bonus:

added a '(late)' timestamp in the monitor when a timestamp arrives > 60 seconds late.

atdb/taskdatabase/services/algorithms.py

@@ -266,7 +266,8 @@ def convert_monitor_to_html(request, monitor_data):
             d1 = datetime.utcnow().replace(tzinfo=None)
             d2 = record.timestamp.replace(tzinfo=None)
             delta = d1 - d2
-            if delta.seconds > 60:
+            # if the heartbeat is 30 minutes late, show '(late)' in red
+            if delta.seconds > 1800:
                 line += '<td class="error">' + str(record.timestamp.strftime(TIME_FORMAT)) + " - (late)</td>"
             else:
                 line += '<td>' + str(record.timestamp) + "</td>"