Specifying cross-node dependencies

Applies To: Windows PowerShell 5.0

DSC provides special resources, WaitForAll, WaitForAny, and WaitForSome that can be used in configurations to specify dependencies on configurations on other nodes. The behavior of these resources is as follows:

  • WaitForAll: Succeeds if the specified resource is in the desired state on all target nodes defined in the NodeName property.
  • WaitForAny: Succeeds if the specified resource is in the desired state on at least one of the target nodes defined in the NodeName property.
  • WaitForSome: Specifies a NodeCount property in addition to a NodeName property. The resource succeeds if the resource is in the desired state on a minimum number of nodes (specified by NodeCount) defined by the NodeName property.

Syntax

The WaitForAll and WaitForAny resources share the same syntax. Replace <ResourceType> in the example below with either WaitForAny or WaitForAll. Like the DependsOn keyword, you will need to format the name as "[ResourceType]ResourceName". If the resource belongs to a separate Configuration, include the ConfigurationName in the formatted string "[ResourceType]ResourceName::[ConfigurationName]::[ConfigurationName]". The NodeName is the computer, or Node, on which the current resource should wait.

<ResourceType> [string] #ResourceName
{
    ResourceName = [string]
    NodeName = [string]
    [ DependsOn = [string[]] ]
    [ PsDscRunAsCredential = [PSCredential]]
    [ RetryCount = [Uint32] ]
    [ RetryIntervalSec = [Uint64] ]
    [ ThrottleLimit = [Uint32]]
}

The WaitForSome resource has a similar syntax to the example above, but adds the NodeCount key. The NodeCount indicates how many Nodes the current resource should wait on.

WaitForSome [String] #ResourceName
{
    NodeCount = [UInt32]
    NodeName = [string[]]
    ResourceName = [string]
    [DependsOn = [string[]]]
    [PsDscRunAsCredential = [PSCredential]]
    [RetryCount = [UInt32]]
    [RetryIntervalSec = [UInt64]]
    [ThrottleLimit = [UInt32]]
}

All WaitForXXXX share the following syntax keys.

| Property | Description | | RetryIntervalSec| The number of seconds before retrying. Minimum is 1.| | RetryCount| The maximum number of times to retry.| | ThrottleLimit| Number of machines to connect simultaneously. Default is New-CimSession default.| | DependsOn | Indicates that the configuration of another resource must run before this resource is configured. For more information, see DependsOn| | PsDscRunAsCredential | See Using DSC with User Credentials |

Using WaitForXXXX resources

Each WaitForXXXX resource waits for the specified resources to complete on the specified Node. Other resources in the same Configuration can then depend on the WaitForXXXX resource using the DependsOn key.

For example, in the following configuration, the target node is waiting for the xADDomain resource to finish on the MyDC node with maximum number of 30 retries, at 15-second intervals, before the target node can join the domain.

Configuration JoinDomain
{
    Import-DscResource -Module xComputerManagement, xActiveDirectory

    Node myDC
    {
        WindowsFeature InstallAD
        {
            Ensure = 'Present'
            Name = 'AD-Domain-Services'
        }

        xADDomain NewDomain
        {
            DomainName = 'Contoso.com'
            DomainAdministratorCredential = (Get-Credential)
            SafemodeAdministratorPassword = (Get-Credential)
            DatabasePath = "C:\Windows\NTDS"
            LogPath = "C:\Windows\NTDS"
            SysvolPath = "C:\Windows\Sysvol"
        }
    }

    Node myDomainJoinedServer
    {
        WaitForAll DC
        {
            ResourceName      = '[xADDomain]NewDomain'
            NodeName          = 'MyDC'
            RetryIntervalSec  = 15
            RetryCount        = 30
        }

        xComputer JoinDomain
        {
            Name             = 'myPC'
            DomainName       = 'Contoso.com'
            Credential       = (Get-Credential)
            DependsOn        ='[WaitForAll]DC'
        }
    }
}

When you compile the Configuration, two ".mof" files are generated. Apply both ".mof" files to the target Nodes using the Start-DSCConfiguration cmdlet

Note: By default the WaitForXXX resources try one time and then fail. Although it is not required, you will typically want to specify a RetryCount and RetryIntervalSec.

See Also