detach.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from __future__ import unicode_literals, absolute_import, print_function
import gevent
import subprocess
from functools import partial
from six import int2byte, StringIO
import os
import logging


CMD = "/proc/{}/cmdline"
ENV = "/proc/{}/environ"
STDERR = "/proc/{}/fd/2"

ZERO = int2byte(0x00)
COLOR = {"AV_LOG_FORCE_COLOR": "TRUE"}

cmd = ["ffmpeg", "-y", "-i",
    "/home/ponimas/tmp/test.mp4",
    "-c:v", "h264", "-c:a", "copy", 
    "-f", "mp4", "/dev/null"]


def start_process(cmd, env=None):
    if env is None:
        env = {}
    return subprocess.Popen(
        cmd, 
        close_fds=True,
        preexec_fn=os.setsid,
        env=env,
        stderr=subprocess.PIPE).pid


def monitor(pid):
    with open(CMD.format(pid)) as cmd:
        cmd_line = cmd.readline().split(ZERO)[:-1]

    with open(ENV.format(pid)) as env:
        env = dict(x.split("=") for x in
                   env.readline().split(ZERO) if x)

    fd = os.open(STDERR.format(pid), os.O_NONBLOCK|os.O_RDONLY)
    
    buff = StringIO()
    for data in iter(partial(gevent.os.nb_read, fd, 2048), ""):
        buff.write(data)
        if data.endswith(("\r", "\n")):
            print("from pid {} - {}".format(pid, buff.getvalue().strip()))
            buff = StringIO()
        gevent.sleep()

    print("Process {} failed - restarting".format(pid))

    pid = start_process(cmd_line, env)
    gevent.spawn(monitor, pid)


if __name__ == "__main__":
    import argparse
    import gevent.backdoor
    parser = argparse.ArgumentParser()
    parser.add_argument("-p", type=int, nargs="+")
    cmdargs = parser.parse_args()
    if not cmdargs.p:
        pid = start_process(cmd)
        gevent.spawn(monitor, pid)
    else:
        for pid in cmdargs.p:
            gevent.spawn(monitor, pid)

    gevent.backdoor.BackdoorServer(("127.0.0.1", 12432), locals=locals(), banner="Hallo!!").serve_forever()
    # while True:
    #     gevent.sleep(100)