Oreilly Webcast Jan 09, 2009

MySQL Replication: Audit, Test & Verify Presented by Sean Hull, a business and technology consultant, author & speaker

MySQL Relication - How
Master records changes to binlog
Slave copies master’s binlog to relaylog via it’s IO thread
Slave replays sql from relaylog via it’s SQL thread (5.0 statement-based rep)

MySQL Replication - Limitations
Mixing transactional + non-transactional tables
Non-deterministic app code
Sysdate, current_user, load_file, uuid, user, found_rows, version
Session variables
Set max_join_size=1000
Insert into mytable values (@@max_join_size)
Locking functions - get_lock, release_lock

Audit - Application Code
dev.mysql.com/doc/refman/5.0/en/
“ Replication Features And Issues”
Look for problem functions
Look for non-transactional tables

Test - Replication Setup
Use Nagios
Look for:
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Monitor slave error log

Verify - Use Maatkit
http://code.google.com/p/maatkit/
mk-table-checksum
Checksums - compare mathematically
Checksum table
Checksum timestamps
Propogate through replication

Demo
Install Maatkit, DBI & DBD-mysql
Install MySQL Sandbox
Perform Initial Checksums
Add Bad Row & Verify
Fix Bad Row & Verify

Install Maatkit
http://www.maatkit.org/
Relevant tools:
mk-table-checksum
mk-checksum-filter
mk-slave-prefetch
mk-slave-restart
mk-slave-delay

Install MySQL Sandbox
Giuseppe Maxia
http://launchpad.net/mysql-sandbox
./make_replication_sandbox mysql-linux-5.0.67.tar.gz

Perform Initial Checksums
Connect to master
Create checksum table
Create sean_test table
Insert one row
Use mk-table-checksum on master

Add Bad Row & Verify
Add incorrect row
Verify with mk-table-checksum on slave
Redo mk-table-checksum on master
Redo mk-table-checksum on slave

Fix Bad Row & Verify
Use mk-table-sync
Use mk-table-checksum on slave
Show fix on slave
Redo mk-table-checksum on master
Redo mk-table-checksum on slave

Attendee Questions
Moving db?
datadir & innodb_data_home_dir

Attendee Questions
Transaction intensive updates
Problem of serialized writes on slave
Distribute schemas on multiple slaves
replicate_do_db
replicate_ignore_db
Prime the cache - mk-slave-prefetch
Row-based replication in 5.1
Use MyISAM storage engine on slave
Lag on slaves is normal - what are your app’s expectations?
Data archiving - do writes outside of replication
Trade safety for speed - disable binlog etc

Further Reading - Books
High Performance MySQL 2nd Ed. - Schwartz,Zaitsev, Tkachenko, Zawodny, Lentz, Balling - O’Reilly
Pro MySQL - Kruckenberg & Pipes - Apress

Further Reading - Web
http://www.xaprb.com
http://datacharmer.blogspot.com
http://planetmysql.com
http://www.mysqlperformanceblog.com

Conclusion
Reliability is not automatic
Consistency is not automatic
Replication can fail without error
Vigilance will bear fruit
Use the right tools for the job
5.1 row-based replication may mitigate some of these issues

Thank You
Sean Hull <hullsean@gmail.com>
Founder, Senior Consultant
Heavyweight Internet Group
www.iheavy.com
Ph: +1-866-268-9448
Blog: www.oracleopensource.com
www.linkedin.com/in/hullsean

Oreilly Webcast Jan 09, 2009

by Sean Hull on Feb 05, 2010

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Oreilly Webcast Jan 09, 2009 — Presentation Transcript