synchronous replication

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Synchronous Replication MySQL Clustering

Synchronous Replication

Objective

Setup a cluster involving two MySQL servers. Connect two MySQL servers as slaves to one of the

MySQL server in the cluster, thereby making it a master. The slaves are connected using Asynchronous

replication.

Pre-requisites

1. Install the necessary Operating Systems and install MySQL server on all of them.2. All the Operating Systems should be in a network with every Operating System having its own IP

address.

Assumptions

1. The cluster is setup using MySQL servers installed on Windows Vista and Windows Server2003.

2. The MySQL Server on Windows Vista acts as a master and the slaves are installed on Fedora 10and OpenSolaris 2008.11

3. The replication process is done only for the new data so existing data will not be synchronized.Procedure

1. The primary pre-requisite for synchronous replication to be established, is that all the OperatingSystems should be connected in a network and every slave should be able to ping the master. If

there is a problem in pinging, the fire-walls at the master and slaves end should be either

disabled or properly configured to allow the slaves to communicate with master and vice-versa.


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2. Create a directory in Windows Vista to place the configuration file for the cluster. The followingsteps use the C:\mysql\mysql-cluster directory.

3. MySQL Cluster consists of four major components Management Servers, Management Clients,Data Nodes and MySQL Servers. Except Management Clients, all the others have to be declared

in a configuration file.

4. Create a file named config.ini in the C:\mysql\mysql-cluster directory. There are four mainsections

[ndbd default]

NoOfReplicas = Indicates no. of replicas in the cluster. Optimum value is 2.

[ndb_mgmd] Declare the hostname and data directory of the management server here

[ndbd] Declare the hostname and data directory of the data node here

[mysqld] Declare the hostname of the MySQL server here


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5. Open C:\Program Files\MySQL\MySQL Server 7.0\my.ini using a text editor. In the [mysqld]section, add the following two lines

ndbcluster

ndb-connectstring =

At the end of the file create three new sections and declare the connect strings and the path of

the configuration file.

[ndbd]

connect-string =

[ndb_mgm]

connect-string =

[ndb_mgmd]

config-file = C:\mysql\mysql-cluster\config.ini

In certain situations, Vista may not allow us to change the file. So copy the file somewhere,

make the change sand replace the original one.


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6. Right Click Computer, select Manage and the Services and Applications tab, move to Servicesand restart the MySQL service in Vista.

7. Start the management server using the following command in command prompt ndb_mgmd

This application is present in the bin directory of the MySQL install path. Either run this from

that directory, or include the directory in the system path.


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8. Start the data node using the following command in command prompt ndbd


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9. Start the management client using the following command in command prompt ndb_mgm


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10.Though the MySQL Server is running on the system, it is not connected to the cluster as all thedata nodes have not been started.

11.Moving to Windows 2003, open C:\Program Files\MySQL\MySQL Server 7.0\my.ini. In the[mysqld] section, add the following two lines

ndbcluster

ndb-connectstring =

At the end of the file create two new sections and declare the connect strings.

[ndbd]

connect-string =

[ndb_mgm]

connect-string =


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12.Create an empty directory with the same path as mentioned as the data directory in config.ini ofVista.

13.Restart the MySQL service in Windows 2003.


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14.Start the data node using the following command in command prompt ndbd


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15.Check the management client in Windows Vista to check if the data node has connectedproperly. Notice that the MySQL Servers now become a part of the cluster.


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16.The cluster is now setup.17.For connecting the slaves to the Windows Vista master, the procedure is similar to that of the

Asynchronous replication procedure.

18.Open C:\Program Files\MySQL\MySQL Server 5.1\my.ini using a text editor in Windows Vista(the master). In the [mysqld] section, add the following two lines

log-bin=mysql-bin

server-id=1

ndb-log-update-as-write = 1


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19.Restart the MySQL service.20.Open the MySQL console client and check the master status to make sure the master is running.


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21.Every slave should have privilege on the master to read the replication logs. Grant theappropriate privilege using the following command for each of the slave using their IP addresses

grant replication slave on *.* to user_name@IP address identified by password

22.Thats it on the masters side.23. In Fedora 10 (the slave) copy my-huge.cnf from the /usr/share/mysql directory to /etc/my.cnf.

Open it with a text editor and make the following changes -

slave-exec-mode = IDEMPOTENT

server-id=some_unique_number


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24.Either restart the mysqld process or restart the system for the effect to be seen.25.Open the MySQL console client, stop the slave, change the master and restart the slave using

the following commands in the MySQL console

stop slave;

change master to

master_host = IP_address of master,

master_user = user_name_given_in_grant,

master_password = password_given_in_grant,

master_port = default is 3306 or the port specified in the master

master_log_file = log_file_name_in_show_master_status,

master_log_pos = position of log file in show master status;

start slave;


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26.Use the following command to check the status of the slave( Both the I/O and SQL should berunning)

show slave status\G;


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27.Repeat the same procedure in the OpenSolaris 2008.11 slave.28. In the OpenSolaris 2008.11 slave, copy my-huge.cnf from the /opt/mysql/mysql/support-files

directory to any preferred directory.

29.Open it with a text editor and make the following changes -slave-exec-mode = IDEMPOTENT

server-id = some_unique_number


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30.Open the MySQL console client, stop the slave, change the master and restart the slave.


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35.One of the major drawbacks of connecting slaves asynchronously to a MySQL Cluster server isthat table creation will create inconsistency problems between the master and the slave. This is

because tables in a cluster are created using the NDB engine and on the slave the tables are

created using either the MyISAM engine or the InnoDB engine. So before the replication is

started, the required databases and tables should be setup.

36.Stop the slave; create the database and the tables.


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37.Create the databases and the tables in the MySQL cluster.


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38.Change the master properties in the slaves and restart them.


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39. Insert data at the master MySQL server using the MySQL console.

40. If the entire setup was configured properly, the same data would be available in the cluster aswell as the slaves.


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