September 22, 2014

MySQL Connection Timeouts

Sometimes on very busy MySQL server you will see sporadic connection timeouts, such as Can’t connect to MySQL server on ‘mydb’ (110). If you have connects timed in your application you will see some successful connections taking well over the second. The problem may start very slow and be almost invisible for long time, for […]

What Causes Downtime in MySQL?

We’ve just published a new white paper analyzing the causes of emergency incidents filed by our customers. The numbers contradict the urban myth that bad SQL is the most common problem in databases. There are a number of surprises in other areas, too, such as the causes of data loss. This is the companion to […]

How to estimate query completion time in MySQL

Have you ever run a query in MySQL and wondered how long it’ll take to complete? Many people have had this experience. It’s not a big deal until the query has been running for an hour. Or a day and a half. Just when IS that query going to finish, anyway? There are actually a […]

MySQL net_write_timeout vs wait_timeout and protocol notes

In my previous post I mentioned you might need to increase net_write_timeout to avoid connection being aborted and now I think I should have better explained that. MySQL uses a lot of different timeout variables at different stages. For example when connection is just being established connect_timeout is used. When server waits for another query […]

Backport of micro-time patch to mysql 4.1

Taking into account 4.1 tree is still popular and is used on many production servers we decided to make backport of patch to slow-log queries. The patch allows to specify time of slow queries in microseconds and is very helpful in a fight with problematic queries. 4.1 Patch is available here (The original patch was […]

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 […]

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. […]

Using MySQL 5.6 Global Transaction IDs (GTIDs) in production: Q&A

Thank you to all of you who attended my webinar last week about Global Transaction IDs (GTIDs), which were introduced in MySQL 5.6 to make the reconfiguration of replication straightforward. If you missed my webinar, you can still listen to the recording and download the sides (free). We had a lot of questions during the […]

MySQL 101: Monitor Disk I/O with pt-diskstats

Here on the Percona Support team we often ask customers to retrieve disk stats to monitor disk IO and to measure block devices iops and latency. There are a number of tools available to monitor IO on Linux. iostat is one of the popular tools and Percona Toolkit, which is free, contains the pt-diskstats tool […]

Migrating to Percona XtraDB Cluster 2014 edition: Sept. 10 MySQL webinar

Join me online next week (September 10 at 10 a.m. PDT) for my live webinar on Migrating to Percona XtraDB Cluster.  This was a popular webinar that I gave a few years ago, so I’m doing it again with updates for Percona XtraDB Cluster 5.6 (PXC) and all the latest in the Galera world. This webinar […]