Guidelines for Creating Additional Filters for Node Groups

The Additional Filters Editor enables you to create expressions to further define the nodes to be included in a Node Group. Make sure to design any complex Additional Filters offline as a Boolean expression first. This method can help to minimize errors when entering your expressions using the Additional Filters Editor.

When creating Additional Filters for a Node Group, note the following:

• NNMi treats each set of expressions associated with a Boolean Operator as if it were enclosed in parentheses and evaluated together rather than in order of grouping as the nesting implies. Therefore, when using the AND operator to combine expressions that include Custom Attributes, include only one customAttrName/customAttrValue pair in the expression. Otherwise, if you use multiple customAttrName and customAttrValue pairs with the AND operator, the results might not be as expected. Click here for an example.

  In the following example, because the AND Boolean operator indicates that NNMi should evaluate all of the customAttrname and customAttrvalue pairs together, it is not possible for any nodes to match this Additional Filters expression:

  Additional Filter Expression Example 1:

  ((customAttrName = capability) AND (customAttrValue = com.hp.nnm.capability.card.fru)) AND ((customAttrName = location) AND (customAttrValue = datacenter1))

  This is because customAttrName would need to match both capability and>location at the same time. However, if you use the OR operator to combine the customAttrName and customAttrValue pairs as shown in the following example, the filter should work as expected.

  Additional Filter Expression Example 2:

  ((customAttrName = capability) AND (customAttrValue = com.hp.nnm.capability.card.fru)) OR ((customAttrName = location) AND (customAttrValue = datacenter1))

  Using the Node values listed in the following table, all three nodes (nodeA, nodeB, and nodeC) pass the filter in Example 2 because each of these nodes has either the value com.hp.nnm.capability.card.fru for capabilityor the value datacenter1 for location.

  Example Data

  Node Name	capabilty	customAttrName	customAttrValuee
  nodeA	com.hp.nnm.capability.card.fru	location	datacenter1
  nodeB	com.hp.nnm.capability.card.fru	<undefined>	<undefined>
  nodeC	<undefined>	location	datacenter1

• Use the EXISTS and NOT EXISTS operators when you want NNMi to consider nodes that either do or do not have any Capabilities or Custom Attributes when evaluating the Filter String. See Specify Node Group Additional Filters for more information.
• View the expression displayed under Filter String to see the logic of the expression as it is created.

• The AND and OR Boolean Operators must contain at least two expressions as shown in the example below.

  AND 

       sysName like cisco*

       sysName != cisco2811

       OR

             sysLocation = Boston

             sysContact In (Johnson,Hickman)

  NNMi evaluates the expression above as follows:

  sysName like cisco* AND sysName != cisco2811 AND (sysLocation = Boston OR sysContact in (Johnson, Hickman))

  • NNMi finds all nodes with a (system name) sysName beginning with cisco, except not cisco2811.
  • Of these nodes, NNMi then finds all nodes with a (system location) sysLocation of Boston or (system contact name) sysContact of Johnson or Hickman.
• NNMi evaluates only those nodes that contain values for all of the attributes included in the Additional Filter expression. Click here for an example.

  If your Node Group filter expression includes the capability and customAttrName attributes, then NNMi evaluates only nodes that have a value defined for both capability and customAttrName. For example, if you create a Node Group using the following Additional Filters expression, then NNMi evaluates only those nodes that have a value defined for capability and a value defined for customAttrName:

  (capability = com.hp.nnm.capability.card.fru) OR (customAttrName = location)

  Using the Node values listed in the following table, NNMi only evaluates nodeA. This is because nodeA contains a value for capability and a value for customAttrName. NNMi does not evaluate nodeB because it does not have a value for customAttrName. NNMi does not evaluate nodeC because it does not have a value for capability. NodeA also passes Node Group Additional Filter because its capability value of com.hp.nnm.capability.card.fru matches the value specified in the Additional Filter expression. Therefore, only nodeA is included in this example Node Group.

  Example Data

  Node Name	capabilty	customAttrName	customAttrValuee
  nodeA	com.hp.nnm.capability.card.fru	location	datacenter1
  nodeB	com.hp.nnm.capability.card.fru	<undefined>	<undefined>
  nodeC	<undefined>	location	datacenter1

  Tip You can populate a placeholder value, such as "none" or "undefined" for any attribute that you want to use in an Additional Filter.

• The placement of your cursor and the subsequent text that is selected is important when performing operations using the Additional Filters Editor. For example, you append to or replace, the expression that is selected.
• The placement of your cursor and the subsequent text that is selected is especially important when adding your Boolean operators. See Add Boolean Operators in the Additional Filters Editor for more information.

• You can drag any of the following items to a new location in the Filter String:

  • Filter Editor Options: AND, OR, NOT, EXISTS, NOT EXISTS
  • Filter Expression (Attribute, Operator and Value)

• When moving items in the Filter String, note the following:

  • Click the item you want to move before dragging it to a new location.
  • As you drag a selected item, an underline indicates the target location.
  • If you are moving the selection up, NNMi places the item above the target location.
  • If you are moving the selection down, NNMi places the item below the target location.
  • If you attempt to move the selection to an invalid target location, NNMi displays an error message.