Deploy a Replica Server with MariaDB Community Server 10.5¶

Configuration Files¶

MariaDB's packages include several bundled configuration files. It is also possible to create custom configuration files.

On RHEL, CentOS, and SLES, MariaDB's packages bundle the following configuration files:

• /etc/my.cnf

• /etc/my.cnf.d/client.cnf

• /etc/my.cnf.d/mysql-clients.cnf

• /etc/my.cnf.d/server.cnf

And on RHEL, CentOS, and SLES, custom configuration files from the following directories are read by default:

• /etc/my.cnf.d/

On Debian and Ubuntu, MariaDB's packages bundle the following configuration files:

• /etc/mysql/my.cnf

• /etc/mysql/mariadb.cnf

• /etc/mysql/mariadb.conf.d/50-client.cnf

• /etc/mysql/mariadb.conf.d/50-mysql-clients.cnf

• /etc/mysql/mariadb.conf.d/50-mysqld_safe.cnf

• /etc/mysql/mariadb.conf.d/50-server.cnf

• /etc/mysql/mariadb.conf.d/60-galera.cnf

And on Debian and Ubuntu, custom configuration files from the following directories are read by default:

• /etc/mysql/conf.d/

• /etc/mysql/mariadb.conf.d/

Configuring MariaDB¶

1. Determine which system variables and options you need to configure.

   Mandatory system variables and options for a Replica Server include:

   System Variable/Option	Description
   server_id	Sets the numeric Server ID for this MariaDB Community Server. Must be unique in the deployment.

   Useful system variables and options for MariaDB Community Server include:

   System Variable/Option	Description
   datadir	Sets the path to the data directory. MariaDB Community Server writes data files to this directory, including tablespaces, logs, and schemas. Change it to use a non-standard location or to start the Server on a different data directory for testing.
   bind_address	Sets the local TCP/IP address on which MariaDB Community Server listens for incoming connections. Bind to 0.0.0.0 to make the Server accessible through any network interface.
   port	Sets the port MariaDB Community Server listens on. Use this system variable to use a non-standard port or when running multiple Servers on the same host for testing.
   max_connections	Sets the maximum number of simultaneous connections MariaDB Community Server allows.
   thread_handling	Sets how MariaDB Community Server handles threads for client connections.
   log_error	Sets the file name for the error log.
   innodb_buffer_pool_size	Sets the amount of memory InnoDB reserves for the Buffer Pool.
   innodb_log_file_size	Sets the size for each Redo Log file and innodb_log_files_in_group sets the number of Redo Log files used by InnoDB.
   innodb_io_capacity	Sets the maximum number of I/O operations per second that InnoDB can use.

   Useful system variables and options for a Replica Server include:

   System Variable/Option	Description
   log_bin	Set this option to enable the Binary Log, allowing the Replica Server to replace the Primary Server if it goes down.
   relay_log	Sets the location for the Relay Log.
   log_slave_updates	Sets the Replica Server to log updates from the slave thread to the Binary Log. Use this if you want to daisy chain Replica Servers.
   gtid_domain_id	Sets the numeric domain identifier to use in Global Transaction ID's.
   gtid_ignore_duplicates	Set when using multi-source replication to ignore Binary Log events with duplicate Global Transaction ID's.
   gtid_strict_mode	Set to ensure that GTIDs are monotonically increasing..
   report_host	Sets the IP address or hostname the Replica Server sends to the Primary Server during its registration.
   report_port	Sets the port number the Replica Server sends to the Primary Server during its registration.

2. Choose a configuration file in which to configure your system variables and options.

   It not recommended to make custom changes to one of the bundled configuration files. Instead, it is recommended to create a custom configuration file in one of the included directories. Configuration files in included directories are read in alphabetical order. If you want your custom configuration file to override the bundled configuration files, then it is a good idea to prefix the custom configuration file's name with a string that will be sorted last, such as z-.

   • On RHEL, CentOS, and SLES, a good custom configuration file would be: /etc/my.cnf.d/z-custom-my.cnf

   • On Debian and Ubuntu, a good custom configuration file would be: /etc/mysql/mariadb.conf.d/z-custom-my.cnf

3. Set your system variables and options in the configuration file.

   They need to be set in a group that will be read by mariadbd, such as [mariadb] or [server].

   For example:

   [mariadb]
   
   # Server Configuration
   log_error                 = mariadbd.err
   innodb_buffer_pool_size   = 1G
   
   # Replication Configuration (Replica Server)
   log_bin                = mariadb-bin
   server_id              = 2
   log_slave_updates      = ON
   binlog_format          = ROW
   

Parallel Replication¶

Writes to the Primary Server that are group committed or logged with a Global Transaction ID in different replication domains can be applied on the Replica Server using parallel threads to improve performance.

Semi-Synchronous Replication¶

MariaDB Replication deployments that use MariaDB Community Server 10.2 have the option of enabling semi-synchronous replication for Replica Servers through the semisync_slave plugin.

Mandatory additional options and system variables for Semi-Synchronous Replication:

Backing Up the Primary Server¶

Before the Replica Server can be started, its data needs to be consistent with the Primary Server. To ensure that it is consistent, take a backup of the Primary Server:

The instructions below show how to perform a backup using MariaDB Backup. For more information about backing up and restoring the database, please see the Recovery Guide.

1. On the Primary Server, take a full backup.

   On MariaDB Community Server 10.4 and later:

   $ sudo mariadb-backup --backup \
         --user=mariabackup_user \
         --password=mariabackup_passwd \
         --target-dir=/data/backup/replica_backup
   

   On MariaDB Community Server 10.3 and earlier:

   $ sudo mariabackup --backup \
         --user=mariabackup_user \
         --password=mariabackup_passwd \
         --target-dir=/data/backup/replica_backup
   

   Confirm successful completion of the backup operation.

2. On the Primary Server, prepare the backup.

   On MariaDB Community Server 10.4 and later:

   $ sudo mariadb-backup --prepare \
         --target-dir=/data/backup/replica_backup
   

   On MariaDB Community Server 10.3 and earlier:

   $ sudo mariabackup --prepare \
         --target-dir=/data/backup/replica_backup
   

   Confirm successful completion of the prepare operation.

Restoring the Backup on the Replica Server¶

To make the Replica Server consistent with the Primary Server, we restore the new backup on the Replica:

1. On the Primary Server, copy the backup to the Replica Server:

   $ sudo rsync -av /data/backup/replica_backup replicaserver:/data/backup/
   

2. On the Replica Server, restore the backup using MariaDB Backup.

   On MariaDB Community Server 10.4 and later:

   $ sudo mariadb-backup --copy-back \
      --target-dir=/data/backup/replica_backup
   

   On MariaDB Community Server 10.3 and earlier:

   $ sudo mariabackup --copy-back
      --target-dir=/data/backup/replica_backup
   

3. On the Replica Server, fix the file permissions of the restored backup:

   $ sudo chown -R mysql:mysql /var/lib/mysql
   

4. After the backup has been restored on the Replica Server, we can start MariaDB Community Server, and confirm that the backup is valid by ensuring that the server starts properly and that all data was properly imported.

Starting the Server¶

MariaDB Community Server includes configuration to start, stop, restart, enable/disable on boot, and check the status of the Server using the operating system default process management system.

For distributions that use systemd (most supported OSes), you can manage the Server process using the systemctl command:

For distributions that use Upstart (RHEL6, CentOS 6), you can manage the Server process using the service and chkconfig utilities:

Starting MariaDB Replication¶

The last step is to set up MariaDB Replication.

1. Get the GTID position that corresponds to the restored backup.

   If the backup was taken with MariaDB Backup, this position will be located in xtrabackup_binlog_info:

   $ cat xtrabackup_binlog_info
   mariadb-bin.000096 568 0-1-2001,1-2-5139
   

   The GTID position from the above output is 0-1-2001,1-2-5139.

2. Connect to the Replica Server using MariaDB Client using the root@localhost user account:

   $ sudo mariadb
   

3. Set the gtid_slave_pos system variable to the GTID position:

   SET GLOBAL gtid_slave_pos='0-1-2001,1-2-5139';
   

4. Execute the CHANGE MASTER TO statement to configure the Replica Server to connect to the Primary Server at this position:

   CHANGE MASTER TO
      MASTER_USER = "repl",
      MASTER_HOST = "192.0.2.1",
      MASTER_PASSWORD = "repl_passwd",
      MASTER_USE_GTID=slave_pos;
   

   The above statement configures the Replica Server to connect to a Primary Server located at 192.0.2.1 using the repl user account. These account credentials must first be configured on the primary server.

5. Start replication using the START SLAVE command:

   START SLAVE;
   

   The above statement configures the Replica Server to connects to the Primary Server to retrieve new binary log events and replicate them into the local database.

Checking Replication Status¶

1. Connect to the Replica Server using MariaDB Client using the root@localhost user account:

   $ sudo mariadb
   Welcome to the MariaDB monitor.  Commands end with ; or \g.
   Your MariaDB connection id is 38
   Server version: 10.5.4-MariaDB MariaDB Server
   
   Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
   
   Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
   
   MariaDB [(none)]>
   

2. Execute the SHOW SLAVE STATUS statement.

   This statement returns a lot of columns, but the important ones are Slave_IO_Running and Slave_SQL_Running. If both of those say Yes, then replication is running correctly.

   SHOW SLAVE STATUS\G
   
   *************************** 1. row ***************************
                   Slave_IO_State: Waiting for master to send event
                      Master_Host: 178.128.150.186
                      Master_User: repl
                      Master_Port: 3306
                    Connect_Retry: 60
                  Master_Log_File: mariadb-bin.000003
              Read_Master_Log_Pos: 4919
                   Relay_Log_File: mysqld-relay-bin.000003
                    Relay_Log_Pos: 3913
            Relay_Master_Log_File: mariadb-bin.000003
                 Slave_IO_Running: Yes
                Slave_SQL_Running: Yes
                  Replicate_Do_DB:
              Replicate_Ignore_DB:
               Replicate_Do_Table:
           Replicate_Ignore_Table:
          Replicate_Wild_Do_Table:
      Replicate_Wild_Ignore_Table:
                       Last_Errno: 0
                       Last_Error:
                     Skip_Counter: 0
              Exec_Master_Log_Pos: 4919
                  Relay_Log_Space: 5138
                  Until_Condition: None
                   Until_Log_File:
                    Until_Log_Pos: 0
               Master_SSL_Allowed: No
               Master_SSL_CA_File:
               Master_SSL_CA_Path:
                  Master_SSL_Cert:
                Master_SSL_Cipher:
                   Master_SSL_Key:
            Seconds_Behind_Master: 0
    Master_SSL_Verify_Server_Cert: No
                    Last_IO_Errno: 0
                    Last_IO_Error:
                   Last_SQL_Errno: 0
                   Last_SQL_Error:
      Replicate_Ignore_Server_Ids:
                 Master_Server_Id: 1
                   Master_SSL_Crl:
               Master_SSL_Crlpath:
                       Using_Gtid: No
                      Gtid_IO_Pos:
          Replicate_Do_Domain_Ids:
      Replicate_Ignore_Domain_Ids:
                    Parallel_Mode: conservative
                        SQL_Delay: 0
              SQL_Remaining_Delay: NULL
          Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
                 Slave_DDL_Groups: 17
   Slave_Non_Transactional_Groups: 0
       Slave_Transactional_Groups: 7
   

Testing Replication¶

1. Connect to the Primary Server using MariaDB Client using the root@localhost user account:

   user@primary-server$ sudo mariadb
   

2. Create a database with the CREATE DATABASE statement:

   CREATE DATABASE IF NOT EXISTS test;
   

3. Create a table with the CREATE TABLE statement:

   CREATE TABLE test.names (
      id INT PRIMARY KEY AUTO_INCREMENT,
      name VARCHAR(255));
   

4. Insert some data with the INSERT statement:

   INSERT INTO test.names(name) VALUES
      ("Walker Percy"), ("Kate Chopin"), ("William Faulkner"), ("Jane Austen");
   

5. Confirm that the data was inserted properly with the SELECT statement:

   SELECT * FROM test.names;
   
   +----+------------------+
   | id | name             |
   +----+------------------+
   |  1 | Walker Percy     |
   |  2 | Kate Chopin      |
   |  3 | William Faulkner |
   |  4 | Jane Austen      |
   +----+------------------+
   

6. Connect to the Replica Server and start MariaDB Client:

   user@cluster-node2$ sudo mariadb
   

7. Confirm that the data was replicated properly with the SELECT statement:

   SELECT * FROM test.names;
   
   +----+------------------+
   | id | name             |
   +----+------------------+
   |  1 | Walker Percy     |
   |  2 | Kate Chopin      |
   |  3 | William Faulkner |
   |  4 | Jane Austen      |
   +----+------------------+
   

   We can confirm that the DDL and DML were replicated from the other Replica Server, allowing both Servers to return the same data.

Next steps:

• Deploy MaxScale with MariaDB Monitor and Read/Write Split Router

• Deploy MaxScale with MariaDB Monitor and Read Connection Router