Intro to MySQL Master Slave Replication

1. Intro to MySQL Master
Slave Replication
Satej Kumar Sahu
Mindfire Solutions

2. Contents
• What is Replication?
• Concept of Master and Slave
• Advantages of Replication
• Methods of Replication
• How event based replication works?
• Demo setup of master slave replication in MySQL
• Code/config setup from the start for allowing app level support for master-slave setups later
• Scenarios best for this setup/strategy
• Conclusion
• References

3. What is Replication?
• Replication enables data from one MySQL
database server (the master) to be copied to one or
more MySQL database servers (the slaves).
• By default asynchronous.

4. Concept of Master and Slave

5. Advantages of Replication
• Scale-out solutions
• Data security
• Analytics
• Long-distance data distribution

6. Methods of Replication
• Traditional method based on replicating events
from the master's binary log, and requires the log
files and positions in them to be synchronized
between master and slave.
- Types of events: Row based (default) or statement
based or mixed type.
• Newer method based on global transaction
identifiers (GTIDs) which is transactional.

7. How event based
Replication works?

8. Demo setup of master slave
replication in MySQL
• Two AWS instances with port 3306 open for mysql
on master instance.

9. Code/config setup from the start for
allowing app level support for master-slave
setups later
• Database access layer code should have been properly abstracted/modularized
• safe_writer_connect()
safe_reader_connect()
safe_reader_statement()
safe_writer_statement()
• Important thing is to have a unified interface for connecting for reads, connecting for
writes, doing a read, and doing a write.
• May be a painful and scary process at first. The code is much easier to maintain, and
adding troubleshooting options is trivial. You need modify only one or two functions;
for example, to log how long each statement took, or which statement among those
issued gave you an error.
• Also, you can create a user for write only and read only privileges to connect to master
and slave for added separation of concern layer.

10. Scenarios best for this
setup/strategy
• Most of the cases you would not need it. A good designed, optimised, normalized
database would not require it normally.
• MySQL replication is most beneficial for a system that processes frequent reads and
infrequent or low number of writes/updates.
• Answering the following questions should help you decide whether and by how much
replication will improve the performance of your system
- read/write ratio on your system?
- How much more write load can one server handle if you reduce the reads?
- For how many slaves do you have bandwidth available on your network?
• Examples:
- Ecommerce sites
- Newspaper sites
- Online library sites
- Blogging sites
• Browsing happens much in comparison to writes.

11. Conclusion
• In most of the case, given good database design
and optimisations and use of indexes, you would
not need replication in most of the cases.
• But if you need to scale out due to large number of
reads, you should go for it :)

12. References
• http://dev.mysql.com/doc/refman/5.7/en/replication.html
• https://www.percona.com/blog/2013/01/09/how-does-
mysql-replication-really-work/
• https://dev.mysql.com/doc/refman/5.7/en/faqs-
replication.html
• https://dev.mysql.com/doc/refman/5.7/en/faqs-
replication.html#faq-replication-replication-how-benefits-
me

13. any?

14. Thank You :)