Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
Mydbops, profile picture
Uploaded byMydbops
2,639 views

Galera cluster for high availability

The document discusses high availability (HA) solutions for MySQL, particularly focusing on Galera cluster technology. It covers the principles of distributed computing, various HA solutions, and the features of Galera, such as synchronous multi-master replication, automated node recovery, and load balancer considerations. Additionally, it addresses node recovery procedures, including incremental and state snapshot transfers, and outlines best practices for implementation.

Internet◦
Downloaded 59 times
MySQL Consulting Team Galera Cluster for High Availability
About MyDBOPS •  MySQL Consulting •  MySQL Support •  Remote DBA support. •  Expert MySQL solutions. •  24/7 MySQL Monitoring and Support •  MariaDB, Percona, Galera, TokuDB were supported too.
Agenda •  Need for HA •  Principle of Distributed computing. •  MySQL HA Solutions Available. •  Introduction to Galera. •  Percona Cluster. •  Node Recovery. •  Backup and Recovery. •  Load Balancers. •  Things to be considered.
Need For HA •  Site Reliability. •  Ensure Uptime •  Failover. •  Disaster Recovery. •  Scheduled / Unscheduled downtime. •  Avoid Single Point Failure
Principle of Distributed Computing CAP Theorem Consistency , Availability and Partitioning Only Two out of three is possible in any distributed computing system. AP – MySQL Replication CA – Galera Cluster
Principle of Distributed Computing CAP Theorem
MySQL HA Solutions Available •  Master – Slave •  Master – Master •  Single Writer •  NDB Cluster ( Oracle MySQL ) •  Galera Cluster •  Tungsten Replicator •  Storage Level Replication ( DRDB)
Introduction to Galera •  Founded By Codership •  Synchronous Replication •  Parallel Replication •  Multi-Threaded •  Automated node recovery •  Zero slave lag •  Read/ Write Scalable •  WAN Based Optimization ( Galera 3.0) •  A True Open Source. •  Support InnoDB and TokuDB ( MyISAM Experimental )
Introduction to Galera What is Galera ? Galera is a replication plugin for the synchronous and multi- master replication to achieve HA. “Wsrep_provider_options” controls library. Available Distributions •  Percona XtraDB Cluster •  MariaDB Cluster •  As a plugin over MySQL • 
Introduction to Galera •  Shared nothing Architecture. •  Network is the heart. What is wsrep ? (Write Set REPlication ) It is an API to connect the Galera library and control characteristics. It helps to implement synchronous replication and certification based multi-master-replication.
Introduction to Galera Simple Architecture
•  Use Galera Library •  XtraDB •  Xtrabackup = + + Percona Cluster
Percona Cluster Why Percona Server ? •  Enhanced InnoDB (XtraDB ) •  Performance Improvement •  Xtrabackup-v2 ( Makes SST better ) •  Better Bug fixes. •  A better MySQL for scalability. •  Aligned with Oracle MySQL with better instrumentation and performance patches.
Transaction in Galera •  Transaction is handled by Galera Plugin. •  Uses traditional dual phase commit. •  It also handles locking. •  Uses the optimistic locking method. •  The commits are based on certifications (keys). •  Smaller transaction are always better. •  Increase in network latency increases query time. •  Support InnoDB and TokuDB. MyISAM is still experimental.
Transaction in Galera
Transaction in Galera •  Synchronous ( Virtual ) Replication. •  Wsrep_causal_reads=ON ( true synchronous). •  Auto_increment_* is handled by cluster. •  Uses GTID for Transaction. ( Not the GTID in MySQL 5.6 ) •  Transaction latency increases with increase in nodes.
Galera Ports As Galera is complex beyond standard MySQL .It needs multiple ports too for its successful operation •  3306: Standard MySQL port •  4567: Group Communication •  4568: IST •  4444: SST The firewall rule can be designed based these ports.
Node Recovery •  Node recovery is automated. •  Validates the gcache for state files. •  Chooses the State Transfer method 1) IST (Incremental State Transfer) 2) SST (State Snapshot Transfer )
Node Recovery IST : • Recover from write sets in gcache ( memory ). • Faster recovery method. • Have good gcache size. • Does affect the node state.
Node Recovery SST : State Snapshot Transfer the complete transfer ( Cloning ) of data to recreate a node. u  When not in Gcache ( wsrep_local_cached_downto) u  Adding a new node Different Methods of SST Xtrabackup-v2 (best ) , rsync , mysqldump .
Node Recovery SST : u  SST will cause a node in cluster to Donor state. u  Donor selection is automatic. u  Donor selection can be forced by wsrep_sst_donor Hack: SST can be avoided by Full and Incremental hot backups in node recovery. ( It forces the IST ). Blog by Jay Janssen on bypassing SST.
Node Recovery Validate Node after recovery Wsrep_local_state=4 Wsrep_local_state_Comment 1) Joining 2) Donor/desynced 3) Joined 4) Synced
Wsrep_local_state_Comment 1) Joining : Initial state of node 2) Donor/desynced : Huge delay in replication write set 3) Joined : Delay less than 1000 write sets 4) Synced : Sync with all nodes Node Recovery
Load Balancers •  HAProxy •  Pen Proxy •  Galera Load Balancer ( based on Pen ) •  Max Scale •  ProxySQL Note : Make sure Load Balancer aware of the Galera State. Use the appropriate Load balancer Algorithm.
Things should be considered •  Support only Transactional engines. •  Row Based replication. •  Read committed Isolation. •  Innodb_autoinc_lock_mode=2. •  Avoid huge transactions. •  Wsrep_max_ws_rows (128K) •  Wsrep_max_ws_size. (1G) •  Network is the heart. •  Keep the DB design simple
Things should be considered •  Foreign Keys can cause error ( Bug ) •  Maintain Quorum •  Check for application error after commit •  Keep odd number of nodes
IMAGE Courtesy • Galera and Percona cluster documentation • http://opentodo.net/2012/12/mysql-multi-master-replication-with- galera/
Thanks!!! Email : mysqlsupport@mydbops.com