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15.6.4.8. Creating a Custom Data Collection Item

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15.6.4.8.1. Creating and Using a Custom Data Item XML File

Section 15.6.4.7, “Creating a New Rule: An Example” shows how to create a custom rule and Data Collection Items shows the data items that can be used in rule creation. However, in some circumstances you may want to create a rule that uses a custom data collection item.

This section describes how to create a custom data collection item. The steps are as follows:

  1. Create an XML file to define how the data is collected.

  2. Point the agent configuration file to this XML file.

  3. Restart the agent.

15.6.4.8.1. Creating and Using a 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. The format and content of the XML file that defines the data to be collected is as follows: 

<?xml version="1.0" encoding="utf-8"?>
<classes>
  <class>
    <namespace>mysql</namespace>
    <classname>innodb_min_free</classname>
    <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>

The above works in MySQL 5.1.23 and earlier. For MySQL 5.1.24 and later, the information is reported within the data_Free column, and would need to be declared as: 

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

Save this file as:

  • Windows – C:\Program Files\MySQL\Enterprise\Agent\share\mysql-proxy\items\innodb_min_free.xml

  • Unix – /opt/mysql/enterprise/agent/share/mysql-proxy/items/innodb_min_free.xml

  • Mac OS X – /Applications/mysql/enterprise/agent/share/mysql-proxy/items/innodb_min_free.xml

After saving this file, you must point your mysql-monitor-agent.ini file to it. ( For the location of this file on your operating system see Section 15.3.3.6.1, “MySQL Enterprise Monitor Agent (mysql-monitor-agent.ini) Configuration”.) Find the [mysql-proxy] section and add the file name innodb_min_free.xml to the item-files parameter using a semi-colon as a separator. For example: 

[mysql-proxy]
 ...
item-files = items-mysql-monitor.xml,innodb_min_free.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.