fix(events): keep registration status reads nonblocking

apps/events/checkout.py

@@ -1,6 +1,5 @@
 """Registration checkout lifecycle rules shared by API views and workers."""
 
-import logging
 from datetime import timedelta
 
 from django.db import transaction
@@ -10,16 +9,6 @@ from apps.events.models import Event, Registration
 
 
 CHECKOUT_TIMEOUT = timedelta(minutes=15)
-logger = logging.getLogger(__name__)
-
-
-def _dispatch_reconciliation(payment_id):
-    from apps.payments.tasks import reconcile_payment
-
-    try:
-        reconcile_payment.apply_async(args=(payment_id,), countdown=0)
-    except Exception:
-        logger.exception("Unable to dispatch checkout payment %s for reconciliation", payment_id)
 
 
 def mark_checkout_cancelled(registration, reason):
@@ -38,7 +27,7 @@ def mark_checkout_cancelled(registration, reason):
 
 
 def queue_checkout_reconciliation(registration):
-    """Reconcile each unresolved payment after a checkout is cancelled."""
+    """Mark no-authority attempts for review; the recovery sweep dispatches the rest."""
     from apps.payments.models import Payment
 
     payments = list(
@@ -51,11 +40,7 @@ def queue_checkout_reconciliation(registration):
         ).only("id", "authority")
     )
     for payment in payments:
-        if payment.authority:
-            transaction.on_commit(
-                lambda payment_id=payment.id: _dispatch_reconciliation(payment_id)
-            )
-        else:
+        if not payment.authority:
             # The payment request may have reached the gateway before its
             # authority was persisted. Keep it visible for review until its
             # request response arrives or an administrator resolves it.
@@ -69,7 +54,6 @@ def queue_checkout_reconciliation(registration):
             ).update(verification_manual_review_at=timezone.now())
 
 
-@transaction.atomic
 def expire_stale_registration_checkouts(*, now=None, event_id=None):
     """Release seats for new-format pending checkouts whose deadline passed.
 
@@ -85,27 +69,48 @@ def expire_stale_registration_checkouts(*, now=None, event_id=None):
     if event_id is not None:
         candidates = candidates.filter(event_id=event_id)
 
-    expired_count = 0
-    for registration_id in candidates.values_list("id", flat=True).iterator():
-        registration = (
-            Registration.objects.select_for_update()
-            .filter(pk=registration_id)
-            .first()
+    with transaction.atomic():
+        batch = list(
+            candidates.select_for_update(skip_locked=True)
+            .order_by("checkout_expires_at", "pk")[:50]
         )
-        if registration is None or registration.status != Registration.StatusChoices.PENDING:
-            continue
+        expired_count = 0
+        for registration in batch:
+            if registration.status != Registration.StatusChoices.PENDING or registration.checkout_expires_at > now:
+                continue
+            reason = (
+                Registration.CancellationReasonChoices.EVENT_CANCELLED
+                if registration.event.status == Event.StatusChoices.CANCELLED
+                else Registration.CancellationReasonChoices.CHECKOUT_EXPIRED
+            )
+            if mark_checkout_cancelled(registration, reason):
+                expired_count += 1
+                queue_checkout_reconciliation(registration)
+    return expired_count
 
+
+def expire_user_registration_checkouts(*, event, user, now):
+    """Expire only this user's rows while the caller holds the event lock."""
+    registrations = (
+        Registration.objects.select_for_update()
+        .filter(
+            event=event,
+            user=user,
+            is_deleted=False,
+            status=Registration.StatusChoices.PENDING,
+            checkout_expires_at__lte=now,
+        )
+        .order_by("pk")
+    )
+    for registration in registrations:
         reason = (
             Registration.CancellationReasonChoices.EVENT_CANCELLED
-            if registration.event.status == Event.StatusChoices.CANCELLED
+            if event.status == Event.StatusChoices.CANCELLED
             else Registration.CancellationReasonChoices.CHECKOUT_EXPIRED
         )
         if mark_checkout_cancelled(registration, reason):
-            expired_count += 1
             queue_checkout_reconciliation(registration)
 
-    return expired_count
-
 
 @transaction.atomic
 def cancel_event_checkouts(event_id):