Upgrading MariaDB MaxScale from 2.2 to 2.3

This document describes possible issues when upgrading MariaDB MaxScale from version 2.2 to 2.3.

For more information about MariaDB MaxScale 2.3, please refer to the ChangeLog.

Before starting the upgrade, we recommend you back up your current configuration file.

Increased Memory Use

Starting with MaxScale 2.3.0 up to 40% of the memory can be used for caching parsed queries. The most noticeable change is that it improves performance in almost all cases where queries need to be parsed. Most of the time this happens when the readwritesplit router or filters are used.

The amount of memory that MaxScale uses can be controlled with the query_classifier_cache_size parameter. For example, to limit the total memory to 1GB, add query_classifier_cache_size=1G to your configuration. To disable it, set the value to 0.

In addition to the aforementioned query classifier caching, the readwritesplit session command history is enabled by default in 2.3 but is limited to a maximum of 50 commands after which the history is disabled. This is unlikely to show in any metrics but it contributes to the increased memory foorprint of MaxScale.

Unknown Global Parameters

All unknown parameters are now treated as errors. Check your configuration for errors if MaxScale fails to start after upgrading to 2.3.1.

passwd is deprecated

In the configuration file, passwords for monitors and services should be specified using password; the support for the deprecated passwd will be removed in the future. That is, the following

[The-Service]
type=service
passwd=some-service-password
...

[The-Monitor]
type=monitor
passwd=some-monitor-password
...

should be changed to

[The-Service]
type=service
password=some-service-password
...

[The-Monitor]
type=monitor
password=some-monitor-password
...