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 …

This week, MySQL released a feature-preview – the ability to have multiple threads on the slave so that it is better able to keep pace with the updates being applied on the master. To simplify potential sequencing issues, all updates for a particular database will be handled by the same thread – in other words you need to make sure that your application uses multiple databases in order to see the benefits.
Luís Soares (from the development team) has written a great Blog going into the details.

A quick reminder that MySQL is well represented at the Oracle Collaborate conference which starts in Orlando on Sunday.

For those not familiar with Collaborate, it’s the big community conference for Oracle users – this year it’s in Orlando from April 10th through 14th (I’ve just re-checked the weather forecast, 31 Celsius vs. -18 at the last conference I presented at – OOW Beijing in December – what a difference 4 months and 8,000 miles make!).

I’ll be presenting on MySQL Cluster in a session called “Building Highly Available Scalable Real-Time Services with MySQL Cluster” where I’ll focus on:

• Basics of MySQL Cluster – what it does, who uses it and why
• Accessing …

Oracle University has added a new course to its training catalog “Introduction to MySQL 5.5″ which is a day-long seminar. The seminar goes into some detail on many aspects of using MySQL and of course pays particular attention to the new features in MySQL 5.5. I’ve reviewed the material and can assure you that there is plenty of it!

Of most relevance to this blog is the overview of MySQL Cluster (which isn’t a big focus of the seminar as Cluster is currently using MySQL 5.1) and MySQL replication – the highest profile 5.5 feature being asynchronous replication which can make sure that zero updates are lost even if the master fails catastrophically.

At the time of writing, neither the on-line and instructor-led sessions have been scheduled and so you should register an interest here. When OU have …