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 2.3.5, “Using GTIDs for Failover and Scaleout”. For information about changing GTID mode on servers online, see Section 2.5, “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:
If replication is already running, synchronize both servers by making them read-only.
Stop both servers.
Restart both servers with GTIDs enabled and the correct options configured.
The mysqld options necessary to start the servers as described are discussed in the example that follows later in this section.
Instruct the slave to use the master as the replication data source and to use auto-positioning. The SQL statements needed to accomplish this step are described in the example that follows later in this section.
Take a new backup. Binary logs containing transactions without GTIDs cannot be used on servers where GTIDs are enabled, so backups taken before this point cannot be used with your new configuration.
Start the slave, then disable read-only mode on both servers, so that they can accept updates.
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 2.2.3, “Creating a User for Replication” for information about
adding a specific user for replication connections and
Section 2.2.1, “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
Using Option Files for more information. Alternatively
you can use startup options when running
Most of the steps that follow require the use of the MySQL
root account or another MySQL user account that
SUPER privilege or the
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:
mysql> SET @@GLOBAL.read_only = ON;
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.
It is important to understand that logs containing transactions without GTIDs cannot be used on servers where GTIDs are enabled. Before proceeding, you must be sure that transactions without GTIDs do not exist anywhere in the topology.
Step 2: Stop both servers.
Stop each server using mysqladmin as shown
username is the user name
for a MySQL user having sufficient privileges to shut down the
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
variable enabled to ensure that only statements which are safe
for GTID-based replication are logged. For example:
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 2.6.5, “Global Transaction ID System 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
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
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.
mysql> CHANGE MASTER TO > MASTER_HOST = host, > MASTER_PORT = port, > MASTER_USER = user, > MASTER_PASSWORD = password, > MASTER_AUTO_POSITION = 1;
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
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
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:
mysql> START SLAVE;
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:
mysql> SET @@GLOBAL.read_only = OFF;
GTID-based replication should now be running, and you can begin (or resume) activity on the master as before. Section 2.3.5, “Using GTIDs for Failover and Scaleout”, discusses creation of new slaves when using GTIDs.