This document discusses online migration from an existing MySQL master-slave setup to a Galera cluster. It outlines the steps to enable binary logging on the slave, dump the schema and data, load this into the first Galera node to initialize replication, and transition reads to the Galera cluster while writes continue on the master initially at 90% before being cut over fully to the cluster. Operational checklists, backup procedures, and disaster recovery options for the new Galera cluster configuration are also reviewed.

1. Migrating to MySQL, MariaDB
Galera, and/or Percona XtraDB
Cluster
March 2014
Johan Andersson
Severalnines AB
johan@severalnines.com
Mobile +46 73 073 60 99

2. Online Migration
! Existing MySQL Server
! E.g Master – Slave setup
! Single server
! Tired of slave lag and data loss?
! Easy scaling w/o read/write splits?
! Feasibility - Data set, queries, suits Galera
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3. Online Migration
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Master – Slave
RW R
Galera Cluster
m1 s1 gm1 gm2 gm3
Setup with
http://www.severalnines.com/galera-configurator
Existing setup
(examples based on 5.5)

4. Online Migration
! On s1:
! Enable
log-bin=binlog
log-slave-updates=1
! GRANT
REPLICATION_SLAVE ON
*.* TO ‘repl’@’gm1’
IDENTIFIED BY ‘repl’
! Dump schema and data
into two separate files.
! Easier to convert the
schema
! Best: convert schema
already on slave
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Master – Slave
RW R
m1 s1

5. Online Migration
! On gm1:
! Load in converted schema
! Load in data
! CHANGE MASTER TO
MASTER_HOST=‘s1’,
MASTER_USER=‘repl’,
MASTER_PASSWORD=‘repl’;
! START SLAVE;
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Galera Cluster
gm1 gm2 gm3

6. Online Migration
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Master – Slave Galera Cluster
RW R
R/W

7. Online Migration
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Master – Slave Galera Cluster
RW R
90% R/W 10% Reads

8. Cut Off
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Master – Slave Galera Cluster
RW R
R/W

9. Demo Time!
! Setting up Replication from Master to Galera Cluster
(acting as a slave cluster).
! Master – Percona Server 5.5
! Slave - 3 Node Galera Cluster – PXC 5.6
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Master Galera Cluster

10. Operational Checklist
! Are queues building up?
! Slow queries? Tune queries in the Query Monitor.
! Are backups working?
! Reporting queries?
! Latency issue?
! Do you have random node restarts and failures? Time to upgrade.
! Did you test new code before putting in production?
You worst enemy is the network administrator!
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11. Belt and Suspenders
! Apply your backup procedures as normal
! mysqldump –single-transaction
! s9s_backup, front-end to xtrabackup
http://johanandersson.blogspot.se/2012/10/hotbackup-of-galera-cluster-for-
mysql.html
! http://www.severalnines.com/blog/full-restore-mysql-galera-cluster-backup
! You may still want to have an async slave connected to the cluster
! Reporting
! Disaster Recovery
! http://www.severalnines.com/blog/asynchronous-replication-galera-cluster-
mysql-server-gtid’
! Point in time recovery
! http://www.severalnines.com/blog/point-time-recovery-galera-cluster
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12. Q & A
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13. Thank you.
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For further questions please contact John-Jerome Schmidt:
jj@severalnines.com