Show 100 latest alerts on alert group page (#1417)

# What this PR does
Make internal API return 100 latest alerts for alert group.

## Which issue(s) this PR fixes
https://github.com/grafana/oncall/issues/857

## Checklist

- [x] Tests updated
- [x] `CHANGELOG.md` updated

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Moved reCAPTCHA to backend environment variable for more flexible configuration between different environments.
 - Add pagination to schedule listing
+- Show 100 latest alerts on alert group page ([1417](https://github.com/grafana/oncall/pull/1417))
 
 ## v1.1.29 (2023-02-23)
 

engine/apps/api/serializers/alert_group.py

@@ -204,12 +204,7 @@ class AlertGroupSerializer(AlertGroupListSerializer):
         Overriding default alerts because there are alert_groups with thousands of them.
         It's just too slow, we need to cut here.
         """
-        alerts = obj.alerts.all()[:100]
-
-        if len(alerts) > 90:
-            for alert in alerts:
-                alert.title = str(alert.title) + " Only last 100 alerts are shown. Use OnCall API to fetch all of them."
-
+        alerts = obj.alerts.order_by("-pk")[:100]
         return AlertSerializer(alerts, many=True).data
 
     def get_paged_users(self, obj):

engine/apps/api/tests/test_alert_group.py

@@ -1548,6 +1548,43 @@ def test_alert_group_preview_body_invalid_template_syntax(
     assert response.data["preview"] == "Template Error: No test named 'None' found."
 
 
+@pytest.mark.django_db
+def test_grouped_alerts(
+    make_organization_and_user_with_plugin_token,
+    make_alert_receive_channel,
+    make_alert_group,
+    make_alert,
+    make_user_auth_headers,
+):
+    organization, user, token = make_organization_and_user_with_plugin_token()
+    alert_receive_channel = make_alert_receive_channel(organization)
+    alert_group = make_alert_group(alert_receive_channel)
+
+    # create 101 alerts and check that only 100 are returned
+    for i in range(101):
+        make_alert(
+            alert_group=alert_group,
+            created_at=timezone.datetime.min + timezone.timedelta(minutes=i),
+            raw_request_data=alert_receive_channel.config.example_payload,
+        )
+
+    client = APIClient()
+    url = reverse("api-internal:alertgroup-detail", kwargs={"pk": alert_group.public_primary_key})
+
+    response = client.get(url, **make_user_auth_headers(user, token))
+
+    assert response.status_code == status.HTTP_200_OK
+    assert len(response.json()["alerts"]) == 100
+
+    first_alert_created_at = response.json()["alerts"][0]["created_at"]
+    last_alert_created_at = response.json()["alerts"][-1]["created_at"]
+
+    first_alert_created_at = timezone.datetime.strptime(first_alert_created_at, "%Y-%m-%dT%H:%M:%S.%fZ")
+    last_alert_created_at = timezone.datetime.strptime(last_alert_created_at, "%Y-%m-%dT%H:%M:%S.%fZ")
+
+    assert first_alert_created_at > last_alert_created_at
+
+
 @pytest.mark.django_db
 def test_alert_group_paged_users(
     make_user_for_organization,

grafana-plugin/src/pages/incident/Incident.tsx

@@ -638,7 +638,7 @@ function GroupedIncidentsList({
     return null;
   }
 
-  const latestAlert = alerts[alerts.length - 1];
+  const latestAlert = alerts[0];
   const latestAlertMoment = moment(latestAlert.created_at);
 
   return (