Continuent Tungsten Stack Targets MySQL Database Replication

Tag : tungsten
Continuent added a replication tool to address the needs of usersof the MySQL open-source database. With the Tungsten Replicator,the company has included a number of features to address challengesaround MySQL database replication for enterprises. Later thismonth, the company plans to add support for Oracle as well.


Continuent wants to plug what it sees as a hole in the market whenit comes to MySQL replication .
Continuent has a long history with MySQL, going back to whenContinuent was called Emic Networks and was focused on providinghigh-availability clustering for the open-source database. Now,Continuent has expanded its open-source stack to include theTungsten Replicator, technology Continuent CEO Eero Teerikorpi saidwill help address long-standing challenges.
MySQLs own replication [technology] is very good and is one ofthe key reason why MySQL adoption is as high as it is, especiallyin Web-based applications, the CEO said. But because of thispopularity, [its] weaknesses have also been very visible and havecreated major headaches for the companies running, for example, onemaster [database] and tens or even hundreds of slaves.
When master databases fail in this type of setup, it creates a lotof manual work and typically fairly long outages in service, hecontinued. Continuent's Tungsten stack helps to run these largersites much more smoothly by providing automatic master failover andonline maintenance and upgrades, he contended.
With Tungsten Replicator, the company has targeted a number ofchallenges around replication laid out by Monty Widenius, an original developer of MySQL, at the 2008MySQL Conference & Expo in Santa Clara, Calif. Specifically,the company has put a bull's eye on MySQL statement replication,proper handling of master failover in presence of multiple slavesfor high availability and checksums on replication events. Inaddition, Continuent also added a table consistency checkmechanism.
We solve the failover problem using global sequence numbers thatallow any slave to connect to any other slave and commencereplicating data, said Continuent CTO Robert Hodges. Morespecifically, we add a sequence number to every request we pick upfrom the logs. The requests are stored in a structure known as atransaction history log [THL], whose contents are copied to slavesand applied there.
The master and each slave agree on the sequence numbers, whichallows slaves to be promoted to master in the event of a failoverbased on who has the highest sequence number. This, Hodgesexplained, is a simple way to pick the most up-to-date slave.
Besides the Tungsten Replicator, the Tungsten stack also includesSequoia, the synchronous multi-master replication project, as wellas Tungsten Manager for cluster-aware service management over LANor WAN, Tungsten Connector for native wire protocol proxying,Bristlecone for scale-out performance testing and Hedera for groupcommunications.
In addition, the company plans to announce support for Oracle Sept.16, and has support for PostgreSQL on its road map for late 2008 orearly 2009 as well.
There will be a follow-up release on Oracle replication within twoweeks, just before Oracle OpenWorld, Teerikorpi said. PostgreSQLis lacking some key features for us to provide our solution to thatmarket, but we are working with the PostgreSQL community to getthis addressed."