pymenderqemu.py

#!/usr/bin/env python2

from __future__ import print_function
import subprocess
import os
import signal
import time


MENDER_QEMU_PATH = os.path.join(os.path.dirname(__file__), "mender-qemu")

def set_new_pg():
    try:
        print('new process', os.getpid(),'group', os.getpgrp(), 'session', os.getsid(0))
        os.setsid()
        print('current group', os.getpgrp(), 'session', os.getsid(0))
    except Exception as exc:
        print(exc)


class ProcessGroupPopen(subprocess.Popen):
    """Wrapper for subprocess.Popen that starts the underlying process in a
    separate process group"""

    def __init__(self, *args, **kwargs):
        # for Python > 3.2 it's enough to set start_new_session=True
        super(ProcessGroupPopen, self).__init__(*args,
                                                preexec_fn=set_new_pg,
                                                **kwargs)

    def __signal(self, sig):
        os.killpg(self.pid, sig)

    def terminate(self):
        self.__signal(signal.SIGTERM)

    def kill(self):
        self.__signal(signal.SIGKILL)


def start_qemu(qenv=None):
    """Start qemu and return a subprocess.Popen object corresponding to a running
    qemu process. `qenv` is a dict of environment variables that will be added
    to `subprocess.Popen(..,env=)`.

    Once qemu is stated, a connection over ssh will attempted, so the returned
    process is actually a qemu instance with fully booted guest os.

    The helper uses `meta-mender-qemu/scripts/mender-qemu` to start qemu, thus
    you can use `VEXPRESS_IMG`, `QEMU_DRIVE` and other environment variables to
    override the default behavior.
    """
    env = dict(os.environ)
    if qenv:
        env.update(qenv)

    print('starting process')
    # proc = subprocess.Popen([MENDER_QEMU_PATH, "-snapshot"],
    #                         preexec_fn=set_new_pg,
    #                         env=env)
    proc = ProcessGroupPopen([MENDER_QEMU_PATH, "-snapshot"],
                             env=env)
    print('started, wait 30s before terminating')
    time.sleep(30)
    print('terminating')
    proc.terminate()
    proc.wait()


if __name__ == '__main__':
    start_qemu()