Template:OXLoadBalancingClustering Database

Master/Master database setup

This article describes the setup process "Master/Master replication" for new database nodes. During configuration and initialization, other database operations must be prohibited.

The Master/Master replication is a vice versa setup of Master/Slave configurations. This Means each server is afterwards the slave of the other.

Server IPs in the example are 1.1.1.1 and 9.9.9.9

Startup both database machines and install the mysql server packages

$ apt-get install mysql-server

During the installation, a dialog will show up to set a password for the MySQL 'root' user.

Open the MySQL configuration file on both servers:

$ vim /etc/mysql/my.cnf

Modify or enable the following configuration options in the mysqld-section, use 1 as ${unique Number} on the server 1.1.1.1 and 2 for 2.2.2.2:

bind-address            = 0.0.0.0
server-id              = ${unique Number}
log-bin                 = /var/log/mysql/mysql-bin.log

• bindaddress specifies the network address where MySQL is listening for network connections. Since the MySQL slave and both Open-Xchange Servers are dedicated machines it is required to have the master accessible through the network.
• server-id is just a unique number within a environment with multiple MySQL servers. It needs to be unique for each server in a replication cluster.
• log-bin enables the MySQL binary log which is required for Master/Master replication. In general every statement triggered at the database is stored there to get distributed through the database cluster.

To apply the configuration changes, restart the MySQL servers.

$ /etc/init.d/mysql restart

Then login to MySQL with the credentials given at the MySQL installation process

$ mysql -u root -p
Enter password:

First Master configuration

Choose one server to start with as the first Master (here we use 1.1.1.1).

Create a MySQL user with rights "REPLICATION". This account is used by the MySQL slave to fetch database updates. In this example, the username is "replication":

 mysql> GRANT REPLICATION SLAVE ON *.* TO 'replication'@'9.9.9.9' IDENTIFIED BY 'secret';

Verify that the MySQL daemon writes a binary log and remember the log Position:

mysql> SHOW MASTER STATUS;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000001 |      1111 |              |                  |
+------------------+----------+--------------+------------------+

Copy the MySQL binary logs and the index file to the slave. This is required for the initial synchronization.

$ scp /var/log/mysql/mysql-bin.* root@9.9.9.9:/var/log/mysql

First Slave configuration

On 9.9.9.9, set the MySQL system user as owner of the binary log that has just been copied to the slave.

$ chown mysql:adm /var/log/mysql/*

Configure 1.1.1.1 as Master Server. Use the remembered log file position from 1.1.1.1.

mysql> CHANGE MASTER TO MASTER_HOST='1.1.1.1', MASTER_USER='replication', MASTER_PASSWORD='secret', MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=1111;

Start the MySQL slave replication

mysql> START SLAVE;

An check the status

mysql> SHOW SLAVE STATUS;

"Slave_IO_Running" and "Slave_SQL_Running" should be set to "yes".

Second Master configuration

This means, the first Master/Slave Replication is working and the "reverse" replication needs to be prepared. Please now create the replication user on 9.9.9.9:

 mysql> GRANT REPLICATION SLAVE ON *.* TO 'replication'@'1.1.1.1' IDENTIFIED BY 'secret';

Verify that the MySQL daemon writes a binary log and remember the log Position:

mysql> SHOW MASTER STATUS;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000001 |      1111|              |                  |
+------------------+----------+--------------+------------------+

Second Slave configuration

1.1.1.1 is now the slave in this context and 9.9.9.9 one is the master. Log in to 1.1.1.1

Configure 9.9.9.9 as Master Server. Use the remembered log file position from the master (1.1.1.1).

mysql> CHANGE MASTER TO MASTER_HOST='9.9.9.9', MASTER_USER='replication', MASTER_PASSWORD='secret', MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=xxx;

start the MySQL slave replication

mysql> START SLAVE;

and check the status

mysql> SHOW SLAVE STATUS;

"Slave_IO_Running" and "Slave_SQL_Running" should be set to "yes".

Also check the syslog if the replication has been sucessfully started

$ tail -fn20 /var/log/syslog
Jul 26 19:03:45 dbslave mysqld[4718]: 090726 19:03:45 [Note] Slave I/O thread: connected to master 'replication@10.20.30.217:3306',  replication started in log 'mysql-bin.000001' at position 1082

Testing Master/Master

On the first master, create a new database in MySQL:

mysql> CREATE DATABASE foo;

Check if this database is available on the second master:

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| foo                |
| mysql              |
+--------------------+

Delete the database on the second master:

mysql> DROP DATABASE foo;

Check if the database has been removed at first master

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
+--------------------+

Creating Open-Xchange user

Now setup access for the Open-Xchange Server database user 'openexchange' to configdb and the oxdb for both groupware server addresses. These databases do not exist yet, but will be created during the Open-Xchange Server installation.

mysql> GRANT ALL PRIVILEGES ON *.* TO 'openexchange'@'10.20.30.213' IDENTIFIED BY 'secret';
mysql> GRANT ALL PRIVILEGES ON *.* TO 'openexchange'@'10.20.30.215' IDENTIFIED BY 'secret';