add support for exception-aware threading

auxilary.py

@@ -1,6 +1,11 @@
-import time, psutil, yaml, os
+'''
+Various helper functions and classes
+'''
+
+import time, yaml, os
 from subprocess import check_output, DEVNULL, CalledProcessError
-from threading import Thread, Event
+from threading import Event
+from exceptionThreading import ExceptionThread
 
 class ConfigFile():
 	'''
@@ -21,21 +26,7 @@ class ConfigFile():
 		with open(self._path, 'w') as f:
 			yaml.dump(self._dict, f, default_flow_style=False)
 
-class async:
-	'''
-	Wraps any function in a thread and starts the thread. Intended to be used as
-	a decorator
-	'''
-	def __init__(self, daemon=False):
-		self._daemon = daemon
-
-	def __call__(self, f):
-		def wrapper(*args, **kwargs):
-			t = Thread(target=f, daemon=self._daemon, args=args, kwargs=kwargs)
-			t.start()
-		return wrapper
-
-class CountdownTimer(Thread):
+class CountdownTimer(ExceptionThread):
 	'''
 	Launches thread which self terminates after some time (given in seconds).
 	Termination triggers some action (a function). Optionally, a sound can be

blinkenLights.py

@@ -1,11 +1,12 @@
 import RPi.GPIO as GPIO
 import time, logging
-from threading import Thread, Event
+from threading import Event
+from exceptionThreading import ExceptionThread
 from itertools import chain
 
 logger = logging.getLogger(__name__)
 
-class Blinkenlights(Thread):
+class Blinkenlights(ExceptionThread):
 	def __init__(self, pin, cyclePeriod=2):
 		self._stopper = Event()
 		self._pin = pin

exceptionThreading.py

@@ -0,0 +1,61 @@
+'''
+Implementation of exception-aware threads, including a listener to be put in
+the top-level thread
+'''
+
+import queue
+from threading import Thread, Event
+
+# Killswitch for exception queue listener. Pass this to top-level thread so it
+# can be called as part of clean up code
+excStopper = Event()
+
+# queue to shuttle exceptions from children to top-level thread
+_excQueue = queue.Queue()
+
+def excChildListener():
+	'''
+	Queue listener to intercept exceptions thrown in child threads that are
+	exception-aware
+	'''
+	while not excStopper.isSet():
+		try:
+			raise _excQueue.get(True)
+			_excQueue.task_done()
+		except queue.Empty:
+			pass
+	while 1:
+		try:
+			raise _excQueue.get(False)
+			_excQueue.task_done()
+		except queue.Empty:
+			break
+
+class ExceptionThread(Thread):
+	'''
+	Thread that passes exceptions to a queue, which is handled by
+	excChildListener in top-level thread
+	'''
+	def __init__(self, group=None, target=None, name=None, args=(), kwargs=None, *, daemon=None):
+		super().__init__(group, target, name, args, kwargs, daemon=daemon)
+		self._queue = _excQueue
+
+	def run(self):
+		try:
+			Thread.run(self)
+		except BaseException as e:
+			self._queue.put(e)
+
+class async:
+	'''
+	Wraps any function in an exception-aware thread and starts the thread.
+	Intended to be used as a decorator
+	'''
+	def __init__(self, daemon=False):
+		self._daemon = daemon
+
+	def __call__(self, f):
+		def wrapper(*args, **kwargs):
+			t = ExceptionThread(target=f, daemon=self._daemon, args=args, kwargs=kwargs)
+			t.start()
+		return wrapper

gmail.py

@@ -1,5 +1,6 @@
 import logging, time
-from auxilary import async, ConfigFile
+from auxilary import ConfigFile
+from exceptionThreading import async
 from smtplib import SMTP
 from datetime import datetime
 from email.mime.multipart import MIMEMultipart

listeners.py

@@ -1,5 +1,5 @@
 import logging, os, sys, stat
-from threading import Thread
+from exceptionThreading import ExceptionThread
 from evdev import InputDevice, ecodes
 from select import select
 from auxilary import waitForPath
@@ -7,7 +7,7 @@ import stateMachine
 
 logger = logging.getLogger(__name__)
 
-class KeypadListener(Thread):
+class KeypadListener(ExceptionThread):
 	def __init__(self, stateMachine, callbackDisarm, callbackArm, soundLib, passwd):
 		
 		ctrlKeys = { 69: 'NUML', 98: '/', 14: 'BS', 96: 'ENTER'}
@@ -115,7 +115,7 @@ class KeypadListener(Thread):
 			
 # TODO: these are not threadsafe
 # TODO: this code gets really confused if the pipe is deleted
-class PipeListener(Thread):
+class PipeListener(ExceptionThread):
 	def __init__(self, callback, path):
 		self._path = path
 		

main.py

@@ -5,6 +5,7 @@ import RPi.GPIO as GPIO
 
 from sharedLogging import unmountGluster # this should be first program module
 from stateMachine import StateMachine
+from exceptionThreading import excChildListener, excStopper
 
 logger = logging.getLogger(__name__)
 
@@ -23,6 +24,7 @@ def clean():
 		logger.critical(traceback.format_exc())
 
 def sigtermHandler(signum, stackFrame):
+	excStopper.set()
 	logger.info('Caught SIGTERM')
 	raise SystemExit
 
@@ -32,15 +34,14 @@ if __name__ == '__main__':
 		
 		GPIO.setwarnings(False)
 		GPIO.setmode(GPIO.BCM)
-
+		
 		stateMachine = StateMachine()
 
 		# TODO: segfaults are annoying :(
 		#~ signal.signal(signal.SIGSEGV, sig_handler)
 		signal.signal(signal.SIGTERM, sigtermHandler)
 
-		while 1:
-			time.sleep(31536000)
+		excChildListener()
 
 	except Exception:
 		logger.critical(traceback.format_exc())

soundLib.py

@@ -1,9 +1,9 @@
-import logging, os, hashlib, queue, threading, time, psutil
+import logging, os, hashlib, queue, time, psutil
+from threading import Event
+from exceptionThreading import ExceptionThread, async
 from pygame import mixer
 from subprocess import call
 from collections import OrderedDict
-from auxilary import async
-from queue import Queue
 
 logger = logging.getLogger(__name__)
 
@@ -89,8 +89,8 @@ class SoundLib:
 		self.volume = 100
 		self._applyVolumesToSounds(self.volume)
 		
-		self._ttsQueue = Queue()
-		self._stop = threading.Event()
+		self._ttsQueue = queue.Queue()
+		self._stop = Event()
 		self._startMonitor()
 
 	def changeVolume(self, volumeDelta):
@@ -187,7 +187,7 @@ class SoundLib:
 		logger.debug('TTS engine received "%s"', text)
 		
 	def _startMonitor(self):
-		self._thread = t = threading.Thread(target=self._ttsMonitor, daemon=True)
+		self._thread = t = ExceptionThread(target=self._ttsMonitor, daemon=True)
 		t.start()
 		logger.debug('Starting TTS Queue Monitor')
 					

stream.py

@@ -16,7 +16,8 @@ import gi, time, os, logging
 from datetime import datetime
 from threading import Thread, Lock
 
-from auxilary import async, waitForPath, mkdirSafe
+from auxilary import waitForPath, mkdirSafe
+from exceptionThreading import async
 from sharedLogging import gluster
 
 logger = logging.getLogger(__name__)

webInterface.py

@@ -5,7 +5,7 @@ from flask_wtf import FlaskForm
 from wtforms.fields import StringField, SubmitField
 from wtforms.validators import InputRequired
 
-from auxilary import async
+from exceptionThreading import async
 
 logger = logging.getLogger(__name__)