Shinguz's blog

We had a Galera Cluster support case recently. The customer was drenched in tears because his Galera Cluster did not work any more and he could not make it work any more.

Hello thatsafunnynamecomment,

Thanks for reading and correcting my findings! You are absolutely right. I did a bit short-cut too much in maths!

In MySQL we have the typical behaviour that we open and close connections very often and rapidly. So we have very short-living connections to the server. This can lead in extreme cases to the situation that the maximum number of TCP ports are exhausted.

It took me quite a while to find out how the beast Galera Arbitrator (garbd) works. To safe your time here a short summary:

Our bigger customers where we help to deploy Galera Cluster for MySQL set-ups have some commercial hardware (e.g. F5 or Cisco) for load balancing instead of software load balancers.

Recently a forum question
[ 1
] got my attention:

Maybe you experienced some strange behaviour with MySQL: Everything is installed correctly and should work. But it does not.

Recently we had to set-up a 3-node Galera Cluster with a Load Balancer in front of it. Because Galera Cluster nodes (mysqld) still reply to TCP requests on port 3306 when they are expelled from the Cluster it is not sufficient to just leave it to the Load Balancer to check the port if a Galera node is properly running or not.

You are running already MariaDB or MySQL databases in production but you have higher requirements in database availability? If you want to solve these High Availability requirements with Galera Cluster this training is the right one for you.

FromDual is looking for professional, enthusiastic and experienced people who:

Switching from MySQL/MyISAM to Galera Cluster requires that all tables (except those from the mysql, information_schema and performance_schema) are using the InnoDB Storage Engine.

From time to time some maintenance work on the MySQL database has to be done. During the maintenance window we do not want to have application traffic on the database.

The mpm agent writes a lock file to prevent that several instances are running at the same time and piling up and possibly slow down the system.

A while ago it was pretty inconvenient to start a complete Galera Cluster from scratch. Rolling restart an such things are already working well but bootstrapping was a pain.

Copy a directory structure from one to an other server:

Some MySQL customers do not want to use the root user for mysqldump backups. For this user you have to grant the following minimal MySQL privileges:

In this weeks MySQL workshop we were discussing, beside other things, about the innodb_file_per_table parameter and its advantages of enabling it. In addition there was a discussion if the InnoDB system tablespace file can be shrinked once it has been grown very large or not. We all know the answer: The InnoDB system tablespace file does never shrink again.

MySQL hosting providers can easily loose the overview over their customers and which user or schema is still in use and which not.

When a MySQL Slave is set-up with mysqldump you have 2 possibilities:

Important: Before you start any operation mentioned below do a proper file system backup of your XFS file system you want to resize. If MySQL is running on this mount point do this with a stopped mysqld. Alternatively you can also use mysqldump to do the MySQL backup but test the restore time before continuing to not experience ugly surprises…