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15.7.5 Creating a Custom Data Collection Item »
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15.7.4.7. Creating a New Rule: An Example

This section documents the steps required to create a rule. Before attempting to create a rule, please review the preceding sections of this chapter.

This example creates a rule that checks the number of rows in a table. Having 50,000 rows in this table is deemed to warrant a critical alert. Lesser numbers are assigned to informational and warning level alerts.

Begin by navigating to the Advisors tab and clicking the manage rules link. Then choose the create rule button.

Create your custom rule by following these steps:

  1. Using the Rule Name text box, give the rule an appropriate name. Something such as "Excessive number of records in table_name table", may be appropriate.

  2. From the Advisor drop down list box choose an advisor group for your rule. The Administration group of rules might be suitable but if you wish, create your own group of advisors. For instructions on doing this see Section 15.7.4.1, “Creating Advisors”.

  3. Enter the following expression in the Expression text area: '%table_name_num_rows% > THRESHOLD'. Replace table_name with the name of the table you wish to monitor. Note that the variable %table_name_num_rows% has not yet been defined.

  4. Set the Thresholds.

    1. Set the Critical Alert level to 50000.

    2. Set the Warning Alert level to 10000.

    3. Set the Info Alert level to 5000.

  5. Define your variable in the Variable Assignment frame.

    1. In the Variable text box enter '%table_name_num_rows%, the variable used in the Expression text box

    2. In the Data Item drop down list box find and select the mysql:table:numrows entry. (For a description of all the data items available see Data Collection Items.)

    3. In the Instance text box enter database_name.table_name.

  6. Add appropriate entries for the Problem Description, the Advice, and the Links text areas. If you wish, use Wiki markup for these text areas. See Section 15.7.4.6, “Wiki Format” for more information. Note that you can also reference the '%table_name_num_rows% variable in these text areas. For example, you can display the current number of rows with a message such as 'table_name currently has %table_name_num_rows% rows.'

  7. Save the rule.

Once the rule is created it needs to be scheduled against the server that contains the database table you wish to monitor. For instructions on scheduling rules see Section 15.7.2, “Scheduling Rules”.