# What this PR does
Sometimes plugin sync fails with the following exception:
```
Cannot delete or update a parent row: a foreign key constraint fails (`schedules_oncallschedule`, CONSTRAINT `alerts_oncallschedul_team_id_4e633f4b_fk_user_mana` FOREIGN KEY (`team_id`) REFERENCES `user_management_team` (`id`))'
```
How to reproduce:
1. Create a new Grafana team
2. Create two schedules with different types (e.g. ICal and Web) and
assign both schedules to the new team
3. Delete the team in Grafana
4. Trigger plugin sync, the sync will fail with the exception above
This happens because the `OnCallSchedule` Django model is a polymorphic
model and there's a [known
bug](https://github.com/django-polymorphic/django-polymorphic/issues/229)
in `django-polymorphic` with deleting related objects when using
`SET_NULL` and `CASCADE`. This PR adds non-polymorphic versions of
`SET_NULL` and `CASCADE` to use in schedule FKs as per this
[comment](https://github.com/django-polymorphic/django-polymorphic/issues/229#issuecomment-398434412).
This also applies to two other schedule FKs: `organization` and
`user_group`, which are not working properly as well.
## 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)
# What this PR does
This PR:
- modifies the `check_escalation_finished_task` celery task to:
- do stricter escalation validation based on the alert group's
escalation snapshot (see the `audit_alert_group_escalation` method in
`engine/apps/alerts/tasks/check_escalation_finished.py` for the
validation logic)
- use a read-only database for querying alert-groups if one is
configured, otherwise use the "default" one
- ping a configurable heartbeat (new env var
`ALERT_GROUP_ESCALATION_AUDITOR_CELERY_TASK_HEARTBEAT_URL` added)
- increase the task frequency from every 10 to every 13 minutes (this
can be configured via an env variable)
- adds public documentation on how to configure this auditor task
- modifies the local celery startup command to properly take into
consideration all celery related env vars (similar to the ones we use in
`engine/celery_with_exporter.sh`; this made it easier to enable `celery
beat` locally for testing)
- removes the following code:
- removes references to `AlertGroup.estimate_escalation_finish_time` and
marks the model field as deprecated using the [`django-deprecate-fields`
library](https://pypi.org/project/django-deprecate-fields/). This field
was only used for the previous version of this validation task
- `EscalationSnapshotMixin.calculate_eta_for_finish_escalation` was only
used to calculate the value for
`AlertGroup.estimate_escalation_finish_time`
- `calculate_escalation_finish_time` celery task
## Which issue(s) this PR fixes
https://github.com/grafana/oncall-private/issues/1558
## Checklist
- [x] Tests updated
- [x] Documentation added
- [x] `CHANGELOG.md` updated
# What this PR does
This is a minor refactor before implementing
https://github.com/grafana/oncall-private/issues/1558.
Additionally, it cleans up a few spots where we do this:
```
# Re-take in case we are in the readonly db context.
```
We currently don't read anything from a read-only database, so this
should be not necessary.
## Checklist
- [x] Tests updated
- [ ] Documentation added (N/A)
- [ ] `CHANGELOG.md` updated (N/A)
