November 23, 2014

How a set of queries can be killed in MySQL using Percona Toolkit’s pt-kill

You might have encountered situations where you had to kill some specific select queries that were running for long periods and choking the database. This post will go into more detail with an example of report query offloading. Report query (select) offloading to a slave server is a common practice to reduce the workload of the […]

Avoiding MySQL ALTER table downtime

MySQL table alterations can interrupt production traffic causing bad customer experience or in worst cases, loss of revenue. Not all DBAs, developers, syadmins know MySQL well enough to avoid this pitfall. DBAs usually encounter these kinds of production interruptions when working with upgrade scripts that touch both application and database or if an inexperienced admin/dev […]

MySQL’s INNODB_METRICS table: How much is the overhead?

Starting with MySQL 5.6 there is an INNODB_METRICS table available in INFORMATION_SCHEMA which contains some additional information than provided in the SHOW GLOBAL STATUS output – yet might be more lightweight than PERFORMANCE_SCHEMA. Too bad INNODB_METRICS was designed during the Oracle-Sun split under MySQL leadership and so it covers only InnoDB counters. I think this […]

MySQL community set to meet at Percona Live London 2014

The countdown is on for Europe’s largest annual MySQL event, Percona Live London 2014. The two days of technical tutorials and sessions, November 3-4, will focus on the latest MySQL industry trends, news, best practices – and a look at what’s on the near- and long-term horizon within the global MySQL ecosystem. Percona Live London […]

Innodb transaction history often hides dangerous ‘debt’

In many write-intensive workloads Innodb/XtraDB storage engines you may see hidden and dangerous “debt” being accumulated – unpurged transaction “history” which if not kept in check over time will cause serve performance regression or will take all free space and cause an outage. Let’s talk about where it comes from and what can you do […]

How to avoid hash collisions when using MySQL’s CRC32 function

Percona Toolkit’s  pt-table-checksum performs an online replication consistency check by executing checksum queries on the master, which produces different results on replicas that are inconsistent with the master – and the tool pt-table-sync synchronizes data efficiently between MySQL tables. The tools by default use the CRC32. Other good choices include MD5 and SHA1. If you have installed the FNV_64 user-defined function, pt-table-sync will […]

MySQL Replication: ‘Got fatal error 1236′ causes and cures

MySQL replication is a core process for maintaining multiple copies of data – and replication is a very important aspect in database administration. In order to synchronize data between master and slaves you need to make sure that data transfers smoothly, and to do so you need to act promptly regarding replication errors to continue […]

MySQL upgrade best practices

MySQL upgrades are necessary tasks and we field a variety of questions here at Percona Support regarding MySQL upgrade best practices. This post highlights recommended ways to upgrade MySQL in different scenarios. Why are MySQL upgrades needed? The reasons are many and include: Access to new features, performance benefits, bug fixes…. However, MySQL upgrades can […]

Galera data on Percona Cloud Tools (and other MySQL monitoring tools)

I was talking with a Percona Support customer earlier this week who was looking for Galera data on Percona Cloud Tools. (Percona Cloud Tools, now in free beta, is a hosted service providing access to query performance insights for all MySQL uses.) The customer mentioned they were already keeping track of some Galera stats on Cacti, and […]

mysqld_multi: How to run multiple instances of MySQL

The need to have multiple instances of MySQL (the well-known mysqld process) running in the same server concurrently in a transparent way, instead of having them executed in separate containers/virtual machines, is not very common. Yet from time to time the Percona Support team receives a request from a customer to assist in the configuration of […]