July 28, 2014

Check for MySQL slave lag with Percona Toolkit plugin for Tungsten Replicator

A while back, I made some changes to the plugin interface for pt-online-schema-change which allows custom replication checks to be written. As I was adding this functionality, I also added the –plugin option to pt-table-checksum. This was released in Percona Toolkit 2.2.8. With these additions, I spent some time writing a plugin that allows Percona […]

How to identify and cure MySQL replication slave lag

Here on the Percona MySQL Support team, we often see issues where a customer is complaining about replication delays – and many times the problem ends up being tied to MySQL replication slave lag. This of course is nothing new for MySQL users and we’ve had a few posts here on the MySQL Performance Blog […]

utf8 data on latin1 tables: converting to utf8 without downtime or double encoding

Here’s a problem some or most of us have encountered. You have a latin1 table defined like below, and your application is storing utf8 data to the column on a latin1 connection. Obviously, double encoding occurs. Now your development team decided to use utf8 everywhere, but during the process you can only have as little […]

Reasons for run-away main Innodb Tablespace

So you’re running MySQL With innodb_file_per_table option but your ibdata1 file which holds main (or system) tablespace have grown dramatically from its starting 10MB size. What could be the reason of this growth and what you can do about it ? There are few things which are always stored in main tablespace – these are […]

Resyncing table on MySQL Slave

Sometimes MySQL Replication may run out of sync – because of its own buts or operational limitations or because of application mistake, such as writing to the slave when you should be only writing to the master. In any case you need slave to be synced with Master. To discover the difference between Master and […]

Should you name indexes while doing ALTER TABLE ?

MySQL Server does not require you to specify name of the index if you’re running ALTER TABLE statement – it is optional. Though what might be good practical reasons to specify the key name or omit ? Things what you should be looking at is how MySQL names indexes automatically as well as what maintaining […]

Can MySQL temporary tables be made safe for statement-based replication?

A while ago I wrote about how to make MySQL replication reliable, part of which is to eliminate temporary tables. The idea is this: if a slave is stopped (or crashed) while a temporary table is open and is then restarted, the temporary table doesn’t exist anymore, and the slave will have problems trying to […]

Using MMM to ALTER huge tables

Few months ago, I wrote about a faster way to do certain table modifications online. It works well when all you want is to remove auto_increment or change ENUM values. When it comes to changes that really require table to be rebuilt – adding/dropping columns or indexes, changing data type, converting data to different character […]

Managing Slave Lag with MySQL Replication

The question I often get is how far MySQL may fall behind and how to keep replication from lagging. The lag you will see will vary a lot from application to the application and from load to load. Plus what is the most important within same application the lag will likely have spikes – most […]

Doing a rolling upgrade of Percona XtraDB Cluster from 5.5 to 5.6

Overview Percona XtraDB Cluster 5.6 has been GA for several months now and people are thinking more and more about moving from 5.5 to 5.6. Most people don’t want to upgrade all at once, but would prefer a rolling upgrade to avoid downtime and ensure 5.6 is behaving in a stable fashion before putting all of […]