receive task: log delay from when Object was created

for #1308

protocol.py

@@ -829,7 +829,10 @@ def receive(from_cls, obj, authed_as=None, internal=False):
 
         pruned = {k: v for k, v in obj.as1.items()
                   if k not in ('contentMap', 'replies', 'signature')}
-        logger.info(f'Receiving {from_cls.LABEL} {obj.type} {id} AS1: {json_dumps(pruned, indent=2)}')
+        delay = ''
+        if request.headers.get('X-AppEngine-TaskRetryCount') == '0' and obj.created:
+            delay = f'({(util.now().replace(tzinfo=None) - obj.created).total_seconds()} s behind)'
+        logger.info(f'Receiving {from_cls.LABEL} {obj.type} {id} {delay} AS1: {json_dumps(pruned, indent=2)}')
 
         # does this protocol support this activity/object type?
         from_cls.check_supported(obj)

tests/test_protocol.py

@@ -2958,7 +2958,7 @@ def test_receive_task_handler(self):
         resp = self.post('/queue/receive', data={
             'obj': obj.key.urlsafe(),
             'authed_as': 'fake:other',
-        })
+        }, headers={'X-AppEngine-TaskRetryCount': '0'})
         self.assertEqual(204, resp.status_code)
         obj = Object.get_by_id('fake:post#bridgy-fed-create')
         self.assertEqual('ignored', obj.status)