Fix message is too big exception for mobile push notification (#3556)

# What this PR does
Adds limit for alert title length in mobile app push notifications
## Which issue(s) this PR fixes
https://github.com/grafana/oncall-private/issues/2375
## Checklist

- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

CHANGELOG.md

@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Add error code for mobile push notification logs when device is not set up @Ferril ([#3554](https://github.com/grafana/oncall/pull/3554))
 
+### Fixed
+
+- Fix issue when mobile push notification message is too big @Ferril ([#3556](https://github.com/grafana/oncall/pull/3556)
+
 ## v1.3.77 (2023-12-11)
 
 ### Fixed

engine/apps/mobile_app/alert_rendering.py

@@ -10,9 +10,14 @@ class AlertMobileAppTemplater(AlertTemplater):
 
 
 def get_push_notification_subtitle(alert_group):
+    MAX_ALERT_TITLE_LENGTH = 200
     alert = alert_group.alerts.first()
     templated_alert = AlertMobileAppTemplater(alert).render()
     alert_title = str_or_backup(templated_alert.title, "Alert Group")
+    # limit alert title length to prevent FCM `message is too big` exception
+    # https://firebase.google.com/docs/cloud-messaging/concept-options#notifications_and_data_messages
+    if len(alert_title) > MAX_ALERT_TITLE_LENGTH:
+        alert_title = f"{alert_title[:MAX_ALERT_TITLE_LENGTH]}..."
 
     status_verbose = "Firing"  # TODO: we should probably de-duplicate this text
     if alert_group.resolved:

engine/apps/mobile_app/tests/tasks/test_new_alert_group.py

@@ -2,7 +2,9 @@ from unittest.mock import patch
 
 import pytest
 
+from apps.alerts.incident_appearance.templaters.alert_templater import TemplatedAlert
 from apps.base.models import UserNotificationPolicy, UserNotificationPolicyLogRecord
+from apps.mobile_app.alert_rendering import AlertMobileAppTemplater, get_push_notification_subtitle
 from apps.mobile_app.models import FCMDevice, MobileAppUserSettings
 from apps.mobile_app.tasks.new_alert_group import _get_fcm_message, notify_user_about_new_alert_group
 
@@ -175,3 +177,37 @@ def test_fcm_message_user_settings_critical_override_dnd_disabled(
     apns_sound = message.apns.payload.aps.sound
     assert apns_sound.critical is False
     assert message.apns.payload.aps.custom_data["interruption-level"] == "time-sensitive"
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    "alert_title",
+    [
+        "Some short title",
+        "Some long title" * 100,
+    ],
+)
+def test_get_push_notification_subtitle(
+    alert_title,
+    make_organization_and_user,
+    make_alert_receive_channel,
+    make_alert_group,
+    make_alert,
+):
+    MAX_ALERT_TITLE_LENGTH = 200
+    organization, user = make_organization_and_user()
+    alert_receive_channel = make_alert_receive_channel(organization=organization)
+    alert_group = make_alert_group(alert_receive_channel)
+    make_alert(alert_group=alert_group, title=alert_title, raw_request_data={"title": alert_title})
+    expected_alert_title = (
+        f"{alert_title[:MAX_ALERT_TITLE_LENGTH]}..." if len(alert_title) > MAX_ALERT_TITLE_LENGTH else alert_title
+    )
+    expected_result = (
+        f"#1 {expected_alert_title}\n" + f"via {alert_group.channel.short_name}" + "\nStatus: Firing, alerts: 1"
+    )
+    templated_alert = TemplatedAlert()
+    templated_alert.title = alert_title
+    with patch.object(AlertMobileAppTemplater, "render", return_value=templated_alert):
+        result = get_push_notification_subtitle(alert_group)
+    assert len(expected_alert_title) <= MAX_ALERT_TITLE_LENGTH + 3
+    assert result == expected_result