Debug a memory leak, or a hanging process on a rails application.

ruby process debug.md

Attach the process to a gdb session.

sudo gdb $(rbenv which ruby) $(pgrep thin)

Enter this on the gdb prompt.

set $ary = (int)backtrace(-1)
set $count = *($ary+8)
set $index = 0
while $index < $count
  x/1s *((int)rb_ary_entry($ary, $index)+12)
  set $index = $index + 1
end

You will see the output at the console running the thin command.

Taken from http://weblog.jamisbuck.org/2006/9/22/inspecting-a-live-ruby-process.html