer than $$
:)
$stdout
OTOH should not be possible to access from non-main Ractor, no matter the access path.
It's a mutable object, if it's shared between Ractors it can lead to segfaults.
Updated by Eregon (Benoit Daloze) over 3 years ago
I tried to make an example why sharing a mutable object is problematic, but I think I just got more confused :D
ruby -e '$stdout.instance_variable_set(:@private, Object.new); p $stdout.object_id; p $stdout.instance_variables; Ractor.new { p $stdout.object_id; p $stdout.instance_variables; p $ $stdout.instance_variable_get(:@private) }.take'
60
[:@private]
<internal:ractor>:38: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
80
[]
nil
So $stdout
in each Ractor is a different object?
Might be a good way to still let p/print/puts
work in Ractors.
The $stdout variable is Ractor-local, so that might make sense.
This sometimes trigger a [BUG]:
$ ruby -e 'p $stdout.object_id; 10.times.map { Ractor.new { p $stdout.object_id } }; sleep 1'
60
<internal:ractor>:38: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
80
100
120
140
160
180220200
240
260
-e: [BUG] Object ID seen, but not in mapping table: 0x000055a75f933080 [0 U] T_ZOMBIE
ruby 3.0.0dev (2020-09-29T15:32:22Z master c38605de6b) [x86_64-linux]
-- Control frame information -----------------------------------------------
c:0001 p:0000 s:0003 E:000b10 (none) [FINISH]
-- C level backtrace information -------------------------------------------
[0x55a75e3b5c6e]
/home/eregon/prefix/ruby-master/bin/ruby(rb_bug+0xe5) [0x55a75e1be426] error.c:723
/home/eregon/prefix/ruby-master/bin/ruby(obj_free_object_id+0x19) [0x55a75e1e9fe8] gc.c:2691
/home/eregon/prefix/ruby-master/bin/ruby(finalize_list) gc.c:2679
[0x55a75e1ee213]
/home/eregon/prefix/ruby-master/bin/ruby(rb_ec_cleanup+0x2e8) [0x55a75e1cf558] eval.c:173
[0x55a75e1cfcc1]
/home/eregon/prefix/ruby-master/bin/ruby(main+0x6f) [0x55a75e1c32ef] ./main.c:50
Updated by ko1 (Koichi Sasada) over 3 years ago
Eregon (Benoit Daloze) wrote in #note-1:
Since
$$
returns a (read-only) Integer, it seems harmless to let Ractors read it.
I agree. it should be read from any ractors.
Updated by Eregon (Benoit Daloze) over 3 years ago
- Status changed from Open to Closed
The PR was merged, and $$
can be accessed from Ractors in #17268, I think we can close this.