Delete duplicate direct paging integrations (#3412)

# What this PR does

Deletes duplicate direct paging integrations (i.e. keeps only the first
direct paging integration per team).
Also adds a unique constraint that will make such duplicates impossible
at the DB level.

## Which issue(s) this PR fixes

Related to https://github.com/grafana/oncall-private/issues/2302

## 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

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Fixed
+
+- Delete duplicate direct paging integrations by @vadimkerr ([#3412](https://github.com/grafana/oncall/pull/3412))
+
 ## v1.3.65 (2023-11-29)
 
 ### Added

engine/apps/alerts/migrations/0041_alertreceivechannel_unique_direct_paging_integration_per_team.py

@@ -0,0 +1,56 @@
+# Generated by Django 4.2.7 on 2023-11-28 10:45
+import logging
+
+from django.db import migrations, models
+from django.utils import timezone
+
+logger = logging.getLogger(__name__)
+
+
+def delete_duplicate_direct_paging_integrations(apps, schema_editor):
+    AlertReceiveChannel = apps.get_model("alerts", "AlertReceiveChannel")
+
+    # get (organization_id, team_id) pairs for teams that have more than one direct paging integration
+    duplicate_rows = AlertReceiveChannel.objects.values_list(
+        "organization_id", "team_id"
+    ).annotate(count=models.Count("id")).filter(integration="direct_paging", deleted_at__isnull=True, count__gt=1)
+
+    for organization_id, team_id, _ in duplicate_rows:
+        # get the first direct paging integration for the team (the one we want to keep)
+        first_direct_paging_integration = AlertReceiveChannel.objects.filter(
+            organization_id=organization_id,
+            team_id=team_id,
+            integration="direct_paging",
+            deleted_at__isnull=True,
+        ).order_by("id").first()
+
+        if first_direct_paging_integration is None:
+            continue
+
+        # delete all other direct paging integrations for the team (except the first one)
+        num_deleted = AlertReceiveChannel.objects.filter(
+            organization_id=organization_id,
+            team_id=team_id,
+            integration="direct_paging",
+            deleted_at__isnull=True,
+        ).exclude(id=first_direct_paging_integration.id).update(deleted_at=timezone.now())
+
+        logger.info(
+            f"Deleted {num_deleted} duplicate direct paging integrations for team ({organization_id}, {team_id}), "
+            f"keeping only one direct paging integration for team: {first_direct_paging_integration.id}."
+        )
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('alerts', '0040_alertreceivechannel_alert_group_labels_custom_and_more'),
+    ]
+
+    operations = [
+        migrations.RunPython(delete_duplicate_direct_paging_integrations, migrations.RunPython.noop),
+        migrations.AddConstraint(
+            model_name='alertreceivechannel',
+            constraint=models.UniqueConstraint(models.F('organization'), models.Case(models.When(team=None, then=0), default=models.F('team'), output_field=models.BigIntegerField()), models.Case(models.When(deleted_at__isnull=True, then=True), default=None), models.Case(models.When(integration='direct_paging', then=True), default=None), name='unique_direct_paging_integration_per_team'),
+        ),
+    ]

engine/apps/alerts/models/alert_receive_channel.py

@@ -8,7 +8,7 @@ from celery import uuid as celery_uuid
 from django.conf import settings
 from django.core.validators import MinLengthValidator
 from django.db import models, transaction
-from django.db.models import Q
+from django.db.models import BigIntegerField, Case, F, Q, When
 from django.db.models.signals import post_save
 from django.dispatch import receiver
 from django.utils import timezone
@@ -215,6 +215,21 @@ class AlertReceiveChannel(IntegrationOptionsMixin, MaintainableObject):
     alert_group_labels_template: str | None = models.TextField(null=True, default=None)
     """Stores a Jinja2 template for "advanced label templating" for alert group labels."""
 
+    class Meta:
+        constraints = [
+            # This constraint ensures that there's at most one active direct paging integration per team
+            # This should work with SQLite, PostgreSQL and MySQL >= 8.0.13.
+            # From the docs: Functional indexes are ignored with MySQL < 8.0.13 and MariaDB as neither supports them.
+            # https://docs.djangoproject.com/en/4.2/ref/models/constraints/#expressions
+            models.UniqueConstraint(
+                F("organization"),
+                Case(When(team=None, then=0), default=F("team"), output_field=BigIntegerField()),
+                Case(When(deleted_at__isnull=True, then=True), default=None),
+                Case(When(integration="direct_paging", then=True), default=None),
+                name="unique_direct_paging_integration_per_team",
+            )
+        ]
+
     def __str__(self):
         short_name_with_emojis = emojize(self.short_name, language="alias")
         return f"{self.pk}: {short_name_with_emojis}"

engine/apps/alerts/tests/test_alert_receiver_channel.py

@@ -2,6 +2,7 @@ from unittest import mock
 from unittest.mock import patch
 
 import pytest
+from django.db import IntegrityError
 from django.urls import reverse
 
 from apps.alerts.models import AlertReceiveChannel
@@ -229,3 +230,20 @@ def test_delete_duplicate_names(make_organization, make_alert_receive_channel):
     for _ in range(2):
         make_alert_receive_channel(organization, verbal_name="duplicate")
     organization.alert_receive_channels.all().delete()
+
+
+@pytest.mark.django_db
+def test_create_duplicate_direct_paging_integrations(make_organization, make_team, make_alert_receive_channel):
+    """Check that it's not possible to have more than one active direct paging integration per team."""
+
+    organization = make_organization()
+    team = make_team(organization)
+    make_alert_receive_channel(organization, team=team, integration=AlertReceiveChannel.INTEGRATION_DIRECT_PAGING)
+
+    with pytest.raises(IntegrityError):
+        arc = AlertReceiveChannel(
+            organization=organization,
+            team=team,
+            integration=AlertReceiveChannel.INTEGRATION_DIRECT_PAGING,
+        )
+        super(AlertReceiveChannel, arc).save()  # bypass the custom save method, so that IntegrityError is raised

engine/apps/api/tests/test_alert_receive_channel.py

@@ -852,35 +852,6 @@ def test_update_alert_receive_channels_direct_paging(
     assert response.json()["detail"] == AlertReceiveChannel.DuplicateDirectPagingError.DETAIL
 
 
-@pytest.mark.django_db
-def test_delete_alert_receive_channel_direct_paging_duplicate(
-    make_organization_and_user_with_plugin_token, make_team, make_alert_receive_channel, make_user_auth_headers
-):
-    """Check that it's possible to delete direct paging integration even if there is a duplicate for the team."""
-    organization, user, token = make_organization_and_user_with_plugin_token()
-    integration = make_alert_receive_channel(
-        organization, integration=AlertReceiveChannel.INTEGRATION_DIRECT_PAGING, team=None
-    )
-
-    # Create a team, add direct paging integration to it, then delete the team.
-    # There will be 2 direct paging integrations for the team "No team" as a result.
-    team = make_team(organization)
-    make_alert_receive_channel(organization, integration=AlertReceiveChannel.INTEGRATION_DIRECT_PAGING, team=team)
-    team.delete()
-    assert (
-        organization.alert_receive_channels.filter(
-            integration=AlertReceiveChannel.INTEGRATION_DIRECT_PAGING, team=None
-        ).count()
-        == 2
-    )
-
-    client = APIClient()
-    url = reverse("api-internal:alert_receive_channel-detail", kwargs={"pk": integration.public_primary_key})
-    response = client.delete(url, **make_user_auth_headers(user, token))
-
-    assert response.status_code == status.HTTP_204_NO_CONTENT
-
-
 @pytest.mark.django_db
 def test_start_maintenance_integration(
     make_user_auth_headers,