the-screenless-office/screenless/mgmt.py

"""
The Management - this module takes care of loading and running subordinate
  bureaus in the office organization.  Bureaus are enabled in the file
  "~/.screenless/mgmt.ini":
  [mgmt]
  bureaus = ihr typing myburo and so on
"""
import configparser
import importlib
import multiprocessing
import os
import signal
import time


class Management:
    """
    Management is the executive of the Screenless Office.  It can start, stop
    and reconfigure the subordinate bureaus of the office.
    """
    def __init__(self):
        basepath = os.path.expanduser("~/.screenless")
        if not os.path.exists(basepath):
            os.mkdir(basepath)
        os.chdir(basepath)

        self.procs = {}
        self.org_chart = []
        self._load_config()

    def _load_config(self): 
        config = configparser.ConfigParser()
        try:
            config.read("mgmt.ini")
            self.org_chart = config["mgmt"]["bureaus"].split()
        except KeyError:
            config["mgmt"] = {"bureaus":
                              "ihr typing publicrelations photography jokes"}
            with open("mgmt.ini", "w") as configfile:
                config.write(configfile)
            print("Created new mgmt.ini config file.  Please modify to suit.")
            self.org_chart = config["mgmt"]["bureaus"].split()

    def _start_bureaus(self):
        """
        Initialized and start all child bureaus
        """
        for buro in self.org_chart:
            # TODO: this may need some sanity checking for crash/reload
            lib = importlib.import_module("bureau." + buro)
            proc = multiprocessing.Process(target=lib.main)
            self.procs[buro] = proc
            proc.start()

    def _stop_bureaus(self):
        """
        Terminates all running bureau children
        """
        for buro in self.org_chart:
            proc = self.procs[buro]
            proc.terminate()

    def reload(self, signum=None, frame=None):
        """
        stop all bureaus, reload config, restart all bureaus.
        Note, this may cause a loss of state in some cases.
        """
        self._stop_bureaus()
        self._load_config()
        self._start_bureaus()

    def run(self):
        """
        main loop for Management, will restart crashed bureaus
        and reload everything when sent a SIGHUP
        """
        with open("mgmt.pid", "w") as pfile:
            pfile.write(str(os.getpid()))

        signal.signal(signal.SIGHUP, self.reload)

        self._start_bureaus()
        while True:
            for buro in self.org_chart:
                proc = self.procs[buro]
                if not proc.is_alive():
                    print("bureau", buro, "has crashed!  Call the consultants!")
                    print("restarting...")
                    #TODO this should probably only retry a few times
                    proc.start()
            time.sleep(1)


if __name__ == "__main__":
    mgmt = Management()
    mgmt.run()