Lessons from database failures



1.Lessons from database failures Colin Charles, Chief Evangelist, Percona Inc. colin.charles@percona.com / byte@bytebot.net http://www.bytebot.net/blog/ | @bytebot on Twitter Percona Webminar 18 January 2017

2.whoami • Chief Evangelist (in the CTO office), Percona Inc • Focusing on the MySQL ecosystem (MySQL, Percona Server, MariaDB Server), as well as the MongoDB ecosystem (Percona Server for MongoDB) + 100% open source tools from Percona like Percona Monitoring & Management, Percona xtrabackup, Percona Toolkit, etc. • Founding team of MariaDB Server (2009-2016), previously at Monty Program Ab, merged with SkySQL Ab, now MariaDB Corporation • Formerly MySQL AB (exit: Sun Microsystems) • Past lives include Fedora Project (FESCO), OpenOffice.org • MySQL Community Contributor of the Year Award winner 2014

3.Agenda • Backups (and verification) • Replication (and failover) • Security (and encryption)


5.ma.gnolia.com’s failure • January 30 2009: complete outage • February 17 2009: data corruption in the UDB, essentially dead • What happened? • Ruby on Rails on four self-hosted Mac Mini’s, a couple of XServe’s, 500GB+ MySQL 5 DB • Filesystem corruption, corrupted database backup • No versioning, didn’t check if the backups worked, made use of rsync to backup the database over Firewire network

6.ma.gnolia.com today? • EC2 for the app with EBS snapshots, RDS with snapshots, Multi-AZ deployment • Self-hosted? • xtrabackup • START TRANSACTION WITH CONSISTENT SNAPSHOT + mysqldump —single-transaction —master-data • Backup a replica • Replication event checksums

7.Couchsurfing, 2006

8.Couchsurfing problems 1. major, avoidable hard drive crash 2. incremental backups weren’t executed in the correct manner, and twelve of our most important data files didn’t survive

9.Time-delayed replication • MySQL 5.6+ has time-delayed replication. Stop replication when you know a mistake has happened before it propagates to all the slaves. • Feature suggestion since 2001! Bug reported August 2006 (mysql#21639). Pushed June 2010 (WL#344). GA February 2013.

10.Why replicate? • Scale out • [automatic] (master) failover • Geographical redundancy across multiple data centres • Online schema changes

11.Replication • Asynchronous (default) • (Enhanced loss-less) Semi-synchronous (plugin) • Synchronous (Galera, group replication, NDBCLUSTER) • DRBD

12.Frameworks • MySQL-MMM • Percona Replication Manager • Severalnines ClusterControl (https://github.com/percona/ percona-pacemaker-agents/) • Orchestrator • Replication Manager • MySQL MHA (github.com/tanji/replication- • Tungsten Replicator manager) • 5.6+ utilities: mysqlfailover, mysqlrpladmin




16.GitHub https://github.com/blog/1261-github-availability-this-week

17.Fully automated failover a good idea? • False alarms • Repeated failover • Overloaded master? MHA doesn’t allow a failover within 8h, unless —last_failover_min=n is set • Data loss • id=103 latest, relay logs at id=101 => loss • group commit in the binary log • Split brain

18.Proxies • MariaDB MaxScale • Popular use: load balancing Galera clusters • MySQL Router + MySQL Fabric • ProxySQL • Used alongside Galera clusters too • Included with Percona XtraDB Cluster 5.7


20.Sharding • SPIDER • Tungsten Replicator • Tumblr JetPants

21.Vitess • Servers & tools to scale MySQL for web written in Go • Has MariaDB support too (*) • Python client interface • DML annotation, connection pooling, shard management, workflow management, zero downtime restarts • Become super easy to use: http://vitess.io/ (with the help of Kubernetes)

22.Failwhales • Twitter started on MySQL, and is still MySQL - you just need to “evolve” • Gizzard (sharding), Mesos + Apache Cotton • Digg started on MySQL, migrated to Cassandra, and came back to MySQL

23.Security • Philippines voter data leave 55m at risk: 338GB MySQL dump • Ashley Madison: 6.9GB compressed dump, 36m email addresses leaked, 9.6m credit card transactions • Patreon: 13.7GB MySQL dump, 99 tables

24.Mossack Fonseca: Panama Papers

25.Prevent SQL injections • MariaDB MaxScale database firewall filter • Configurable filter actions on rule match (Allow the query, block the query or ignore the match), Logging of matching and/or non- matching queries • MySQL Enterprise firewall • ProxySQL

26.Encryption at rest • MariaDB Server 10.1: table or tablespace encryption • design goal: Encrypt all user data that may touch the disk — InnoDB data, InnoDB logs, binary logs, temporary tables, temporary files • key management on the filesystem? [no key rotation] Amazon KMS? • caveats: mysqlbinlog needs work with encrypted binlogs; Galera Cluster gcache isn’t encrypted • MySQL 5.7: only encrypts InnoDB tablespaces (innodb_file_per_table; logs unencrypted)

27.In conclusion… • Use semi-sync replication with a failover solution that ensures you don’t failover too often • Make good backups. Test them. Save them. • You’ll most definitely need to shard your data, use proven frameworks and get a proxy involved. Complete backups with multi- source replication when needed. • Use mysqldump and xtrabackup together (and mydumper for parallel backup/restore; mysqlpump) • Security is key: prevent SQL injections, encrypt your data at rest

28.It’s 2016, you don’t want this…

29.Percona Monitoring and Management (PMM) • http://pmmdemo.percona.com/