Update shift change notification to consider microsecond timestamps (#5196)

Related to https://github.com/grafana/support-escalations/issues/12893

engine/apps/alerts/tasks/notify_ical_schedule_shift.py

@@ -90,11 +90,17 @@ def notify_ical_schedule_shift(schedule_pk):
         prev_shifts = convert_prev_shifts_to_new_format(prev_shifts, schedule)
         prev_shifts_updated = True
 
-    # convert datetimes which was dumped to str back to datetime to calculate shift diff correct
-    str_format = "%Y-%m-%d %X%z"
+    def _parse_timestamp(timestamp: str) -> datetime.datetime:
+        # convert datetimes which was dumped to str back to datetime to calculate shift diff correct
+        try:
+            dt = datetime.datetime.strptime(timestamp, "%Y-%m-%d %X%z")
+        except ValueError:
+            dt = datetime.datetime.strptime(timestamp, "%Y-%m-%d %X.%f%z")
+        return dt
+
     for prev_shift in prev_shifts:
-        prev_shift["start"] = datetime.datetime.strptime(prev_shift["start"], str_format)
-        prev_shift["end"] = datetime.datetime.strptime(prev_shift["end"], str_format)
+        prev_shift["start"] = _parse_timestamp(prev_shift["start"])
+        prev_shift["end"] = _parse_timestamp(prev_shift["end"])
 
     # get shifts in progress now
     now = datetime.datetime.now(datetime.timezone.utc)

engine/apps/alerts/tests/test_notify_ical_schedule_shift.py

@@ -498,6 +498,45 @@ def test_next_shift_changes_no_triggering_notification(
     assert not mock_slack_api_call.called
 
 
+@pytest.mark.django_db
+def test_current_shifts_using_microseconds(
+    make_organization_and_user_with_slack_identities,
+    make_user,
+    make_schedule,
+):
+    organization, _, _, _ = make_organization_and_user_with_slack_identities()
+    user1 = make_user(organization=organization, username="user1")
+    schedule = make_schedule(
+        organization,
+        schedule_class=OnCallScheduleCalendar,
+        name="test_schedule",
+        channel="channel",
+        prev_ical_file_overrides=None,
+        cached_ical_file_overrides=None,
+    )
+    schedule.refresh_ical_file()
+    schedule.current_shifts = json.dumps(
+        {
+            "test_shift_uid": {
+                "users": [user1.pk],
+                "start": timezone.now().replace(microsecond=123456),
+                "end": timezone.now().replace(microsecond=654321) + timezone.timedelta(days=1),
+                "all_day": False,
+                "priority": 1,
+                "priority_increased_by": 0,
+            }
+        },
+        default=str,
+    )
+    schedule.empty_oncall = False
+    schedule.save()
+
+    with patch("apps.slack.client.SlackClient.chat_postMessage") as mock_slack_api_call:
+        notify_ical_schedule_shift(schedule.pk)
+
+    assert mock_slack_api_call.called
+
+
 @pytest.mark.django_db
 def test_lower_priority_changes_no_triggering_notification(
     make_organization_and_user_with_slack_identities,