Knowledge Base

Plesk Backup finish with database warnings: Unable to back up database db_name. Error: SQLSTATE[HY000] [2002] Connection refused

Symptoms

A site backup completes with the following warnings regarding several databases:

Backup Task Mar 19, 2022 02:44 AM Details
Warning: Database "wp_database1"
Unable to make database dump. Error: Failed to exec mysqldump: Exit code: 2: mysqldump: Got error: 2013: "Lost connection to MySQL server during query" when using LOCK TABLES
Warning: Database "wp_database1"
Unable to back up database wp_database1. Error: DB query failed:
"SET sql_mode = ''"

Error: SQLSTATE[HY000] [2002] Connection refused
Warning: Database "wp_database2"
Unable to back up database wp_database3. Error: SQLSTATE[HY000] [2002] Connection refused
Warning: Database "wp_database3"
Unable to back up database wp_database3. Error: SQLSTATE[HY000] [2002] Connection refused

The following logs regarding the same databases can be found at /var/log/plesk/panel.log:

Failed to process database 'wp_database1' from domain 'example.com': MySQL error 2006: MySQL server has gone away executing query:
SHOW TABLE STATUS FROM `wp_database1`
Failed to process database 'wp_database2' from domain 'example.com': MySQL error 2006: MySQL server has gone away executing query:
SHOW TABLE STATUS FROM `wp_database2`
Failed to process database 'wp_database3' from domain 'example.com': MySQL error 2006: MySQL server has gone away executing query: 
SHOW TABLE STATUS FROM `wp_database3`
Failed to process database 'wp_database4' from domain 'example.com': MySQL error 2006: MySQL server has gone away executing query: 
SHOW TABLE STATUS FROM `wp_database4`

The solution described on this article does not solve the issue.

When the MySQL log is checked while reproducing the issue, the following errors regarding other Databases are found:

[ERROR] mysqld: Table './database5/table_name1' is marked as crashed and should be repaired
[Warning] Checking table:   './database5/table_name1'
[ERROR] mysqld: Table './other-database/table_name2' is marked as crashed and should be repaired
[Warning] Checking table:   './database5/table_name2'

Cause

One or more crashed database table causes to MySQL service to go down for a short period of time enought to results in the backup errors such as "Lost connection to MySQL server during query" or "Connection refused" or "MySQL server has gone away".