Overview The Skinny

Part of the power of Tungsten Clustering for MySQL / MariaDB is the ability to perform true zero-downtime maintenance, allowing client applications full access to the database layer, while taking out individual nodes for maintenance and upgrades. In this blog post we cover various types of maintenance scenarios, the best practices associated with each type of action, and the key steps to ensure the highest availability.

Important Questions Understand the Environment as a Whole First

There are a number of questions to ask when planning cluster maintenance that are critical to understand before starting.

For example:

1. What is the cluster topology?
   • Standalone (connectors write to single cluster master)
     Single cluster: …

The Question Recently, a customer asked us:

How would we manually move the relay role from a failing node to a slave in a Composite Tungsten Cluster passive site?

The Answer The Long and the Short of It

There are two ways to handle this procedure manually when the usual switch command fails to work as expected. One is short and reasonably automated, and the other is much more detailed and manual.

Of course, the usual procedure is to just issue the switch command in the passive cluster:

use west
set policy maintenance
switch
set policy automatic

The below article describes what to do when the switch command does not move the relay role to another node.

SHORT

Below is the list of cctrl commands that would be run for the basic, short version, which (aside from handling policy changes) is really only three …

Instead of using the old DriverManager its the better way to use the DataSource class to get a connection to a MySql Database. This can be done by geting it from the app server container or by creating and configuration it directly from the driver. Get the MySQL datasource from the app container Context context [...]