How can one identify children of a child process?

I have a long-running Python program that starts and stops a Postgres server as part of its operation. I stop the server by using subprocess to spawn pg_ctl -m fast. As a fall-back, I check the return code and, if it failed, I then run pg_ctl -m immediate.

The problem is that sometimes both fail. I haven't been able to reproduce this myself, but it happens with some frequency for users of my program. I log stdout/stderr from the pg_ctl calls, but don't get any useful info there. As far as I can tell, ei开发者_如何学运维ther the master process or its children have stopped responding to SIGQUIT, and the only way to terminate them is with SIGKILL, which pg_ctl does not use.

I've basically exhausted ideas on the Postgres side. I'm using Postgres 8.3, so I'm sure upgrading to a more recent version would resolve this, but unfortunately that is not an option for me. The only solution I can come up with is to kill the children manually. But I don't know how to distinguish between the children spawned by my pg_ctl start and other postgres processes that might be running on the machine.

Is there a way to identify a process as a child of another process that I spawned? A cross-platform method of doing this from Python would be ideal, but I'm willing to write a C extension if there exist APIs on Windows/Linux/UNIX to do this.

Here is a simple shell script solution:

pgrep -P $(head -1 $PGDATA/postmaster.pid)

This prints out the PIDs of the child processes.

I'm not aware of a standard Python module that can get that information. pgrep gets the information from /proc, so you could reimplement that in Python, but I doubt that it would be worth it.

The C++ standard does not know of multiprocess systems. There is, therefore, no API for interacting with processes. (After all, how would the standard mandate a multiprocess system on an 8 bit microcontroller?)

Moreover, some platforms (e.g. the Win32 Subsystem on Windows NT) do not keep track of process parent child relationships. (NT does under the hood but you'd have to call undocumented APIs to get at the information)

I'm fairly certain POSIX does define APIs like this, but I have not used them myself.