Debugging stuck Ruby processes

stuck.rb

# Use this to get the stacktrace of any ruby process by calling kill -USR1 <pid>
# For rspec, put this in the spec_helper.rb, for rails in some initializer.
puts "ruby process pid: #{Process.pid}"

trap 'USR1' do
  threads = Thread.list

  puts
  puts "=" * 80
  puts "Received USR1 signal; printing all #{threads.count} thread backtraces."

  threads.each do |thr|
    description = thr == Thread.main ? "Main thread" : thr.inspect
    puts
    puts "#{description} backtrace: "
    puts thr.backtrace.join("\n")
  end

  puts "=" * 80
end