django: add logic to summarize events from same pkt

Signed-off-by: Jonas Remmert <jremmert@gmx.net>

server/django/sensordata/serializers/base.py

@@ -15,6 +15,8 @@
 )
 from ..tasks import process_pending_operations
 import logging
+from django.utils import timezone
+from datetime import timedelta
 
 logger = logging.getLogger(__name__)
 
@@ -47,17 +49,36 @@ def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.event = None
 
+    def get_existing_event(self, ep, event_type):
+        """
+        Check for an existing event for the given endpoint and event type
+        created within the last 5 seconds.
+        """
+        five_seconds_ago = timezone.now() - timedelta(seconds=5)
+        return Event.objects.filter(
+            endpoint=ep,
+            event_type=event_type,
+            created_at__gte=five_seconds_ago
+        ).first()
+
 
     def create_event(self, ep, event_type):
         """
-        Create an Event instance for the given endpoint and event type. If no event
-        is created, the resource data won't be associated with any event.
+        Create an Event instance for the given endpoint and event type. If no
+        event is created, the resource data won't be associated with any event.
+        If a recent event exists already, we assume that the new data is just
+        an additional package and belongs to the same event.
         """
-        event_data = {
-            'endpoint': ep,
-            'event_type': event_type,
-        }
-        self.event = Event.objects.create(**event_data)
+        existing_event = self.get_existing_event(ep, event_type)
+
+        if existing_event:
+            self.event = existing_event
+        else:
+            event_data = {
+                'endpoint': ep,
+                'event_type': event_type,
+            }
+            self.event = Event.objects.create(**event_data)
 
 
     def handle_resource(self, ep, obj_id, res, ts=None):