Configuring Percona XtraDB Cluster on CentOS¶

This tutorial describes how to install and configure three Percona XtraDB Cluster nodes on CentOS 6.8 servers, using the packages from Percona repositories.

Node 1
- Host name: percona1
- IP address: 192.168.70.71
Node 2
- Host name: percona2
- IP address: 192.168.70.72
Node 3
- Host name: percona3
- IP address: 192.168.70.73

Prerequisites¶

The procedure described in this tutorial requires the following:

All three nodes have CentOS 6.8 installed.
The firewall on all nodes is configured to allow connecting to ports 3306, 4444, 4567 and 4568.
SELinux on all nodes is disabled.

Step 1. Installing PXC¶

Install Percona XtraDB Cluster on all three nodes as described in Installing Percona XtraDB Cluster on Red Hat Enterprise Linux and CentOS.

Step 2. Configuring the first node¶

Individual nodes should be configured to be able to bootstrap the cluster. For more information about bootstrapping the cluster, see Bootstrapping the First Node.

Make sure that the configuration file /etc/my.cnf on the first node (percona1) contains the following:

[mysqld]

datadir=/var/lib/mysql
user=mysql

# Path to Galera library
wsrep_provider=/usr/lib64/libgalera_smm.so

# Cluster connection URL contains the IPs of node#1, node#2 and node#3
wsrep_cluster_address=gcomm://192.168.70.71,192.168.70.72,192.168.70.73

# In order for Galera to work correctly binlog format should be ROW
binlog_format=ROW

# MyISAM storage engine has only experimental support
default_storage_engine=InnoDB

# This InnoDB autoincrement locking mode is a requirement for Galera
innodb_autoinc_lock_mode=2

# Node 1 address
wsrep_node_address=192.168.70.71

# SST method
wsrep_sst_method=xtrabackup-v2

# Cluster name
wsrep_cluster_name=my_centos_cluster

# Authentication for SST method
wsrep_sst_auth="sstuser:s3cret"

Start the first node with the following command:
```
[root@percona1 ~]# /etc/init.d/mysql bootstrap-pxc
```
Note

In case you’re running CentOS 7, the bootstrap service should be used instead:
```
[root@percona1 ~]# systemctl start mysql@bootstrap.service
```
The previous command will start the cluster with initial wsrep_cluster_address variable set to gcomm://. If the node or MySQL are restarted later, there will be no need to change the configuration file.

After the first node has been started, cluster status can be checked with the following command:

mysql> show status like 'wsrep%'

The following output shows that the cluster has been successfully bootstrapped:

+----------------------------+--------------------------------------+
| Variable_name              | Value                                |
+----------------------------+--------------------------------------+
| wsrep_local_state_uuid     | c2883338-834d-11e2-0800-03c9c68e41ec |
...
| wsrep_local_state          | 4                                    |
| wsrep_local_state_comment  | Synced                               |
...
| wsrep_cluster_size         | 1                                    |
| wsrep_cluster_status       | Primary                              |
| wsrep_connected            | ON                                   |
...
| wsrep_ready                | ON                                   |
+----------------------------+--------------------------------------+
40 rows in set (0.01 sec)

Note

It is not recommended to leave an empty password for the root account. Password can be changed as follows:

mysql@percona1> UPDATE mysql.user SET password=PASSWORD("Passw0rd") where user='root';
mysql@percona1> FLUSH PRIVILEGES;

To perform State Snapshot Transfer using XtraBackup, set up a new user with proper privileges:

mysql@percona1> CREATE USER 'sstuser'@'localhost' IDENTIFIED BY 's3cret';
mysql@percona1> GRANT PROCESS, RELOAD, LOCK TABLES, REPLICATION CLIENT ON *.* TO 'sstuser'@'localhost';
mysql@percona1> FLUSH PRIVILEGES;

Note

MySQL root account can also be used for performing SST, but it is more secure to use a different (non-root) user for this.

Step 3. Configuring the second node¶

Make sure that the configuration file /etc/my.cnf on the second node (percona2) contains the following:

[mysqld]

datadir=/var/lib/mysql
user=mysql

# Path to Galera library
wsrep_provider=/usr/lib64/libgalera_smm.so

# Cluster connection URL contains IPs of node#1, node#2 and node#3
wsrep_cluster_address=gcomm://192.168.70.71,192.168.70.72,192.168.70.73

# In order for Galera to work correctly binlog format should be ROW
binlog_format=ROW

# MyISAM storage engine has only experimental support
default_storage_engine=InnoDB

# This InnoDB autoincrement locking mode is a requirement for Galera
innodb_autoinc_lock_mode=2

# Node 2 address
wsrep_node_address=192.168.70.72

# Cluster name
wsrep_cluster_name=my_centos_cluster

# SST method
wsrep_sst_method=xtrabackup-v2

# Authentication for SST method
wsrep_sst_auth="sstuser:s3cret"

Start the second node with the following command:
```
[root@percona2 ~]# /etc/init.d/mysql start
```

After the server has been started, it should receive SST automatically. This means that the second node won’t have empty root password anymore. In order to connect to the cluster and check the status, the root password from the first node should be used. Cluster status can be checked on both nodes. The following is an example of status from the second node (percona2):

mysql> show status like 'wsrep%'

The following output shows that the new node has been successfully added to the cluster:

+----------------------------+--------------------------------------+
| Variable_name              | Value                                |
+----------------------------+--------------------------------------+
| wsrep_local_state_uuid     | c2883338-834d-11e2-0800-03c9c68e41ec |
...
| wsrep_local_state          | 4                                    |
| wsrep_local_state_comment  | Synced                               |
...
| wsrep_cluster_size         | 2                                    |
| wsrep_cluster_status       | Primary                              |
| wsrep_connected            | ON                                   |
...
| wsrep_ready                | ON                                   |
+----------------------------+--------------------------------------+
40 rows in set (0.01 sec)

Step 4. Configuring the third node¶

Make sure that the MySQL configuration file /etc/my.cnf on the third node (percona3) contains the following:

[mysqld]

datadir=/var/lib/mysql
user=mysql

# Path to Galera library
wsrep_provider=/usr/lib64/libgalera_smm.so

# Cluster connection URL contains IPs of node#1, node#2 and node#3
wsrep_cluster_address=gcomm://192.168.70.71,192.168.70.72,192.168.70.73

# In order for Galera to work correctly binlog format should be ROW
binlog_format=ROW

# MyISAM storage engine has only experimental support
default_storage_engine=InnoDB

# This InnoDB autoincrement locking mode is a requirement for Galera
innodb_autoinc_lock_mode=2

# Node #3 address
wsrep_node_address=192.168.70.73

# Cluster name
wsrep_cluster_name=my_centos_cluster

# SST method
wsrep_sst_method=xtrabackup-v2

# Authentication for SST method
wsrep_sst_auth="sstuser:s3cret"

Start the third node with the following command:
```
[root@percona3 ~]# /etc/init.d/mysql start
```

After the server has been started, it should receive SST automatically. Cluster status can be checked on all three nodes. The following is an example of status from the third node (percona3):

mysql> show status like 'wsrep%'

The following output confirms that the third node has joined the cluster:

+----------------------------+--------------------------------------+
| Variable_name              | Value                                |
+----------------------------+--------------------------------------+
| wsrep_local_state_uuid     | c2883338-834d-11e2-0800-03c9c68e41ec |
...
| wsrep_local_state          | 4                                    |
| wsrep_local_state_comment  | Synced                               |
...
| wsrep_cluster_size         | 3                                    |
| wsrep_cluster_status       | Primary                              |
| wsrep_connected            | ON                                   |
...
| wsrep_ready                | ON                                   |
+----------------------------+--------------------------------------+
40 rows in set (0.01 sec)

Testing replication¶

To test replication, lets create a new database on second node, create a table for that database on the third node, and add some records to the table on the first node.

Create a new database on the second node:
```
mysql@percona2> CREATE DATABASE percona;
```
The following output confirms that a new database has been created:
```
Query OK, 1 row affected (0.01 sec)
```
Switch to a newly created database:
```
mysql@percona3> USE percona;
```
The following output confirms that a database has been changed:
```
Database changed
```

Create a table on the third node:

mysql@percona3> CREATE TABLE example (node_id INT PRIMARY KEY, node_name VARCHAR(30));

The following output confirms that a table has been created:

Query OK, 0 rows affected (0.05 sec)

Insert records on the first node:

mysql@percona1> INSERT INTO percona.example VALUES (1, 'percona1');

The following output confirms that the records have been inserted:

Query OK, 1 row affected (0.02 sec)

Retrieve all the rows from that table on the second node:
```
mysql@percona2> SELECT * FROM percona.example;
```
The following output confirms that all the rows have been retrieved:
```
+---------+-----------+
| node_id | node_name |
+---------+-----------+
|       1 | percona1  |
+---------+-----------+
1 row in set (0.00 sec)
```
This simple procedure should ensure that all nodes in the cluster are synchronized and working as intended.