Even if a Galera node looks like a regular MySQL server, the underlying replication mechanism is very different. This implies some changes in the way you have to configure the Galera nodes. Here are some of the most common misconceptions about Galera when using Percona XtraDB Cluster.

Q: Why should I enable binary logging as it is not needed by Galera replication?
Unlike for regular asynchronous MySQL replication, it is true that you don’t need to enable binary logging to use Galera replication. However what if someone runs an accidental DROP TABLE?

In this case, the statement will be replicated immediately on all nodes. Then your main option to recover lost data is to use a backup. But if binary logging is not …

One of the big announcements at the Amazon Web Services re:Invent 2014 conference this week was the unveiling of Aurora. The result of years of internal work, Aurora, currently in preview, is a MySQL 5.6-compatible option that “combines the speed and availability of high-end commercial databases with the simplicity and cost-effectiveness of open source databases” on the AWS infrastructure. The Aurora database engine will be made available through the Amazon RDS for Aurora service. This new database option is another example of the vibrant innovation coming from the MySQL ecosystem and key role that relational databases play in applications of today and …

Did your logging stop working after you set up logrotate? Then this post might be for you.

Archive your log files!

Some time ago, Peter Boros wrote about Rotating MySQL Slow Logs safely, explaining the steps of a “best practice” log rotate/archive. This post will add more info about the topic.

When running logrotate for MySQL (after proper setting the /etc/logrotate.d/mysql conf file) from anacron, there’s a situation that you might potentially face if the user and password used to execute the “flush logs” command is stored in, for example, /root/.my.cnf file.

The situation:

You might find out that you have a new MySQL log file ready to receive data, but nothing is being written to it.

Why did this happen?

The logrotate script is executed, but the postrotate …

A deadlock in MySQL happens when two or more transactions mutually hold and request for locks, creating a cycle of dependencies. In a transaction system, deadlocks are a fact of life and not completely avoidable. InnoDB automatically detects transaction deadlocks, rollbacks a transaction immediately and returns an error. It uses a metric to pick the easiest transaction to rollback. Though an occasional deadlock is not something to worry about, frequent occurrences call for attention.

Before MySQL 5.6, only the latest deadlock can be reviewed using SHOW ENGINE INNODB STATUS command. But with Percona Toolkit’s pt-deadlock-logger you can have deadlock information retrieved from SHOW ENGINE INNODB STATUS at a given interval and saved to a file or table for late diagnosis. For more information on using pt-deadlock-logger, see …

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 data synchronization. Here on the Percona Support team, we often help customers with replication broken-related issues. In this post I’ll highlight the top most critical replication error code 1236 along with the causes and cure. MySQL replication error “Got fatal error 1236” can be triggered by multiple reasons and I will try to cover all of them.

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I’ve recently worked with customers using replication rings with 4+ servers; several servers accepting writes. The idea behind this design is always the same: by having multiple servers, you get high availability and by having multiple writer nodes, you get write scalability. Alas, this is simply not true. Here is why.

High Availability

Having several servers is a necessary condition to have high availability, but it’s far from sufficient. What happens if for instance C suddenly disappears?

• The replication ring is broken, so updates from A and B will never go to D. D will then quickly become so out-of-date that it’s not going to be usable. But wait! A will no longer receive the updates from B so A …

HAProxy is frequently used as a load-balancer in front of a Galera cluster. While diagnosing an issue with HAProxy configuration, I realized that logging doesn’t work out of the box on CentOS 6.5. Here is a simple recipe to fix the issue.

If you look at the top of /etc/haproxy/haproxy.cfg, you will see something like:

global
    log         127.0.0.1 local2
[...]

This means that HAProxy will send its messages to rsyslog on 127.0.0.1. But by default, rsyslog doesn’t listen on any address, hence the issue.

Let’s edit /etc/rsyslog.conf and uncomment these lines:

$ModLoad imudp
$UDPServerRun 514

This will make rsyslog listen on UDP port 514 for all IP addresses. Optionally you can limit to 127.0.0.1 by adding:

$UDPServerAddress …

Recently I encountered a specific situation in which a customer was forced to stay with the MyISAM engine due to a legacy application using tables with over 1000 columns. Unfortunately InnoDB has a limit at this point. I did not expect to hear this argument for MyISAM. It is usually about full text search or spatial indexes functionality that were missing in InnoDB, and which were introduced in MySQL 5.6 and 5.7, respectively, to let people forget about MyISAM. In this case though, InnoDB still could not be used, so I gave the TokuDB a try.

I’ve created a simple bash script to generate a SQL file with …

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 be risky if not tested extensively beforehand with your application because the process might break it, prevent the application from functioning properly – or performance issues could arise following the upgrade. Moreover, I suggest keeping an eye on new releases of MySQL and Percona Server – check what has changed in the …

Over the past few months, I’ve seen an increase in the following use case while working on performance and schema review engagements:

I need to store exponentially increasing amounts of data and analyze all of it in real-time.

This is also known simply as: “We have big data.” Typically, this data is used for user interaction analysis, ad tracking, or other common click stream applications. However, it can also be seen in threat assessment (ddos mitigation, etc), financial forecasting, and other applications as well. While MySQL (and other OLTP systems) can handle this to a degree, it is by no means a forte. Some of the pain points include:

• Cost of rapidly increasing, expensive disk storage (OLTP disks need to be fast == $$)
• Performance decrease as the data size increases …