A python deamon that spins of an extra thread and acts on signals

deamontest.py

# Concept of daemon that spins of an extra thread and can be controlled by signals
#
# I have rewritten the script slightly after I did this log. So some output has changed a bit,
# the signals are still the same
#
# This has to be run with python3
#
# Developed and tested on debian 9.9 - all modules installed with apt
#
# morten@latlon:/home/disk0/m/GardenController$ sudo tail -f /var/log/messages &
# morten@latlon:/home/disk0/m/GardenController$ python3 controller_daemon.py && ps -u morten | grep py
# 26808 ?        00:00:00 python3
# morten@latlon:/home/disk0/m/GardenController$ Jun  2 20:42:15 latlon controller_daemon.py: starting up
# Jun  2 20:42:15 latlon controller_daemon.py: Thread started
# Jun  2 20:42:15 latlon controller_daemon.py: Thread still active
# Jun  2 20:42:30 latlon controller_daemon.py: Thread still active
# morten@latlon:/home/disk0/m/GardenController$ kill -SIGUSR1 26808
# Jun  2 20:42:40 latlon controller_daemon.py: sending message to thread
# Jun  2 20:42:45 latlon controller_daemon.py: Thread got it
# Jun  2 20:42:45 latlon controller_daemon.py: Thread still active
# morten@latlon:/home/disk0/m/GardenController$ kill -SIGUSR2 `cat /tmp/controller.pid`
# Jun  2 20:42:51 latlon controller_daemon.py: Got it!
# morten@latlon:/home/disk0/m/GardenController$ kill -SIGUSR1 26808
# Jun  2 20:42:55 latlon controller_daemon.py: sending message to thread
# Jun  2 20:43:00 latlon controller_daemon.py: Thread got it
# Jun  2 20:43:00 latlon controller_daemon.py: Thread still active
# morten@latlon:/home/disk0/m/GardenController$ kill -SIGTERM 26808
# Jun  2 20:43:20 latlon controller_daemon.py: Starting to exit
# Jun  2 20:43:20 latlon controller_daemon.py: starting to end process
# Jun  2 20:43:20 latlon controller_daemon.py: ending process
# Jun  2 20:43:30 latlon controller_daemon.py: Ending thread
# Jun  2 20:43:30 latlon controller_daemon.py: Finished

# After a signal is sent, it may take up to 5 secs before it is processed by the main deamon thread and up to 15 secs 
# afterwards for the subthread. - Nothing happens during the time.sleep()s. To get the code more responsive, it is
# possible to have short sleeps and use some other checks to see if the time is due to do whatever is to be done, but this is
# meant to be an as simple as possible example.
#

import daemon
import daemon.pidfile
import time
import signal
import threading
import os
import syslog

EXITDAEMON=False
MSGTHREAD=False


def runthread(evtexit,evtmsg):
  syslog.syslog(syslog.LOG_NOTICE,"Thread started")
  while True:
    if evtexit.isSet():
      syslog.syslog(syslog.LOG_NOTICE,"Ending thread")
      return()
    if evtmsg.isSet():
      syslog.syslog(syslog.LOG_NOTICE,"Thread got it")
    syslog.syslog(syslog.LOG_NOTICE,"Thread still active")
    time.sleep(15)

def do_work():
  global MSGTHREAD
  global EXITDAEMON
  syslog.syslog(syslog.LOG_NOTICE,"starting up")
  stopthread=threading.Event()
  msgthread=threading.Event()
  trd=threading.Thread(target=runthread,args = (stopthread,msgthread, ))
  trd.start()
  while True:
    with open("/tmp/current_time.txt", "w") as f:
      f.write("The time is now " + time.ctime())
    if MSGTHREAD:
      msgthread.set()
      syslog.syslog(syslog.LOG_NOTICE,"sending message to thread")
      MSGTHREAD=False
    if EXITDAEMON:
      syslog.syslog(syslog.LOG_NOTICE,"starting to end process ")
      break
    time.sleep(5)        

  # Will get here after a break caused by EXITDEAMON being true    
  syslog.syslog(syslog.LOG_NOTICE,"ending process")
  stopthread.set() # tells the thread to finish its business
  trd.join()       # ends thread
  syslog.syslog(syslog.LOG_NOTICE,"Finished")
    
def receiveSignal(signalNumber, frame):  
  syslog.syslog("Got it!")

def shutdown(signum,frame):
  global EXITDAEMON
  EXITDAEMON=True
  syslog.syslog(syslog.LOG_NOTICE,"Ready to exit")
    
    
def msgthread(signum,frame):
  global MSGTHREAD
  MSGTHREAD=True
  syslog.syslog(syslog.LOG_NOTICE,"Will send message to thread") # This was added after I did the log at the top
    
def run():
    with daemon.DaemonContext(signal_map={
            signal.SIGTERM: shutdown,
            signal.SIGUSR2: receiveSignal,
            signal.SIGUSR1: msgthread
        },pidfile=daemon.pidfile.PIDLockFile('/tmp/controller.pid')):
      # If making a daemon that is to be run as root, put the pidfile in /var/run, or maybe the users home dir
        do_work()

if __name__ == "__main__":
    run()