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Mastering Galera

Mastering Galera. Data Masters. Special Thanks To…. 1010 NE 2 nd Ave Miami, FL 33132 305-735-1274 www.venturehive.co. Our Sponsor!. John Jadvani 954-527-0090. Short bio about me… Andrew Simkovsky 15 years working with database technology

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Mastering Galera

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  1. MasteringGalera Data Masters

  2. Special Thanks To… 1010 NE 2nd Ave Miami, FL 33132 305-735-1274 www.venturehive.co

  3. Our Sponsor! John Jadvani 954-527-0090

  4. Short bio about me… • Andrew Simkovsky • 15 years working with database technology • Oracle, MySQL/MariaDB, SQL Server, Postgres • Redis, MongoDB, CouchDB, Cassandra, Neo4j • Worked across many industries • Consulting, Retail, Telecommunications, Energy • Data, Marketing, Gaming, Health care

  5. DBTekPro www.dbtekpro.com andrew@dbtekpro.com @asimkovsky

  6. Let’s Get Started!

  7. Galera Cluster for MySQL • High availability (HA) and scaling solution for MySQL/MariaDB • A clustering solution that integrates with MySQL / MariaDB

  8. Galera Cluster Concept MySQL/MariaDB Galera

  9. Other HA and Scaling Solutions • Sharding • Master / Slave(s) • Master / Master • Master / Master plus Slaves

  10. Sharding Application A..F G..L M..R …

  11. Master / Slave(s) Application Master Slave

  12. Master / Slave(s) Application Master Slave Slave Slave

  13. Master / Master Application Master Master

  14. Master / Master Plus Slaves Application Master Master Slave Slave Slave Slave Slave Slave

  15. Basic Galera Concepts • Contains multiple nodes • Each node has a full copy of the data • Synchronous multi-master replication across all nodes • All changes to every node are replicated to all other nodes • Each node can be for reads and writes • All nodes can be accessed at the same time

  16. Galera Concept Application Node Node Node Node Node Galera Galera Galera Galera Galera

  17. Quorum Commit • Don’t have to wait for all nodes to answer back for your changes • “Majority” rules • Committed nodes >= (N / 2 ) + 1 • Minimum recommended number of nodes is 3

  18. Split Brain Syndrome • Network partition between the nodes • Each node thinks its in charge • Both nodes keep taking traffic • Now both nodes have different contents • When nodes start talking to each other again, they are very confused

  19. Split Brain Syndrome Data Center 1 Data Center 2 Application Application Node Node Galera Galera

  20. Arbitrator Node • “Cheating” with 2 nodes • Acts as a third node • Doesn’t store any data • Aware of cluster state and replication status • Provides that third “commit” vote • Replication changes pass through it • Loss of direct connectivity between nodes can still be handled if arbitrator can talk to both

  21. Arbitrator Node Data Center 1 Data Center 2 Application Application Node Node Galera Galera Arbitrator Data Center 3

  22. Some Other “Gotchas” • Be careful with non-deterministic functions like NOW(), CURTIME(), etc • DELETE commands on tables without a primary key are not supported • Direct writes to system tables (“mysql” database) are not replicated • Cluster enforces optimistic concurrency control • “I got here first, my transaction is good” • All other transactions locking the same row get deadlock error • Application should be configured to retry the transaction

  23. Setup Overview

  24. Stuff to install on each node • Operating system • MariaDB server • Galera • PerconaXtraBackup

  25. Setup Steps • On each node: • Set up configuration files • Start up MySQL • On first node: during startup, you tell it that it’s the first node. • The data it contains will become the “master” copy. • For each additional node that starts up, it will seek out one of its “neighbors”, and try to sync a copy of the data to itself • Source node is called the “donor” • After syncing the data, the node joins the cluster and becomes active

  26. Database State Transfer • When starting up, each node needs a copy of the data • The copying of the data is called a “state transfer” • Will copy from existing nodes using one of these methods: • mysqldump • rsync • xtrabackup • For mysqldump and rsync, the donor is locked for writes during the entire copy process • Percona’sxtrabackup allows writes to happen on donor node during copy process

  27. Live Demo!

  28. Questions?

  29. Thank You For Coming! Please rate this Meet Up: www.meetup.com/data-masters (or go there to join!) Check out my blog and forums: www.dbtekpro.com

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