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It is with great pleasure, I can announce that a new book dedicated to MySQL NDB Cluster has just been released. The book Pro MySQL NDB Cluster is written by my colleague Mikiya Okuno and myself and is a nearly 700 pages deep dive into the world of MySQL NDB Cluster. The book is published by Apress.

Tip: There are several ways to cluster MySQL. This book is about the product MySQL Cluster (often called MySQL NDB Cluster to clarify which cluster it is). There is also MySQL InnoDB Cluster, …

Join Percona Chief Evangelist Colin Charles as he covers happenings, gives pointers and provides musings on the open source database community.

We’re close to opening up the call for papers for Percona Live Santa Clara 2018 and I expect this to happen next week. We also have a committee all lined up and ready to vote on submissions.

In other news, I’ve spent some time preparing for the Korean MySQL Power Group meetup to be held in Seoul this Saturday, 11 November 2017. This is a great opportunity for us to extend our reach in Asia. This meetup gathers together top DBAs from Internet companies that use MySQL and related technologies.

Gartner has released their Magic Quadrant …

Most organizations do not realize they have a problem with database backups until they need to restore the data and find it’s not there or not in the form that they were expecting.

The designated administrator managing the database environments must be prepared for situations where any failure may cause an impact to the availability, integrity, or usability of a database or application. Reacting to these failures is a key component of the administrator’s responsibilities and their ability to react correctly depends on whether they have a well-planned strategy for database backups and recovery.

Pixar’s “Toy Story 2” famously almost never happened due a command line mis-run causing the movie to be deleted and an in-effective backup strategy in place. That movie went on to …

In this blog post, I’ll look at MySQL and Linux context switches and what is the normal number per second for a database environment.

You might have heard many times about the importance of looking at the number of context switches to indicate if MySQL is suffering from the internal contention issues. I often get the question of what is a “normal” or “acceptable” number, and at what point should you worry about the number of context switches per second?

First, let’s talk about what context switches are in Linux. This StackOverflow Thread provides a good discussion, with a lot of details, but basically it works like this:  

The process (or thread in MySQL’s case) is running its computations. Sooner or later, it has to do some blocking operation: disk IO, network IO, block waiting on a mutex …

Ok, so now we’re got our InnoDB Cluster a-clustering, MySQL Router a-routing, now we need some disaster to be a-disaster-recovering…

A foreword first.

If you’re looking to use Enterprise Backup to recover a single node and restore that node back into an existing InnoDB Cluster, LeFred takes you through that one nicely here.

Preparing for backup

On our single primary server, the one that allows write, which was ic2/10.0.0.12 in my case:

mysql -uroot -poracle << EOF 
SET sql_log_bin = OFF; 
 create user 'backup'@'%' identified by 'oracle';
 grant all on *.* to 'backup'@'%';
SET sql_log_bin = ON; 
EOF

Let’s create something to backup (if you haven’t already done so of course):

mysqlsh --uri …

Want to setup InnoDB Cluster and be prepared for a Disaster Recovery scenario? Get ready:

Here’s a way to set up InnoDB Cluster using the 3 environments, on Oracle Linux 7.2, 5.7.19 MySQL Commercial Server, MySQL Shell 8.0.3 DMR, MySQL Router. As this is the first blog post for a complete disaster recovery scenario of InnoDB Cluster, we’ll also be installing MySQL Enterprise Backup.

If you’re new to InnoDB Cluster then I’d highly recommend looking at the following to understand how it works and what Group Replication, Shell & Router are.:

• https://dev.mysql.com/doc/refman/5.7/en/mysql-innodb-cluster-production-deployment.html
• …

Sometimes when you are using a MySQL InnoDB Cluster, you might encounter some performance issue because one node becomes dramatically slow.

Why ?

First of all, why ? A node can apply the transactions slower than the other nodes for many different reasons. The most frequents are for example, slower disks (remember, it’s advised to have nodes with the same specifications), but if you are using a RAID controller with a BBU, during the learning cycle, the write performance can decrease by 10 or even more. Another example could be an increase of IO operations that will flood the full IO capacity of the system. Making a local backup or sharing the server resources with some other components could lead in such behavior.

Flow Control

To avoid to have a node lagging to much behind and try to sustain the same throughput all over the cluster, Group Replication uses a flow control mechanism ( …

Introduction Last week, one of my blog readers asked me of a way to reuse the @Id mapping so that it won’t have to be declared on each an every entity. Because this is a good opportunity to introduce @MappedSuperclass, I decided to answer the question with a blog post. Domain Model Assuming we are … Continue reading How to inherit properties from a base class entity using @MappedSuperclass with JPA and Hibernate →

Last time we looked at SKIP LOCKED where rows locked by another process were skipped. NOWAIT informs the server to return immediately IF the desired rows can not be locked.

How To Use NOWAIT Start a connection to your MySQL 8 server, start a transaction, and make a query to lock up part of the data. mysql>START TRANSACTION; mysql>SELECT * FROM city WHERE countryCode = 'USA' FOR UPDATE;
On a second connection, start a transaction and issue a SELECT query with NOWAIT. mysql>START TRANSACTION; mysql>SELECT * FROM city WHERE countryCode = 'USA' FOR UPDATE NOWAIT;
The second connection will get a message saying 'statement aborted because lock(s) could not be acquired immediately and NOWAIT is SET
So if you can come back later to lock the records or just can not …

Having a load balancer or reverse proxy in front of your MySQL or MariaDB server does add a little bit of complexity to your database setup, which might lead to some, things behaving differently. Theoretically, a load balancer which sits in front of MySQL servers (for example an HAProxy in front of a Galera Cluster) should just act like a connection manager and distribute the connections to the backend servers according to some balancing algorithm. MySQL, on the other hand, has its own way of managing client connections. Ideally, we would need to configure these two components together so as to avoid unexpected behaviours, and narrow down the troubleshooting surface when debugging issues.

If you have such setup, it is important to understand these components as they can impact the overall performance of your database service. In this blog post, we will dive into MySQL's max_connections and HAProxy maxconn options …