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6.6 Disabling and Unscheduling Rules »
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6.5.1. 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. A sample entry is provided in the custom.xml file that is included during installation. You can replace, or add the following definition to the file: 

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

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

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

For this change to take effect you must restart the agent. To do this see:

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