refactor(payments): enhance payment processing logic and error handling

Refactor the `process_successful_payment` function to improve the handling of payment statuses during processing. Introduce a new method to atomically claim payments for processing and rollback payment statuses in case of activation failures. Enhance logging for various scenarios, including payment status checks and rollback actions, to provide clearer insights into payment processing flows. This improves the robustness and reliability of the payment handling logic.

bot/handlers/user/payment.py

@@ -59,6 +59,7 @@ async def process_successful_payment(session: AsyncSession, bot: Bot,
         return False
 
     db_user = None
+    payment_before_update = None
     try:
         user_id = int(user_id_str)
         subscription_months = float(subscription_months_str or 0)
@@ -213,7 +214,6 @@ async def process_successful_payment(session: AsyncSession, bot: Bot,
                 f"Missing provider payment id in successful YooKassa webhook for payment {payment_db_id}"
             )
 
-        payment_before_update = None
         if payment_db_id is not None:
             payment_before_update = await payment_dal.get_payment_by_db_id(
                 session,
@@ -227,18 +227,39 @@ async def process_successful_payment(session: AsyncSession, bot: Bot,
                 )
                 return True
 
-        marked = await payment_dal.mark_provider_payment_succeeded_once(
+        claimed_for_processing = await payment_dal.mark_provider_payment_processing_once(
             session,
             payment_db_id,
             provider_payment_id,
+            expected_status_prefix="pending",
         )
-        if not marked:
+        if not claimed_for_processing:
+            payment_after_claim = await payment_dal.get_payment_by_db_id(
+                session,
+                payment_db_id,
+            )
+            if payment_after_claim and payment_after_claim.status == "succeeded":
                 logging.info(
-                "YooKassa webhook: payment %s already processed atomically",
+                    "YooKassa webhook ignored: payment %s already succeeded after claim attempt",
                     payment_db_id,
                 )
                 return True
 
+            # Another transaction is processing this payment now.
+            if payment_after_claim and payment_after_claim.status == "processing":
+                logging.info(
+                    "YooKassa webhook: payment %s is already being processed by another worker",
+                    payment_db_id,
+                )
+                return False
+
+            logging.warning(
+                "YooKassa webhook: payment %s cannot be claimed for processing (status=%s)",
+                payment_db_id,
+                payment_after_claim.status if payment_after_claim else None,
+            )
+            return False
+
         should_send_lknpd_receipt = bool(
             lknpd_service
             and lknpd_service.configured
@@ -295,7 +316,9 @@ async def process_successful_payment(session: AsyncSession, bot: Bot,
                     logging.exception("Failed to persist multi-card YooKassa method from webhook")
         except Exception:
             logging.exception("Failed to persist YooKassa payment method from webhook")
+
         months_for_activation = int(subscription_months) if sale_mode != "traffic" else 0
+        try:
             activation_details = await subscription_service.activate_subscription(
                 session,
                 user_id,
@@ -307,13 +330,44 @@ async def process_successful_payment(session: AsyncSession, bot: Bot,
                 sale_mode=sale_mode,
                 traffic_gb=traffic_amount_gb if sale_mode == "traffic" else None,
             )
+        except Exception:
+            previous_status = payment_before_update.status if payment_before_update else "pending_yookassa"
+            await payment_dal.rollback_provider_payment_processing(
+                session,
+                payment_db_id,
+                rollback_status=previous_status,
+                provider_payment_id=provider_payment_id,
+            )
+            logging.exception(
+                "Failed to activate subscription for payment %s; rolled back payment status for retry",
+                payment_db_id,
+            )
+            return False
 
         if not activation_details or not activation_details.get('end_date'):
             logging.error(
                 f"Failed to activate subscription for user {user_id} after payment {yk_payment_id_from_hook}"
             )
-            raise Exception(
+            previous_status = payment_before_update.status if payment_before_update else "pending_yookassa"
-                f"Subscription Error: Failed to activate for user {user_id}")
+            await payment_dal.rollback_provider_payment_processing(
+                session,
+                payment_db_id,
+                rollback_status=previous_status,
+                provider_payment_id=provider_payment_id,
+            )
+            return False
+
+        marked = await payment_dal.mark_provider_payment_succeeded_once(
+            session,
+            payment_db_id,
+            provider_payment_id,
+        )
+        if not marked:
+            logging.warning(
+                "YooKassa webhook: payment %s could not be atomically marked succeeded after activation",
+                payment_db_id,
+            )
+            return False
 
         base_subscription_end_date = activation_details['end_date']
         final_end_date_for_user = base_subscription_end_date

db/alembic_runner.py

@@ -11,6 +11,7 @@ from sqlalchemy.ext.asyncio import AsyncEngine
 from config.settings import Settings
 
 
+import os
 _BASELINE_REVISION = "0001_initial_schema"
 
 

db/dal/payment_dal.py

@@ -208,6 +208,80 @@ async def mark_provider_payment_succeeded_once(
     return updated
 
 
+async def mark_provider_payment_processing_once(
+        session: AsyncSession,
+        payment_db_id: int,
+        provider_payment_id: str,
+        expected_status_prefix: Optional[str] = None) -> bool:
+    """Atomically claim payment for processing exactly once.
+
+    Returns True only when status is changed from a non-terminal state to
+    "processing". This prevents duplicate activation when concurrent
+    webhooks arrive for the same payment.
+    """
+    conditions = [
+        Payment.payment_id == payment_db_id,
+        Payment.status != "succeeded",
+        Payment.status != "processing",
+    ]
+    if expected_status_prefix:
+        conditions.append(Payment.status.like(f"{expected_status_prefix}%"))
+
+    stmt = (
+        update(Payment)
+        .where(*conditions)
+        .values(
+            status="processing",
+            provider_payment_id=provider_payment_id,
+            updated_at=func.now(),
+        )
+    )
+    result = await session.execute(stmt)
+    updated = (result.rowcount or 0) > 0
+    if updated:
+        logging.info(
+            "Payment record %s atomically marked as processing (provider id %s).",
+            payment_db_id,
+            provider_payment_id,
+        )
+    return updated
+
+
+async def rollback_provider_payment_processing(
+        session: AsyncSession,
+        payment_db_id: int,
+        rollback_status: str,
+        provider_payment_id: Optional[str] = None) -> bool:
+    """Atomically rollback temporary processing status.
+
+    Returns True only if payment is currently in "processing" state.
+    """
+    values = {
+        "status": rollback_status,
+        "updated_at": func.now(),
+    }
+    if provider_payment_id:
+        values["provider_payment_id"] = provider_payment_id
+
+    stmt = (
+        update(Payment)
+        .where(
+            Payment.payment_id == payment_db_id,
+            Payment.status == "processing",
+        )
+        .values(**values)
+    )
+    result = await session.execute(stmt)
+    updated = (result.rowcount or 0) > 0
+    if updated:
+        logging.info(
+            "Payment record %s rolled back from processing to %s.",
+            payment_db_id,
+            rollback_status,
+        )
+    return updated
+
+
 async def update_payment_discount_info(
         session: AsyncSession,
         payment_db_id: int,