Improvements to Connection auto-invalidation

handling.  If a non-disconnect error occurs,
but leads to a delayed disconnect error within error
handling (happens with MySQL), the disconnect condition
is detected.  The Connection can now also be closed
when in an invalid state, meaning it will raise "closed"
on next usage, and additionally the "close with result"
feature will work even if the autorollback in an error
handling routine fails and regardless of whether the
condition is a disconnect or not.
[ticket:2695]

1 files changed, 32 insertions, 24 deletions

diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index 6242f0816..e40af6219 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -62,6 +62,7 @@ class Connection(Connectable):
         self.__savepoint_seq = 0
         self.__branch = _branch
         self.__invalid = False
+        self.__can_reconnect = True
         if _dispatch:
             self.dispatch = _dispatch
         elif engine._has_events:
@@ -213,8 +214,8 @@ class Connection(Connectable):
     def closed(self):
         """Return True if this connection is closed."""
 
-        return not self.__invalid and '_Connection__connection' \
-                        not in self.__dict__
+        return '_Connection__connection' not in self.__dict__ \
+            and not self.__can_reconnect
 
     @property
     def invalidated(self):
@@ -232,7 +233,7 @@ class Connection(Connectable):
             return self._revalidate_connection()
 
     def _revalidate_connection(self):
-        if self.__invalid:
+        if self.__can_reconnect and self.__invalid:
             if self.__transaction is not None:
                 raise exc.InvalidRequestError(
                                 "Can't reconnect until invalid "
@@ -577,15 +578,15 @@ class Connection(Connectable):
         and will allow no further operations.
 
         """
-
         try:
             conn = self.__connection
         except AttributeError:
-            return
-        if not self.__branch:
-            conn.close()
-        self.__invalid = False
-        del self.__connection
+            pass
+        else:
+            if not self.__branch:
+                conn.close()
+            del self.__connection
+        self.__can_reconnect = False
         self.__transaction = None
 
     def scalar(self, object, *multiparams, **params):
@@ -972,13 +973,22 @@ class Connection(Connectable):
             if isinstance(e, (SystemExit, KeyboardInterrupt)):
                 raise
 
+    _reentrant_error = False
+    _is_disconnect = False
+
     def _handle_dbapi_exception(self,
                                     e,
                                     statement,
                                     parameters,
                                     cursor,
                                     context):
-        if getattr(self, '_reentrant_error', False):
+
+        if not self._is_disconnect:
+            self._is_disconnect = isinstance(e, self.dialect.dbapi.Error) and \
+                not self.closed and \
+                self.dialect.is_disconnect(e, self.__connection, cursor)
+
+        if self._reentrant_error:
             # Py3K
             #raise exc.DBAPIError.instance(statement, parameters, e,
             #                               self.dialect.dbapi.Error) from e
@@ -1006,21 +1016,10 @@ class Connection(Connectable):
                                                     e)
                 context.handle_dbapi_exception(e)
 
-            is_disconnect = isinstance(e, self.dialect.dbapi.Error) and \
-                self.dialect.is_disconnect(e, self.__connection, cursor)
-
-            if is_disconnect:
-                dbapi_conn_wrapper = self.connection
-                self.invalidate(e)
-                if not hasattr(dbapi_conn_wrapper, '_pool') or \
-                    dbapi_conn_wrapper._pool is self.engine.pool:
-                    self.engine.dispose()
-            else:
+            if not self._is_disconnect:
                 if cursor:
                     self._safe_close_cursor(cursor)
                 self._autorollback()
-                if self.should_close_with_result:
-                    self.close()
 
             if not should_wrap:
                 return
@@ -1031,7 +1030,7 @@ class Connection(Connectable):
             #                        parameters,
             #                        e,
             #                        self.dialect.dbapi.Error,
-            #                        connection_invalidated=is_disconnect) \
+            #                        connection_invalidated=self._is_disconnect) \
             #                        from e
             # Py2K
             raise exc.DBAPIError.instance(
@@ -1039,12 +1038,21 @@ class Connection(Connectable):
                                     parameters,
                                     e,
                                     self.dialect.dbapi.Error,
-                                    connection_invalidated=is_disconnect), \
+                                    connection_invalidated=self._is_disconnect), \
                                     None, sys.exc_info()[2]
             # end Py2K
 
         finally:
             del self._reentrant_error
+            if self._is_disconnect:
+                del self._is_disconnect
+                dbapi_conn_wrapper = self.connection
+                self.invalidate(e)
+                if not hasattr(dbapi_conn_wrapper, '_pool') or \
+                        dbapi_conn_wrapper._pool is self.engine.pool:
+                    self.engine.dispose()
+            if self.should_close_with_result:
+                self.close()
 
     # poor man's multimethod/generic function thingy
     executors = {