Issue #6647 has been updated by nahi (Hiroshi Nakamura).

Category set to core
Status changed from Open to Assigned
Assignee set to matz (Yukihiro Matsumoto)
Target version set to 2.0.0

Discussions ad CRuby dev meeting at 14th July.

 * We can understand the requirement. (We understood that the requirement is dumping something without raising when Thread#abort_on_exception = false)
 * Writing to STDERR could cause problem with existing applications so we should take care about it.
 * rb_warn() instead of puts would be good because we already using rb_warns.

Matz, do you mind if we dump Thread error with rb_warn if Thread#abort_on_exception = false?
----------------------------------------
Bug #6647: Exceptions raised in threads should be logged
https://bugs.ruby-lang.org/issues/6647#change-28068

Author: headius (Charles Nutter)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: 2.0.0
ruby -v: head


Many applications and users I have dealt with have run into bugs due to Ruby's behavior of quietly swallowing exceptions raised in threads. I believe this is a bug, and threads should always at least log exceptions that bubble all the way out and terminate them.

The implementation should be simple, but I'm not yet familiar enough with the MRI codebase to provide a patch. The exception logging should be logged in the same way top-level exceptions get logged, but perhaps with information about the thread that was terminated because of the exception.

Here is a monkey patch that simulates what I'm hoping to achieve with this bug:


class << Thread
  alias old_new new

  def new(*args, &block)
    old_new(*args) do |*bargs|
      begin
        block.call(*bargs)
      rescue Exception => e
        raise if Thread.abort_on_exception || Thread.current.abort_on_exception
        puts "Thread for block #{block.inspect} terminated with exception: #{e.message}"
        puts e.backtrace.map {|line| "  #{line}"}
      end
    end
  end
end

Thread.new { 1 / 0 }.join
puts "After thread"   

__END__

Output:

system ~/projects/jruby $ ruby thread_error.rb 
Thread for block #<Proc:0x000000010d008a80 / thread_error.rb:17> terminated with exception: divided by 0
  thread_error.rb:17:in `/'
  thread_error.rb:17
  thread_error.rb:7:in `call'
  thread_error.rb:7:in `new'
  thread_error.rb:5:in `initialize'
  thread_error.rb:5:in `old_new'
  thread_error.rb:5:in `new'
  thread_error.rb:17
After thread



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