Addressing MySQL Error 2023 – CR_PROBE_SLAVE_HOSTS: Resolving Issues with SHOW SLAVE HOSTS

When managing a MySQL replication setup, you might come across Error 2023, which is associated with the SHOW SLAVE HOSTS command. This error can occur when there are issues with the replication environment, particularly with retrieving information about the slave hosts from the master server.

Understanding the Error

Error 2023 is specifically tied to the replication aspect of MySQL:


This error indicates that the master server encountered an issue when attempting to display the slave hosts connected to it.

Diagnosing the Issue

To effectively diagnose and troubleshoot this error, consider the following steps:

1. Check Replication Configuration

Ensure that replication is correctly set up on all slave servers. Each slave should have a unique server-id set in the MySQL configuration file (my.cnf or my.ini), and the master must have binary logging enabled with a server-id as well.

2. Verify Master Configuration

On the master server, ensure that the report_host, report_port, report_user, and report_password options are correctly configured if they are being used. These settings allow the master to recognize and report on slave hosts.

3. Inspect Slave Host Connectivity

Check that each slave can connect to the master server. Network issues, incorrect hostnames, or port configurations can cause connectivity problems.

4. Review User Privileges

The user account used to execute the SHOW SLAVE HOSTS command must have the REPLICATION SLAVE privilege. Verify the user’s privileges with:

SHOW GRANTS FOR 'replication_user'@'slave_host';

Replace replication_user and slave_host with the appropriate user and host for your setup.

5. Examine Slave Registration

Slaves register themselves with the master only if the report_host system variable is set on the slaves. Check that this variable is set correctly on each slave:

SHOW VARIABLES LIKE 'report_host';

If it’s not set, add it to the slave’s configuration file and restart the MySQL service.

6. Confirm Slave Status

On each slave, run the SHOW SLAVE STATUS command to ensure that the slave is correctly connected and replicating from the master:


Look for Slave_IO_Running and Slave_SQL_Running status variables to be set to Yes.

7. Check for Error Messages

Look for any additional error messages in the MySQL error log on both the master and slave servers. These messages can provide clues as to what might be causing the issue with the SHOW SLAVE HOSTS command.

8. Restart Replication Threads

If configuration settings were changed on the slaves, you may need to restart the replication threads. Stop and start the slave threads using:


9. Use Alternative Methods for Host Information

If the SHOW SLAVE HOSTS command continues to be problematic, consider using alternative methods to gather information about slave hosts, such as querying the performance_schema.replication_connection_status and performance_schema.replication_group_member_stats tables, if available.

By following these steps, you should be able to diagnose and correct MySQL Error 2023 related to the SHOW SLAVE HOSTS command. Proper configuration of both master and slave servers, along with the correct user privileges, are key to resolving this issue and ensuring a healthy replication setup.

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