Use _stop_event consistently across all threads as the way to signal that it should stop. Add thread joins with timeouts to allow the program to exit cleanly

providers/sigrefdata/sig_ref_data_provider.py

@@ -1,5 +1,6 @@
 import logging
 from datetime import datetime
+from threading import Event
 
 import pytz
 
@@ -19,7 +20,7 @@ class SIGRefDataProvider:
         self.last_update_time = datetime.min.replace(tzinfo=pytz.UTC)
         self.status = "Not Started" if self.enabled else "Disabled"
         self.reference_count = 0
-        self._stop = False
+        self._stop_event = Event()
 
     def start(self):
         """Start the provider. This should return immediately after spawning threads to access the remote resources"""
@@ -30,7 +31,7 @@ class SIGRefDataProvider:
         """Stop any threads and prepare for application shutdown. Subclasses should implement this method and call
         super()."""
 
-        self._stop = True
+        self._stop_event.set()
 
     def _add_data(self, new_data):
         """Add all the provided reference data objects to the data store."""
@@ -43,7 +44,7 @@ class SIGRefDataProvider:
                 # For the big data sources, loading will take a few minutes. If we want to shut down the software neatly
                 # within the first few minutes of startup, we need a way to abort this expensive process of filling up the
                 # disk cache.
-                if self._stop:
+                if self._stop_event.is_set():
                     break
 
         self.reference_count = len(new_data)