fix: pool exhaustion and lock timeout surface as 500 instead of structured 503 (#295)

docs/module/db.md

@@ -69,6 +69,13 @@ async with lock_tables(session_maker=session_maker, tables=[User], mode=LockMode
 
 Available lock modes are defined in [`LockMode`](../reference/db.md#fastapi_toolsets.db.LockMode): `ACCESS_SHARE`, `ROW_SHARE`, `ROW_EXCLUSIVE`, `SHARE_UPDATE_EXCLUSIVE`, `SHARE`, `SHARE_ROW_EXCLUSIVE`, `EXCLUSIVE`, `ACCESS_EXCLUSIVE`.
 
+Pass `timeout` to limit how long the lock waits before giving up. On timeout, a [`LockTimeoutError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.LockTimeoutError) is raised instead of a raw database error:
+
+```python
+async with lock_tables(session_maker, [Order], timeout="2s") as session:
+    ...
+```
+
 ## Advisory locking
 
 [`advisory_lock`](../reference/db.md#fastapi_toolsets.db.advisory_lock) acquires a PostgreSQL session-level advisory lock. The lock is released explicitly when the context exits, regardless of whether the transaction has committed.
@@ -85,7 +92,7 @@ async with advisory_lock(session=session, key=42, nowait=True) as acquired:
     if not acquired:
         raise HTTPException(409, "Resource is locked")
 
-# Blocking with a timeout — raises DBAPIError if not acquired in time
+# Blocking with a timeout — raises LockTimeoutError if not acquired in time
 async with advisory_lock(session=session, key=42, timeout="5s"):
     ...
 

docs/module/exceptions.md

@@ -39,6 +39,8 @@ It also patches `app.openapi()` to replace the default Pydantic 422 schema with
 | [`NoSearchableFieldsError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.NoSearchableFieldsError) | 400 | No Searchable Fields |
 | [`InvalidFacetFilterError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.InvalidFacetFilterError) | 400 | Invalid Facet Filter |
 | [`InvalidOrderFieldError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.InvalidOrderFieldError) | 422 | Invalid Order Field |
+| [`PoolExhaustedError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.PoolExhaustedError) | 503 | Service Unavailable |
+| [`LockTimeoutError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.LockTimeoutError) | 503 | Service Unavailable |
 
 ### Per-instance overrides
 

docs/reference/exceptions.md

@@ -15,6 +15,8 @@ from fastapi_toolsets.exceptions import (
     InvalidSearchColumnError,
     InvalidFacetFilterError,
     InvalidOrderFieldError,
+    PoolExhaustedError,
+    LockTimeoutError,
     generate_error_responses,
     init_exceptions_handlers,
 )
@@ -38,6 +40,10 @@ from fastapi_toolsets.exceptions import (
 
 ## ::: fastapi_toolsets.exceptions.exceptions.InvalidOrderFieldError
 
+## ::: fastapi_toolsets.exceptions.exceptions.PoolExhaustedError
+
+## ::: fastapi_toolsets.exceptions.exceptions.LockTimeoutError
+
 ## ::: fastapi_toolsets.exceptions.exceptions.generate_error_responses
 
 ## ::: fastapi_toolsets.exceptions.handler.init_exceptions_handlers