Power BI Refresh Error:
250002

What does this error mean?

The Python connector attempted to use a Snowflake connection that has already been closed. This happens when a connection object is reused after an explicit close() call, a session timeout, or a connection pool reclamation.

Common causes

• 1Calling cursor.execute() or connection methods after connection.close() has been called
• 2A context manager (with statement) closes the connection at the end of its block and code outside reuses it
• 3Connection pool returning a stale or already-closed connection
• 4Session lifetime expired (STATEMENT_TIMEOUT or SESSION_POLICY) invalidating the connection mid-use
• 5Multi-threaded code sharing a single connection object without synchronization

How to fix it

1. 1Ensure connection.close() is only called after all operations on that connection are complete.
2. 2Use context managers (with snowflake.connector.connect(...) as conn) and do all work inside the block.
3. 3For connection pools, add connection validation (e.g., conn.is_still_running()) before reuse.
4. 4If using SQLAlchemy, enable pool_pre_ping=True to test connections before checkout.
5. 5In multi-threaded code, create a separate connection per thread rather than sharing one instance.

Frequently asked questions

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