After MariaDB is installed, use the INSTALL PLUGIN command (as the root user) to install the HandlerSocket plugin. This command only needs to be run once, like so:

INSTALL PLUGIN handlersocket SONAME 'handlersocket.so';

After installing the plugin, SHOW PROCESSLIST you first need to configure some settings. All HandlerSocket configuration options are placed in the [mysqld] section of your my.cnf file.

At least the handlersocket_address, handlersocket_port and handlersocket_port_wr options need to be set. For example:

handlersocket_address="127.0.0.1"
handlersocket_port="9998"
handlersocket_port_wr="9999"

After updating the configuration options, restart MariaDB.

On the client side, to make use of the plugin you will need to install the appropriate client library (i.e. libhsclient for C++ applications and perl-Net-HandlerSocket for perl applications).