Attempt to fix CPU utilisation bug by preventing the heartbeat callback leak in the SSE stream handlers and replacing Timer-based with Event-based threads. Also compiled regexes in advance for DXCC callsign lookups for efficiency, and fixed my misunderstanding of what Queue.empty() does

server/webserver.py

@@ -5,6 +5,7 @@ import os
 import tornado
 from tornado.web import StaticFileHandler
 
+from core.utils import empty_queue
 from server.handlers.api.addspot import APISpotHandler
 from server.handlers.api.alerts import APIAlertsHandler, APIAlertsStreamHandler
 from server.handlers.api.lookups import APILookupCallHandler, APILookupSIGRefHandler, APILookupGridHandler
@@ -105,7 +106,7 @@ class WebServer:
                 if q.full():
                     logging.warn("A full SSE spot queue was found, presumably because the client disconnected strangely. It has been removed.")
                     self.sse_spot_queues.remove(q)
-                    q.empty()
+                    empty_queue(q)
             except:
                 # Probably got deleted already on another thread
                 pass
@@ -114,7 +115,7 @@ class WebServer:
                 if q.full():
                     logging.warn("A full SSE alert queue was found, presumably because the client disconnected strangely. It has been removed.")
                     self.sse_alert_queues.remove(q)
-                    q.empty()
+                    empty_queue(q)
             except:
                 # Probably got deleted already on another thread
                 pass