I’ve been looking at python for various build automation. I had what I thought would be a simple problem:<\/p>\n
The python subprocess<\/a> module gets about 80% there. You can launch a process, and hook up stdout\/stderr\/stdin. You can poll the process for completion. But subprocess doesn’t have a simple parameter for process timeout. Total time spent: 45 minutes.<\/p>\n So, you use a loop or a thread to wait for the process and kill it if it takes too long, right? Subprocess doesn’t have an instance method to kill the process. Answer according to #python on freenode? os.kill(theprocess.pid, signal.SIGTERM)<\/tt>. Except that this apparently doesn’t work on Windows: you have to emulate it<\/a>. Total time spent: 1.5 hours.<\/p>\n This works, on unixy systems. But it fails miserably on Windows. It turns out that on Windows when you kill a process, any subprocesses that were launched don’t get killed. So I went searching code that I thought must have already solved this problem: BuildBot<\/a> launches processes and has to kill them, right? Well, it turns out that BuildBot uses Twisted<\/a> to do the dirty work. Twisted completely ignores the problem, as far as I can tell. It doesn’t use subprocess, but instead has a file called _dumbwin32proc.py<\/tt> which provides the event-driven access to the process pipes and status. This file is uglier than the devil’s rear end. Total time spent: 2.5 hours.<\/p>\n