python-debug

• study

  set breakpoint on line number by gdb ?
  http://www.macs.hw.ac.uk/~hwloidl/hackspace/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/share/doc/gcc-linaro-arm-linux-gnueabihf-raspbian/html/gdb/Basic-Python.html
  https://wiki.python.org/moin/DebuggingWithGdb
  

• 注意

  1. debuginfo-install commnad --> yum install yum-utils
  

• 參考資料

  https://pymotw.com/2/sys/tracing.html
  https://stripe.com/blog/exploring-python-using-gdb
  

• trace flow by sys.settrace() 以openstack swift 的 set metadata 為例

1. add global function trace_calls(), 如下

def trace_calls(frame, event, arg):
  if event != 'call':
    return
  co = frame.f_code
  func_name = co.co_name
  if func_name == 'write':
    # Ignore write() calls from print statements
    return
  func_line_no = frame.f_lineno
  func_filename = co.co_filename
  caller = frame.f_back
  caller_line_no = caller.f_lineno
  caller_filename = caller.f_code.co_filename
  print 'Call to %s on line %s of %s' % \
    (func_name, func_line_no, func_filename)
  return

2. 將 sys.settrace() 加到 POST function, 因set metadata 會走進 container 的 post function, 如下

def POST(self, req):
    """Handle HTTP POST request."""
    sys.settrace(trace_calls)
    ...

3. post function 的 children functions 會顯示在 /var/log/messages