17.1.3.4 Setting Up Replication Using GTIDs

This section describes a process for configuring and starting GTID-based replication in MySQL 8.0. This is a “cold start” procedure that assumes either that you are starting the replication master for the first time, or that it is possible to stop it; for information about provisioning replication slaves using GTIDs from a running master, see Section 17.1.3.5, “Using GTIDs for Failover and Scaleout”. For information about changing GTID mode on servers online, see Section 17.1.5, “Changing Replication Modes on Online Servers”.

The key steps in this startup process for the simplest possible GTID replication topology, consisting of one master and one slave, are as follows:

In the following example, two servers are already running as master and slave, using MySQL's binary log position-based replication protocol. If you are starting with new servers, see Section 17.1.2.3, “Creating a User for Replication” for information about adding a specific user for replication connections and Section 17.1.2.1, “Setting the Replication Master Configuration” for information about setting the server_id variable. The following examples show how to store mysqld startup options in server's option file, see Section 4.2.2.2, “Using Option Files” for more information. Alternatively you can use startup options when running mysqld.

Most of the steps that follow require the use of the MySQL root account or another MySQL user account that has the SUPER privilege. mysqladmin shutdown requires either the SUPER privilege or the SHUTDOWN privilege.

Step 1: Synchronize the servers.  This step is only required when working with servers which are already replicating without using GTIDs. For new servers proceed to Step 3. Make the servers read-only by setting the read_only system variable to ON on each server by issuing the following:

Wait for all ongoing transactions to commit or roll back. Then, allow the slave to catch up with the master. It is extremely important that you make sure the slave has processed all updates before continuing.

If you use binary logs for anything other than replication, for example to do point in time backup and restore, wait until you do not need the old binary logs containing transactions without GTIDs. Ideally, wait for the server to purge all binary logs, and wait for any existing backup to expire.

Step 2: Stop both servers.  Stop each server using mysqladmin as shown here, where username is the user name for a MySQL user having sufficient privileges to shut down the server:

shell> mysqladmin -uusername -p shutdown

Then supply this user's password at the prompt.

Step 3: Start both servers with GTIDs enabled.  To enable GTID-based replication, each server must be started with GTID mode enabled by setting the gtid_mode variable to ON, and with the enforce_gtid_consistency variable enabled to ensure that only statements which are safe for GTID-based replication are logged. For example:

gtid_mode=ON
enforce-gtid-consistency=true

In addition, you should start slaves with the --skip-slave-start option before configuring the slave settings. For more information on GTID related options and variables, see Section 17.1.6.5, “Global Transaction ID Options and Variables”.

It is not mandatory to have binary logging enabled in order to use GTIDs when using the mysql.gtid_executed Table. Masters must always have binary logging enabled in order to be able to replicate. However, slave servers can use GTIDs but without binary logging. If you need to disable binary logging on a slave server, you can do this by specifying the --skip-log-bin and --skip-log-slave-updates options for the slave.

Step 4: Configure the slave to use GTID-based auto-positioning.  Tell the slave to use the master with GTID based transactions as the replication data source, and to use GTID-based auto-positioning rather than file-based positioning. Issue a CHANGE MASTER TO statement on the slave, including the MASTER_AUTO_POSITION option in the statement to tell the slave that the master's transactions are identified by GTIDs.

You may also need to supply appropriate values for the master's host name and port number as well as the user name and password for a replication user account which can be used by the slave to connect to the master; if these have already been set prior to Step 1 and no further changes need to be made, the corresponding options can safely be omitted from the statement shown here.

Neither the MASTER_LOG_FILE option nor the MASTER_LOG_POS option may be used with MASTER_AUTO_POSITION set equal to 1. Attempting to do so causes the CHANGE MASTER TO statement to fail with an error.

Step 5: Take a new backup.  Existing backups that were made before you enabled GTIDs can no longer be used on these servers now that you have enabled GTIDs. Take a new backup at this point, so that you are not left without a usable backup.

For instance, you can execute FLUSH LOGS on the server where you are taking backups. Then either explicitly take a backup or wait for the next iteration of any periodic backup routine you may have set up.

Step 6: Start the slave and disable read-only mode.  Start the slave like this:

The following step is only necessary if you configured a server to be read-only in Step 1. To allow the server to begin accepting updates again, issue the following statement:

GTID-based replication should now be running, and you can begin (or resume) activity on the master as before. Section 17.1.3.5, “Using GTIDs for Failover and Scaleout”, discusses creation of new slaves when using GTIDs.