debugging daemonized processes

[bukzor]

I'm not-rarely placed in a situation where I need to debug a python process that has its stdio files closed or otherwise connected elsewhere.

I currently "solve" this through some awful hackery wherein I open /dev/ptsXX and shove it into place of the disconnected file descriptors. This requires that I open an unused terminal beforehand and sleep 99999 in it, to avoid both pudb and bash reading my input at the same time.

Surely there's a better way. Do any of you have a clue what it might be?

[bukzor]

Here is my awful hack, purely for historical purposes. One of the (several) major problems with it is that it errors out (I forget the exact error) if it's hit twice in a particular process.

import sys
import os
TTY = '/dev/pts/7'

os.close(0)
mytty = open(TTY)
sys.stdin = sys.__stdin__ = mytty
os.dup2(mytty.fileno(), 0)

os.close(1)
mytty = open(TTY, 'w')
sys.stdout = sys.__stdout__ = mytty
os.dup2(mytty.fileno(), 1)

os.close(2)
mytty = open(TTY, 'w')
sys.stderr = sys.__stderr__ = mytty
os.dup2(mytty.fileno(), 2)


import pudb; pudb.set_trace()

[inducer]

Short of full client-server pudb (which I don't think is a viable option architecturally, at least in the short term), a way to make your hacky version a bit cleaner would be to have the process expose an SSH server, which seems like it's doable with reasonable effort. Two issue with that are

• whose main loop is it anyway?
• how to keep the debugger from wanting to debug the SSH infrastructure

I don't have the spare cycles to implement it, but I'd be happy to have a discussion and merge a patch.