Parameter replacements (part 3)
To continue Parameter replacements series, let’s remind ourselves that context parameters can be used and will be replaced by the runtime with the actual parameter value. So far I talked about Config and MPElement replacements before and now I will try to describe Target context parameter in this post …
Target Context Parameters
When a monitoring object (rule/monitor/task) is instantiated and executed for a managed entity instance, the monitoring object instance can retrieve its target managed entity specific context as part of the configuration. The following context is available for this monitoring object:
- Any property of the targeted managed entity type including the ones inherited, if the type is derived from a base type.
- Any property of the host type of the target managed entity type. Not only properties of the immediate host can be retrieved, as well as the properties the host of the host can be retrieved if exists.
MP author can access this context using MPTarget context parameter.
Syntax
Use the following syntax to retrieve the managed entity instance id:
Use the following syntax to retrieve the management group id or name of the target managed entity: (Note that every managed entity instance belongs to a management group.)
$Target/ManagementGroup/Id$
$Target/ManagementGroup/Name$
Use the following syntax to retrieve the target managed entity’s properties:
$Target/Property/<PropertyName>$
$Target/Property[Type=”<RelTypeName>”]/<PropertyName>$
$Target/Property[Type=”<MPAlias>!<RelTypeName>”]/<PropertyName>$
Use the following syntax to refer to a property of host of the target managed entity type in the hosting hierarchy
$Target/Host/Property[Type=”<RelTypeName>”]/<PropertyName>$
$Target/Host/Host/Property[Type=”<RelTypeName>”]/<PropertyName>$
Usage Note:
When a property name is referred as a target parameter, the property name has to be fully qualified. MPAlias needs to be pre-appended to the type name, if the type is not defined in the same MP where the target properties are referred. RelTypeName defines first non-abstract base class which defines property identified by PropertyName.
Example:
<Discovery ID="Sample" Target="Windows!Microsoft.Windows.Computer">
<Category>Discovery</Category>
<DiscoveryTypes />
<DataSource ID="DS" TypeID="Windows!Microsoft.Windows.TimedScript.DiscoveryProvider">
<IntervalSeconds>900</IntervalSeconds>
<SyncTime />
<ScriptName>sampleDiscovery.vbs</ScriptName>
<Arguments>$MPElement$ $Target/Id$</Arguments>
<ScriptBody><![CDATA[
Option Explicit
Dim oArgs
Set oArgs = WScript.Arguments
Dim SourceId, ManagedEntityId
SourceId = oArgs(0)
ManagedEntityId = oArgs(1)
Dim oApi
Set oApi = CreateObject("MOM.ScriptAPI")
Dim oData
Set oData = oApi.CreateDiscoveryData ( _
0, _
SourceId, _
ManagedEntityId _
) …
<Rule ID=" AlertFromEvent111" Target="Windows!Microsoft.Windows.Computer">
<Category>AvailabilityHealth</Category>
<DataSources>
<DataSource ID="DS" TypeID="Windows!Microsoft.Windows.EventProvider">
<ComputerName>$Target/Property[Type="Windows!Microsoft.Windows.Computer"]/NetworkName$</ComputerName>
<LogName>Application</LogName>
<Expression>
<SimpleExpression>
<ValueExpression>
<XPathQuery>EventDisplayNumber</XPathQuery>
</ValueExpression>
<Operator>Equal</Operator>
<ValueExpression>
<Value>111</Value>
</ValueExpression>
</Expression>
</DataSource>
</DataSources>
<WriteActions>
<WriteAction ID="GenerateAlert" TypeID="SystemHealth!System.Health.GenerateAlert">
<Priority>2</Priority>
<Severity>1</Severity>
<AlertMessageId>$MPElement[Name=" AlertFromEvent111.Message"]$</AlertMessageId>
<AlertParameters>
<AlertParameter1>$Target/Property[Type="Windows!Microsoft.Windows.Computer"]/PrincipalName$</AlertParameter1>
<AlertParameter2>$Data/EventDisplayNumber$</AlertParameter2>
</AlertParameters>
<Suppression>
<SuppressionValue/>
</Suppression>
</WriteAction>
</WriteActions>
</Rule>
Note:
Similarly to MPElement replacement, use of the Target context parameter may be hidden by use of our authoring tools as well. There is also some documentation within MSDN (OpsMgr scripting, Using Context Parameters in script, …) describing its use for OpsMgr scripting.
Also, please check back again, I will talk about last context parameter ($Data) which is probably most cryptic of all in my next post …
