MySQL replication allows data to be replicated from a master database server to slave servers. It works by having the master write all data and schema changes to its binary log, which slaves then read from to apply the same changes locally. Replication can be used for backups, splitting read/write loads, and creating reporting systems on slaves. MySQL supports asynchronous replication where writes are considered complete once acknowledged locally, without waiting for confirmation from slaves. Setting up replication involves configuring replication users and server IDs, enabling binary logging on the master, restoring backups on slaves, and starting the replication process using CHANGE MASTER and START SLAVE commands. Regular monitoring is needed to check for data drift between master and slaves.

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