Skip to main content

MySQL troubleshooting

This document provides solutions for issues that may occur when using the MySQL service.

Unable to connect between client and MySQL instance in VPC​

If you are unable to connect to port 3306 or 3307 of the MySQL instance (cluster), consider the following common causes:

Check availability status​

A newly created DB instance will remain in the Creating state until it is ready. You can connect to it once its status changes to Available.
Refer to Instance Group Availability Status for more details.

Instance Group StatusAvailabilityDescription
AVAILABLEREADYAll configurations are complete

Test connection to DB instance​

  1. On Linux or Unix, you can test connectivity from a terminal using the command below. Replace "DB-INSTANCE-ENDPOINT" and "PORT" with your actual endpoint and port.

    Test Instance Connection
    nc -vz "DB-INSTANCE-ENDPOINT" "PORT"

    Example:

    Sample Test
    ubuntu@host-172-16-3-252:~$ nc -vz "DB-INSTANCE-ENDPOINT" "PORT"
    Connection to "DB-INSTANCE-ENDPOINT" (172.16.3.154) "PORT" port [tcp/mysql] succeeded!

  2. On Windows, you can test the connection to the DB instance using Telnet.

    Telnet is supported only for connection testing purposes. If the connection is successful, no message will be displayed. If the connection fails, an error message will appear.

    Connection test
    C:\Users\Administrator>telnet "DB-INSTANCE-ENDPOINT" "PORT"
    Connecting to "DB-INSTANCE-ENDPOINT"...Could not open connection to the host, on port "PORT": Connect failed

Lost DB instance owner password​

If you have lost the owner password for the DB instance, please contact the KakaoCloud Helpdesk.

CategoryDescription
{MySQL-ADMIN-PASSWORD}⚠️ The admin password can be changed after the database has started.
⚠️ Once changed by the user, the admin password cannot be retrieved.

DB instance storage shortage​

If the storage capacity is insufficient, DB instance operations may not function properly.

▶️ Solution: Expand the storage using the volume expansion feature to keep the DB instance's storage usage below 80%. Below is a sample command and return message.

Sample Command Failure
mysql> create table test(test_name varchar(20), test_age int);
"No response"

Unable to view slow queries (Monitoring > Log Explorer)​

In the MySQL service, slow queries are stored as files and can be viewed via Monitoring > Log Explorer.

Logs older than 5 days​

By default, Log Explorer only retains and displays slow query log data for up to 5 days. Logs older than 5 days cannot be accessed.
▶️ Solution: If you need to retain logs for more than 5 days, change the log storage location from file to table using Stored Procedures.

info

If you are unable to access logs within 5 days, please contact the KakaoCloud Helpdesk.

SSH error message: Access denied​

ERROR 1044 (42000): Access denied for user 'user'@'%' to database 'database'​

This error occurs when creating a user or assigning privileges.

MySQL CLI
mysql> CREATE USER 'user'@'%' IDENTIFIED BY '1234';
mysql> GRANT ALL PRIVILEGES ON user.* TO 'user'@'%';
ERROR 1044 (42000): Access denied for user 'admin'@'%' to database 'database'

▶️ Solution: Manage accounts and privileges using the default stored procedures provided by KakaoCloud MySQL. For detailed instructions, please refer to Account Setup and Privileges.