"The slave IO thread stops" Displayed During the MySQL Primary-Secondary Replication Verification

Symptom

The message "The slave I/O thread stops because master and slave have equal MySQL server UUIDs; these UUIDs must be different for replication to work." is displayed after you log in to the secondary database and check the status of the secondary database.

Key Process and Cause Analysis

In the primary-secondary replication architecture of MySQL, each instance has a unique UUID, which is stored in the auto.cnf file in the data directory. If the primary and secondary instances use the same UUID in the replication architecture, the replication fails. Therefore, ensure that the UUID of each MySQL instance is unique.

Conclusion and Solution

To solve this problem, stop the standby database instance, delete the auto.cnf file (which stores the UUID information of the instance) in the data directory of the standby database instance, and start the standby database instance. In this case, a new auto.cnf file that contains a new UUID is generated for the standby database.

1. Shut down the secondary and primary databases in sequence.
2. Run the following command on the primary and secondary databases to delete the auto.cnf file:

   cd /data/mysql/data
   rm -rf auto.cnf

3. Start the primary and secondary databases in sequence.
4. Log in to the secondary database and run the following command to start the replication process on the secondary server:

   start slave;

5. Check the MySQL primary-secondary replication status again.

   SHOW SLAVE STATUS;