The processlist method for searching for replicas can also be unreliable if hostname is longer than 60 characters in older MySQL versions
General
Escalation
General
Escalation
Description
As per bug https://bugs.mysql.com/bug.php?id=63814, host name is limited to 60 characters for older versions MySQL 5.7 and MySQL 8.0.16 and below. However, the maximum length of a hostname is 255 characters.
This becomes a problem when pt-table-checksum attempts to look for replicas via SHOW PROCESSLIST on older versions with long host names because the tool won’t be able to find them when the host names are truncated.
As per bug https://bugs.mysql.com/bug.php?id=63814, host name is limited to 60 characters for older versions MySQL 5.7 and MySQL 8.0.16 and below. However, the maximum length of a hostname is 255 characters.
This becomes a problem when pt-table-checksum attempts to look for replicas via SHOW PROCESSLIST on older versions with long host names because the tool won’t be able to find them when the host names are truncated.
It would be best to document this limitation in https://docs.percona.com/percona-toolkit/pt-table-checksum.html to aid in troubleshooting if users encounter the same issue in the future.