Better bad state recovery from long executions

asyncron/workers.py

@@ -127,9 +127,23 @@ class AsyncronWorker:
 			status_reason = "Worker died during execution",
 			status = "A", worker_lock = None
 		)
-		#DONT print anything in here!
+
 		#if count: print(f"Had to cancel {count} task(s).") #cls.log.warning
-		self.model.delete()
+
+		# Almost always, a worker can delete it's model from the db,
+		# But it seems that there is a sitation where despite Task.worker_lock being delete=SET_NULL,
+		# That still a race condition can cause an IntegrityError, If I'm correct about the root cause,
+		# just attempting to self delete with a small interval, Should Fix the issue.
+		# Error example:
+		# - django.db.utils.IntegrityError: update or delete on table "asyncron_worker" violates foreign key constraint "asyncron_task_worker_lock_id_0bb55026_fk_asyncron_worker_id" on table "asyncron_task"
+
+		for attempt in range(3):
+			try:
+				self.model.delete()
+			except IntegrityError:
+				time.sleep( 0.1 )
+			else: break
+
 		#self.loop.call_soon(self.started.set)
 
 	def attach_django_signals( self ):
@@ -194,9 +208,8 @@ class AsyncronWorker:
 						loop_wait = 0
 
 					else:
-						await Worker.objects.filter(
-							is_master = True,
-							last_crowning_attempt__lte = timezone.now() - timezone.timedelta( minutes = 5 )
+						await Worker.objects.filter( is_master = True ).filter(
+							models.Q(last_crowning_attempt = None) | models.Q(last_crowning_attempt__lte = timezone.now() - timezone.timedelta( minutes = 5 ))
 						).aupdate( is_master = False )