The latest from the MySQL community

If you were unable to attend the live webinar (or you want to go back and listen to it again) then it’s now available to view on-line here.

Databases are the center of today’s web and enterprise applications, storing and protecting an organization’s most valuable assets and supporting business-critical applications. Just minutes of downtime can result in significant lost revenue and dissatisfied customers. Ensuring database highly availability is therefore a top priority for any organization. Tune into this webcast to learn more.

The session discusses:

1. Causes, effect and impact of downtime
2. Methodologies to map applications to HA solution
3. Overview of MySQL HA solutions …

Detecting conflicts

Part of the latest MySQL Cluster Development Milestone Release (MySQL Cluster 7.2.1 – select the “Development Release” tab at http://dev.mysql.com/downloads/cluster/#downloads) is a couple of enhancements to the conflict detection and resolution mechanism for active-active (multi-master) replication. While MySQL Cluster has had conflict detection for years it has now been made much more complete and a lot easier to use:

• No changes needed to the application schema
• Entire conflicting transaction is rolled back together with any dependent transactions

The focus of this post will be to step through how to use this feature – while it will also attempt to explain how it works at …

Stockholm - October 4th 2011

Severalnines, provider of automation and management software for easily usable, highly available and auto-scalable cloud database platforms, today announces the latest release of its flagship product ClusterControl™ for MySQL Replication.

Introducing ClusterControl™ for MySQL Replication v.1.1.9

ClusterControl™ for MySQL Replication enables customers to Deploy, Manage, Monitor and Scale a clustered database platform based on the standard MySQL Replication.

Developers and DBAs now have access to all of the features of Severalnines' flagship product ClusterControl™ specifically adapted to MySQL Replication.
…

I will be presenting on MySQL Cluster and MySQL Replication at the Oracle Technical Network MySQL Developer day in London on Tuesday, 18 October 2011 (8:30 AM – 4:00 PM). It’s free but you need to register here while there are still places (attendance has been extremely high at other locations).

The MySQL Developer Day is a one-stop shop for you to learn all the essential MySQL skills. In this free, one-day seminar, we will cover everything you need to know to successfully design, develop, and manage your MySQL databases. You’ll also learn the guidelines and best practices in performance tuning and scalability.

Attend this event and gain the knowledge to: …

Scalability is about application, architecture and infrastructure design, and careful management of server components.

1. Object Relational Mappers

ORMs are popular among developers but not among performance experts.  Why is that?  Primarily these two engineers experience a web application from entirely different perspectives.  One is building functionality, delivering features, and results are measured on fitting business requirements.  Performance and scalability are often low priorities at this stage.  ORMs allow developers to be much more productive, abstracting away the SQL difficulties of interacting with the backend datastore, and allowing them to concentrate on building the features and functionality.

On the performance side the picture is a bit different.  By leaving SQL query writing to an ORM, you are faced with complex queries that the database cannot optimize …

There are a lot of scalability challenges we see with clients over and over. The list could easily include 20, 50 or even 100 items, but we shortened it down to the biggest five issues we see.

1. Tune those queries

By far the biggest bang for your buck is query optimization. Queries can be functionally correct and meet business requirements without being stress tested for high traffic and high load. This is why we often see clients with growing pains, and scalability challenges as their site becomes more popular. This also makes sense. It wouldn't necessarily be a good use of time to tune a query for some page off in a remote corner of your site, that didn't receive real-world traffic. So some amount of reactive tuning is common and appropriate.

Enable the slow query log and watch it. Use …

I was debugging a performance problem and was shocked that while overnight we had the same slow query run on a replica, it wasnt logged to the slow log that I set up the day prior.
It seems slow queries that are executed from the replication SQL thread are not logged. I did not know this. This is how I confirmed this is the case:

*****SLAVE SERVER*****enable slow log and confirm its working
mysql> set @@global.slow_query_log=ON;Query OK, 0 rows affected (0.00 sec)
mysql> set @@global.long_query_time=1;Query OK, 0 rows affected (0.00 sec)
mysql> flush logs;Query OK, 0 rows affected (0.12 sec)
mysql> select sleep(10);+-----------+| sleep(10) |+-----------+| 0 |+-----------+1 row in set (10.00 sec)
mysql> Ctrl-C -- exit!Abortedslave:~# cd /databases/logsslave:/databases/logs# tail mysqld-slow.log /usr/sbin/mysqld, Version: 5.1.45-89.lenny.52-log ((Percona SQL Server (GPL), XtraDB …

The announcements at the O'Reilly MySQL and Oracle Collaborate conferences last week mark an exciting milestone in the development of MySQL replication.  The purpose of this blog is to summarize those announcements and provide links to further reading, published directly by the engineers who have been working hard to take MySQL replication to the next level.

A number of significant replication enhancements were released as part of the MySQL 5.5 GA just a few months ago. 
We are always listening to our customers and the community.  And, based on their input, the MySQL engineering team has continued to rapidly evolve replication functionality - enabling new classes of applications to rely on MySQL for their …

The announcements at the O'Reilly MySQL and Oracle Collaborate conferences last week mark an exciting milestone in the development of MySQL replication.  The purpose of this blog is to summarize those announcements and provide links to further reading, published directly by the engineers who have been working hard to take MySQL replication to the next level.

A number of significant replication enhancements were released as part of the MySQL 5.5 GA just a few months ago. 
We are always listening to our customers and the community.  And, based on their input, the MySQL engineering team has continued to rapidly evolve replication functionality - enabling new classes of applications to rely on MySQL for their fastest …

The new Development Release for MySQL 5.6 contains a great feature that our users have been asking for for a while (work log 344 first raised in 2010!) – delayed replication.

Stop mistake being propagated

The concept (and as you’ll see the execution) is extremely simple. If a user makes a mistake on the master – such as dropping some critical tables – then we want to give them the opportunity to recover the situation by using the data held on one of the slaves. The problem is that the slave is busily trying to keep up with the master and in all likelihood will have dropped these tables before the user has time to pull the plug on the replication stream. What this feature does is give the DBA the option to introduce a configurable …