v.21.3Improvement

MySQL Dictionary Source Enhances Retry Mechanism for Connection Failures

MySQL dictionary source will now retry unexpected connection failures (Lost connection to MySQL server during query) which sometimes happen on SSL/TLS connections. #21237 (Alexander Kazakov).
The MySQL dictionary source now automatically retries on unexpected connection failures, such as "Lost connection to MySQL server during query", improving stability during SSL/TLS connections.

Why it matters

This feature addresses intermittent connection failures with MySQL dictionaries in ClickHouse, particularly during SSL/TLS sessions. It enhances reliability by retrying queries when unexpected disconnections occur, reducing query errors and improving user experience.

How to use it

This retry behavior is enabled by default for MySQL dictionaries in ClickHouse. Users do not need to take additional steps; ClickHouse will automatically retry queries if a connection loss is detected during dictionary data fetching.