diff options
Diffstat (limited to 'lib/sqlalchemy/events.py')
| -rw-r--r-- | lib/sqlalchemy/events.py | 25 |
1 files changed, 21 insertions, 4 deletions
diff --git a/lib/sqlalchemy/events.py b/lib/sqlalchemy/events.py index bbba00148..8fde0114c 100644 --- a/lib/sqlalchemy/events.py +++ b/lib/sqlalchemy/events.py @@ -775,7 +775,23 @@ class ConnectionEvents(event.Events): the scope of this hook; the rollback of the per-statement transaction also occurs after the hook is called. - The user-defined event handler has two options for replacing + For the common case of detecting a "disconnect" situation which + is not currently handled by the SQLAlchemy dialect, the + :attr:`.ExceptionContext.is_disconnect` flag can be set to True which + will cause the exception to be considered as a disconnect situation, + which typically results in the connection pool being invalidated:: + + @event.listens_for(Engine, "handle_error") + def handle_exception(context): + if isinstance(context.original_exception, pyodbc.Error): + for code in ( + '08S01', '01002', '08003', + '08007', '08S02', '08001', 'HYT00', 'HY010'): + + if code in str(context.original_exception): + context.is_disconnect = True + + A handler function has two options for replacing the SQLAlchemy-constructed exception into one that is user defined. It can either raise this new exception directly, in which case all further event listeners are bypassed and the @@ -813,9 +829,10 @@ class ConnectionEvents(event.Events): return MySpecialException("failed", cause=context.chained_exception) - Handlers that return ``None`` may remain within this chain; the - last non-``None`` return value is the one that continues to be - passed to the next handler. + Handlers that return ``None`` may be used within the chain; when + a handler returns ``None``, the previous exception instance, + if any, is maintained as the current exception that is passed onto the + next handler. When a custom exception is raised or returned, SQLAlchemy raises this new exception as-is, it is not wrapped by any SQLAlchemy |