Customizable processing logic

Customizable processing logic implements rules to customize attribute values for four different data points that are found in an inventory file:

Snow Inventory Server implements hard-coded normalization rules. When processing inventory data, Snow Inventory Server will first apply its hardcoded rules, and, if no normalization can be performed, and then use Customizable processing logic, if a valid DataProcessorRules.xml file is found.

If inventoried data does not match any rules, a default value or a null value will be entered in the Snow Inventory database.

The DataProcessor.xml file structure:

<?xml version="1.0" encoding="utf-8"?>
<DataProcessingTypes>
  <!-- RuleType: all the rules for a given data point are grouped here -->
    <!-- Rule: a rule is defined by an Expression filter and the Output Parameter(s) -->
      <!-- Named Expression Token: represents the Input Parameter, the Name attribute is referred to in the rule's Expression filter -->pattern to match<!-- /Named Expression Token -->
      <!-- Other named tokens ... -->
    <!-- /Rule -->
    <!-- Other rules ... -->
  <!-- /RuleType -->
  <!-- Other rule types... -->
</DataProcessingTypes><?xml version="1.0" encoding="utf-8"?>
<DataProcessingTypes>
  <!-- here are the rules: see examples below -->
</DataProcessingTypes>

For example, a Customizable processing logic file that contains rules to identify an Ubuntu operating system as a Linux-type, server-class, operating-system looks like this:

<?xml version="1.0" encoding="utf-8"?>
<DataProcessingTypes>
  <ServerOperatingSystems>
    <ServerOperatingSystemType Expression="{A}">
      <OperatingSystem Name="A">ubuntu</OperatingSystem>
    </ServerOperatingSystemType>
  </ServerOperatingSystems>
  <OperatingSystemTypes>
    <OperatingSystemType Expression="{A}" OSType="Linux">
      <OperatingSystem Name="A">ubuntu</OperatingSystem>
    </OperatingSystemType>
  </OperatingSystemTypes>
</DataProcessingTypes>

Rules are grouped by RuleType. There are four RuleTypes to reflect the four data points that are handled by Customizable processing logic:

The next section details the RuleTypes, including their input and output parameters.

Expression contains a template for a Boolean expression that must be applied to Named Expression Tokens that are defined in the sub-elements of a rule. The expression is a combination of Boolean logical operators (AND, OR, and NOT) that compare results of logical evaluation of sub-elements. Parentheses can be be used to group different logic operations in an Expression. The Output Parameters that are defined in a rule will be returned if the rule is triggered.

A Named Expression Token represents the Input Parameter of a rule and the value of the Name attribute is referred to in the expression. The logic always matches a value string from an attribute in an inv3x.xml file against the value that is enclosed in its tag. The evaluation compares the value of the Input Parameter that is retrieved from the inv3x.xml file with the string that is enclosed in the parameter. By default, the evaluation contains the "ContainsIgnoreCase" logic. This behavior can be changed by specifying a different logic as value for the Logic attribute of the Named Expression Token. The values for the Logic attribute are:

<Manufacturer Name="B" Logic="StartsWithIgnoreCase">Google</Manufacturer>

Customizable processing logic does not generate logs by default. To facilitate troubleshooting of rules, enable log generation for Customizable processing logic in the Inventory Server snowserver.config file.

[...]
<Logging>
  <Tags>
      [...]
      <Tag>data-rules-engine</Tag>
      [...]
  </Tags>
  [...]
</Logging>
[...]

When data-rules-engine is enabled, logs are generated.

2020-06-02T14:26:33+02:00;data-rules-engine;OperatingSystemType;;;DPRE returned "Windows" as OS type when "OperatingSystem: Microsoft Windows Server 2016 Datacenter, Model: , Manufacturer: , ClientType: Snow Agent - Windows, HypervisorName: , ScannerVersion: , IsMobileDevice: False, IsExternalProvider: False"
2020-06-02T14:27:24+02:00;data-rules-engine;VirtualMachineType;;;DPRE evaluation results "OperatingSystem: Microsoft Windows Server 2016 Datacenter, Model: Google Compute Engine, Manufacturer: Google, ClientType: Snow Agent - Windows, HypervisorName: Google Compute Engine, IsVirtual: True" for client id  "1"