Report num. annotations marked deleted to New Relic

h/tasks/cleanup.py

@@ -1,6 +1,9 @@
 # pylint: disable=no-member # Instance of 'Celery' has no 'request' member
 from datetime import datetime
 
+import newrelic
+from sqlalchemy import func, select
+
 from h import models
 from h.celery import celery, get_task_logger
 
@@ -12,6 +15,33 @@ def purge_deleted_annotations():
     celery.request.find_service(name="annotation_delete").bulk_delete()
 
 
+@celery.task
+def report_num_deleted_annotations():
+    """
+    Report the number of deleted annotations to New Relic.
+
+    Send a custom metric to New Relic that counts the number of annotations
+    that have been marked as deleted in the database but not yet "purged" (i.e.
+    actually deleted) from the database by the purge_deleted_annotations() task
+    above
+
+    This is so that we can set a New Relic alert based on this metric so that
+    we can know if the purge_deleted_annotations() task is unable to keep up
+    (since it only deletes up to a limited number of annotations per task run)
+    and we're failing to actually purge data from the database when users ask
+    us to. Otherwise annotations could be marked as deleted but never actually
+    purged and we'd never know.
+    """
+    newrelic.agent.record_custom_metric(
+        "Custom/Annotations/MarkedAsDeleted",
+        celery.request.db.scalar(
+            select(
+                func.count(models.Annotation.id)  # pylint:disable=not-callable
+            ).where(models.Annotation.deleted.is_(True))
+        ),
+    )
+
+
 @celery.task
 def purge_expired_auth_tickets():
     celery.request.db.query(models.AuthTicket).filter(

tests/unit/h/tasks/cleanup_test.py

@@ -10,6 +10,7 @@
     purge_expired_authz_codes,
     purge_expired_tokens,
     purge_removed_features,
+    report_num_deleted_annotations,
 )
 
 
@@ -21,6 +22,21 @@ def test_purge(self, annotation_delete_service):
         annotation_delete_service.bulk_delete.assert_called_once()
 
 
+@pytest.mark.usefixtures("celery")
+class TestReportNumDeletedAnnotations:
+    def test_report_num_deleted_annotations(self, factories, newrelic):
+        # Annotations marked as deleted, these should be counted.
+        factories.Annotation.create_batch(2, deleted=True)
+        # An annotation not marked as deleted, this should not be counted.
+        factories.Annotation.create()
+
+        report_num_deleted_annotations()
+
+        newrelic.agent.record_custom_metric.assert_called_once_with(
+            "Custom/Annotations/MarkedAsDeleted", 2
+        )
+
+
 @pytest.mark.usefixtures("celery")
 class TestPurgeExpiredAuthTickets:
     def test_it_removes_expired_tickets(self, db_session, factories):
@@ -141,3 +157,8 @@ def celery(patch, pyramid_request):
     cel = patch("h.tasks.cleanup.celery", autospec=False)
     cel.request = pyramid_request
     return cel
+
+
+@pytest.fixture(autouse=True)
+def newrelic(mocker):
+    return mocker.patch("h.tasks.cleanup.newrelic")