1. MySQL Replication
19 April 2014
Abdul Manaf

2. Agenda
• Basics of Replication
• Why Replication needed
• Types Of Replication
• Replication For MySQL
• Configuring MySQL Replication
• Test a Replicated MySQL System

3. Basics of Replication
• Master / Slave, Master / Master and Circular replication
• Master writes all DDL and DML statements in the binary log
• Slaves read the binary log from the master and run the queries
locally
• A master can have many slaves
• A slave can have only one master
• A server can be both a master and a slave
• MySQL Replication is asynchronous

4. Master - Slave and Master-Master Replication Architecture
Master – Slave
Master – Master

5. Circular Replication Architecture

6. Why Replication needed
• Using Replication for Backups : Data is replicated to the slave, and
the slave can pause the replication process, it is possible to run backup
services on the slave without touching the corresponding master data.
• Using Replication with Different Master and Slave Storage Engines for
performance
• Using Replication for Scale-Out i.e Splitting load between servers
Distributing READ and WRITE.
• Creating reporting system on slave

7. Types Of Replication
• Synchronous Replication
• Asynchronous Replication

8. Synchronous Replication
• Master Server waits for the data to have been recorded on the duplicated
systems.
• Write either completes on both sides or not at all
• Uses the two-phase commit technology to protect data integrity
• Synchronous replication is essential for failover of transactional applications.
With synchronous replication, all committed data on the disk of the first server
are on the disk of the second server.
• Not in MySQL

9. Asynchronous Replication
• Write is considered complete as soon as local storage acknowledges.
• Performance is greatly increased. No need for two-phase commit protocol.
• In case of losing a local storage, the remote storage is not guaranteed to
have the current copy of data.
• Slaves need not be connected permanently to receive updates from the
master

10. Considerations before setting replication
• MySQL version of servers should be same.
• Master and slave should be able to commuincate with each other, create a test use
on master and try to connect from slave.

11. How to set MySQL replication
• Configure replication account on the master i.e create a mysql replication
user.
• Enable binary log and set server-id on the master my.cnf file
• Restart mysql master server
• Take backup from master server
• Configure slave for replication
• Restore backup on slave server
• Start replication using CHANGE MASTER and START SLAVE

12. Configure my.cnf
• Enable binary logging on the master
• Setup a server-id for the master
• Ensure that the skip-networking option has not been enabled, so that slave
can communicate with it

13. Configure my.cnf

14. Configure my.cnf

15. Configure slave server
• Setup a server-id on slave as we have done on master, it should be
different from master.
• Other variables like for configuring slave MASTER_HOST ,
MASTER_USER , MASTER_PASSWORD etc. We will be setting them by
executing CHNAGE master
CHANGE MASTER TO
MASTER_HOST = '192.168.9.236'
MASTER_USER = 'repl'
MASTER_PASSWORD = 'repl@123'
MASTER_LOG_FILE = 'mysql-bin.000004'
MASTER_LOG_POS = 108;

16. Known issues and their resolutions
• MySQL replication can fail silently, that is data can drift out of sync with the
master without your knowing, You need to regularly monitor your replication
setups.
• Use checksum tools from Percona to verify & compare tables on master &
slave servers.
• Use rigorous monitoring to watch error logs, and checksum logs hourly if
necessary.
• Use Percona sync tools to resync tables if they get out of sync.
• Be especially vigilant if you’re taking backups off the slave server

17. THANK YOU ALL