September 22, 2014

Syncing MySQL slave table with pt-online-schema-change

I recently encountered a situation in which after running Percona Toolkit’s pt-table-checksum on a customer system, 95% of the table on the MySQL master was different on the MySQL slave. Although this table was not a critical part of the infrastructure, from time to time, writes to the table from the master would break replication. […]

Simple MySQL Master HA with mysqlnd_ms

I had the pleasure of presenting to the PHP Users Group Philippines a few days ago about mysqlnd_ms. The mysqlnd plugin, MySQL Master Slave, is a transparent layer on top of mysqlnd extension. This allows you to do read-write splitting and slave reads load balancing without needing to change anything from your application. But do […]

GTIDs in MySQL 5.6: New replication protocol; new ways to break replication

One of the MySQL 5.6 features many people are interested in is Global Transactions IDs (GTIDs). This is for a good reason: Reconnecting a slave to a new master has always been a challenge while it is so trivial when GTIDs are enabled. However, using GTIDs is not only about replacing good old binlog file/position […]

Row-based replication, MySQL 5.6 upgrades and temporal data types

Whither your rollback plan? MySQL 5.6 upgrades are in full swing these days and knowing how to safely upgrade from MySQL 5.5 to 5.6 is important. When upgrading a replication environment, it’s important that you can build a migration plan that safely allows for your upgrade with minimal risk — rollback is often a very […]

Changing an async slave of a PXC cluster to a new Master using 5.6 and GTID

Before Percona XtraBackup 2.1.7 and Percona XtraDB Cluster 5.6.15-25.3, rsync was the only SST method supporting GTID in the way that it was possible to move an asynchronous slave from one Galera node to another one (related bug). Indeed, previous versions of Percona XtraBackup didn’t copy any binary log and due to that, moving the […]

Seconds_Behind_Master fluctuating wildly? Check for events caught in a loop

Recently I was working with a customer where we noticed that Seconds_Behind_Master fluctuating from an expected value of 0 seconds behind to a fairly high six figure value.  The servers were configured in a master-master relationship and used 5 figure server_id values, and we had just migrated this cluster from one data centre to another […]

MySQL 5.6 New Replication Features: Webinar followup Q&A

I want to thank all attendees of my webinar, “MySQL 5.6 New Replication Features: Benefits, Challenges and Limitations“. We had questions that I didn’t have the time to answer: Q: If I run on Amazon’s RDS, do I need to worry about enabling crash-safe slaves, or is that already in place? A: Crash-safe replication is […]

MySQL 5.7 multi-source replication

Recently Oracle announced several new features for the latest available development version of MySQL that is 5.7.2 at the time of writing this article. Most of them are performance and replication related that show us how incredible the new release will be. In this post I’m going to try to explain in some easy steps […]

5 reasons why MySQL replication lag is flapping between 0 and XXXXX

Working day to day with Percona Remote DBA customers, we have been facing an issue from time to time when MySQL replication lag is flapping between 0 and XXXXX constantly – i.e. Seconds_Behind_Master is 0 for a few secs, then it’s like 6287 or 25341, again 0 and so on. I would like to note […]

Crash-resistant replication: How to avoid MySQL replication errors

Percona Server’s “crash-resistant replication” feature is useful in versions 5.1 through 5.5. However, in Percona Server 5.6 it’s replaced with Oracle MySQL 5.6’s “crash safe replication” feature, which has it’s own implementation (you can read more about it here). A MySQL slave normally stores its position in files master.info and relay-log.info which are updated by […]