[PECOBLR-1655] Implemented the functionality of pool_pre_ping

[msrathore-db]

Summary

Implements is_disconnect() method to enable connection health checking and prevent "Invalid SessionHandle" errors when connections expire or are closed by the server.

Closes #47

Problem

Users experienced Invalid SessionHandle errors when connections expired or were closed by the server. SQLAlchemy's pool_pre_ping=True feature wasn't working because the dialect didn't
implement is_disconnect() to classify disconnect errors.

When connections died (either before checkout or during query execution), SQLAlchemy couldn't determine if errors were due to disconnects, leaving dead connections in the pool and causing
repeated errors.

Solution

Implements is_disconnect() method that classifies exceptions as disconnect errors, enabling both pessimistic and optimistic disconnect handling as described in SQLAlchemy's pooling documentation.

How It Works

def is_disconnect(self, e, connection, cursor):                                                                                                                                                 
    from databricks.sql.exc import InterfaceError, DatabaseError                                                                                                                                
                                                                                                                                                                                                
    # InterfaceError: Client-side errors (connection already closed)                                                                                                                            
    if isinstance(e, InterfaceError):                                                                                                                                                           
        return True                                                                                                                                                                             
                                                                                                                                                                                                
    # DatabaseError: Server-side errors with invalid handle (session expired)                                                                                                                   
    if isinstance(e, DatabaseError):                                                                                                                                                            
        error_msg = str(e).lower()                                                                                                                                                              
        return "invalid" in error_msg and "handle" in error_msg                                                                                                                                 
                                                                                                                                                                                                
    return False 

[Bidek56]

@msrathore-db This maybe a better solution.

[Bidek56]

@msrathore-db Any ETA on this PR? We are seeing sqlalchemy.exc.DatabaseError: (databricks.sql.exc.DatabaseError) Invalid SessionHandle: SessionHandle which should be resolved by this PR. Thx