Update aprsd thread base class to use queue

This patch updates the main aprsd threads class to use
a shared queue to notify all aprsd thread classes they need
to exit.  This ensures any closing down of sockets, etc happens from
inside the context of the thread itself, not the MainThread that
calls stop.

aprsd/threads/aprsd.py

@@ -1,7 +1,10 @@
 import abc
 import logging
+from queue import Queue
 import threading
 
+import wrapt
+
 
 LOG = logging.getLogger("APRSD")
 
@@ -12,41 +15,64 @@ class APRSDThreadList:
     _instance = None
 
     threads_list = []
-    lock = None
+    lock = threading.Lock()
+    global_queue = Queue()
 
     def __new__(cls, *args, **kwargs):
         if cls._instance is None:
             cls._instance = super().__new__(cls)
-            cls.lock = threading.Lock()
             cls.threads_list = []
         return cls._instance
 
+    @wrapt.synchronized(lock)
     def add(self, thread_obj):
-        with self.lock:
+        thread_obj.set_global_queue(self.global_queue)
         self.threads_list.append(thread_obj)
 
+    @wrapt.synchronized(lock)
     def remove(self, thread_obj):
-        with self.lock:
         self.threads_list.remove(thread_obj)
 
+    @wrapt.synchronized(lock)
     def stop_all(self):
+        self.global_queue.put_nowait({"quit": True})
         """Iterate over all threads and call stop on them."""
-        with self.lock:
         for th in self.threads_list:
-                LOG.debug(f"Stopping Thread {th.name}")
+            LOG.info(f"Stopping Thread {th.name}")
             th.stop()
 
+    @wrapt.synchronized(lock)
     def __len__(self):
-        with self.lock:
         return len(self.threads_list)
 
 
 class APRSDThread(threading.Thread, metaclass=abc.ABCMeta):
+
+    global_queue = None
+
     def __init__(self, name):
         super().__init__(name=name)
         self.thread_stop = False
         APRSDThreadList().add(self)
 
+    def set_global_queue(self, global_queue):
+        self.global_queue = global_queue
+
+    def _should_quit(self):
+        """ see if we have a quit message from the global queue."""
+        if self.thread_stop:
+            return True
+        if self.global_queue.empty():
+            return False
+        msg = self.global_queue.get(timeout=1)
+        if not msg:
+            return False
+        if "quit" in msg and msg["quit"] is True:
+            # put the message back on the queue for others
+            self.global_queue.put_nowait(msg)
+            self.thread_stop = True
+            return True
+
     def stop(self):
         self.thread_stop = True
 
@@ -54,11 +80,15 @@ class APRSDThread(threading.Thread, metaclass=abc.ABCMeta):
     def loop(self):
         pass
 
+    def _cleanup(self):
+        """Add code to subclass to do any cleanup"""
+
     def run(self):
         LOG.debug("Starting")
-        while not self.thread_stop:
+        while not self._should_quit():
             can_loop = self.loop()
             if not can_loop:
                 self.stop()
+        self._cleanup()
         APRSDThreadList().remove(self)
         LOG.debug("Exiting")