add msg send retry after delay

shiftregister/app/tasks.py

@@ -41,11 +41,20 @@ def send_messages():
 # those messages will be picked up by the cron send later
 # once we have decided to continue sending messages
 @shared_task
-def send_message(msgid):
+def send_message(msgid, is_retry=False):
     if not global_preferences["helper__send_sms"]:
         return
     with transaction.atomic():
-        msg = Message.objects.select_for_update().get(pk=msgid)
+        msgs = Message.objects.select_for_update().filter(pk=msgid)[:1]
+        if not msgs:
+            if not is_retry:
+                print("message not found, retrying")
+                send_message.apply_async((msgid, True), countdown=0.2)
+                return
+            else:
+                print(f"message {msgid} not found in retry, giving up")
+                return
+        msg = msgs[0]
         if msg.sent_at:
             return
         send(msg)