Configuring MySQL Master-Master Replication

Updated by James Stewart

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MySQL Master-Master replication adds speed and redundancy for active websites. With replication, two separate MySQL servers act as a cluster. Database clustering is particularly useful for high availability website configurations. Use two separate Linodes to configure database replication, each with private IPv4 addresses.

This guide is written for a non-root user. Commands that require elevated privileges are prefixed with sudo. If you’re not familiar with the sudo command, you can check our Users and Groups guide.

This guide is written for Debian 7 or Ubuntu 14.04.

Install MySQL

Use the following commands to install MySQL on each of the Linodes:

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sudo apt-get update
sudo apt-get upgrade -y
sudo apt-get install mysql-server mysql-client

Edit MySQL’s Configuration

  1. Edit the /etc/mysql/my.cnf file on each of the Linodes. Add or modify the following values:

    Server 1:

    /etc/mysql/my.cnf
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    server_id           = 1
    log_bin             = /var/log/mysql/mysql-bin.log
    log_bin_index       = /var/log/mysql/mysql-bin.log.index
    relay_log           = /var/log/mysql/mysql-relay-bin
    relay_log_index     = /var/log/mysql/mysql-relay-bin.index
    expire_logs_days    = 10
    max_binlog_size     = 100M
    log_slave_updates   = 1
    auto-increment-increment = 2
    auto-increment-offset = 1
    

    Server 2:

    /etc/mysql/my.cnf
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    server_id           = 2
    log_bin             = /var/log/mysql/mysql-bin.log
    log_bin_index       = /var/log/mysql/mysql-bin.log.index
    relay_log           = /var/log/mysql/mysql-relay-bin
    relay_log_index     = /var/log/mysql/mysql-relay-bin.index
    expire_logs_days    = 10
    max_binlog_size     = 100M
    log_slave_updates   = 1
    auto-increment-increment = 2
    auto-increment-offset = 2
    
  2. For each of the Linodes, edit the bind-address configuration in order to use the private IP addresses:

    /etc/mysql/my.cnf
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    bind-address    = x.x.x.x
    
  3. Once completed, restart the MySQL application:

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    sudo service mysql restart
    

Create Replication Users

  1. Log in to MySQL on each of the Linodes:

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    mysql -u root -p
    
  2. Configure the replication users on each Linode. Replace x.x.x.x with the private IP address of the opposing Linode, and password with a strong password:

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    GRANT REPLICATION SLAVE ON *.* TO 'replication'@'x.x.x.x' IDENTIFIED BY 'password';
    
  3. Run the following command to test the configuration. Use the private IP address of the opposing Linode:

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    mysql -ureplication -p -h x.x.x.x -P 3306
    

    This command should connect you to the remote server’s MySQL instance.

Configure Database Replication

  1. While logged into MySQL on Server 1, query the master status:

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    SHOW MASTER STATUS;
    

    Note the file and position values that are displayed:

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    mysql> SHOW MASTER STATUS;
    +------------------+----------+--------------+------------------+
    | File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
    +------------------+----------+--------------+------------------+
    | mysql-bin.000001 |      277 |              |                  |
    +------------------+----------+--------------+------------------+
    1 row in set (0.00 sec)
    
  2. On Server 2 at the MySQL prompt, set up the slave functionality for that database. Replacex.x.x.x with the private IP from the first server. Also replace the value for master_log_file with the file value from the previous step, and the value for master_log_pos with the position value.

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    SLAVE STOP;
    CHANGE MASTER TO master_host='x.x.x.x', master_port=3306, master_user='replication', master_password='password', master_log_file='mysql-bin.000001', master_log_pos=106;
    SLAVE START;
    
  3. On Server 2, query the master status. Again note the file and position values.

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    SHOW MASTER STATUS;
    
  4. Set the slave database status on Server 1, replacing the same values swapped in step 2 with those from the Server 2.

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    SLAVE STOP;
    CHANGE MASTER TO master_host='x.x.x.x', master_port=3306, master_user='replication', master_password='password', master_log_file='mysql-bin.000001', master_log_pos=277;
    SLAVE START;
    
  5. Test by creating a database and inserting a row:

    Server 1:

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    create database test;
    create table test.flowers (`id` varchar(10));
    

    Server 2:

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    show tables in test;
    

When queried, you should see the tables from Server 1 replicated on Server 2. Congratulations, you now have a MySQL Master-Master cluster!

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

This guide is published under a CC BY-ND 4.0 license.