[ruby-core:57617] [ruby-trunk - Feature #6647] Exceptions raised in threads should be logged

Issue #6647 has been updated by headius (Charles Nutter).


ko1 (Koichi Sasada) wrote:
> Sorry, it is not same, but we can consier that.
> 
> BTW, I think it true as default is good idea.

So to summarize:

* Exceptions will log when they bubble out of a thread, as with -d, unless Thread#report_on_exception == false
* Thread#report_on_exception defaults to true

Can we do this for 2.1?

> IMO, inter-thread communication via exception with Thread#join should be bad idea.

+1

I had originally wanted something similar to Java, where you can set an "unhandled exception handler" for any thread. That would cover all cases, and the default case would be to just report the error. I was unsuccessful in specifying it because I wasn't sure how it should interact with abort_on_exception=.
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Feature #6647: Exceptions raised in threads should be logged
https://bugs.ruby-lang.org/issues/6647#change-42230

Author: headius (Charles Nutter)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: current: 2.1.0


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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