Modifying the Custom Data Item XML File

As an example, this section shows how to create a data item for monitoring the amount of free InnoDB tablespace. You can have multiple items in your custom.xml file, just specify additional class entries. The custom.xml file in the installation includes a sample entry. You can replace that entry, or add the following definition to the file:

<?xml version="1.0" encoding="utf-8"?>
    <query><![CDATA[SELECT MIN(substring_index(substring_index(table_comment," ",3)," ",-1)/1024/1024)
      as Free FROM INFORMATION_SCHEMA.TABLES WHERE engine = 'InnoDB']]></query>

After saving the file, ensure that the agent-item-files parameter within the configuration includes the custom.xml file. For example:

agent-item-files = share/mysql-monitor-agent/items/quan.lua,share/mysql-monitor-agent/items/items-mysql-monitor.xml, share/mysql-monitor-agent/items/agent-allocation-stats.lua,share/mysql-monitor-agent/items/custom.xml

Restart the agent to put this change into effect. To do this, see:

Once the agent has restarted, the new data item is in the Data Item drop down list box on the Rule Definition page. Its fully qualified name is mysql:innodb_min_free:Free.