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Operations Manager–Gateway servers and failover with Powershell dynamic parameters


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 Been thinking about doing a post about failover in SCOM with gateway servers. The idea is that you have several (2 or more) SCOM management servers in your management group. As you start to build your first gateway server, the question about failover/high availability for the gateway comes walking down the street. No problem, powershell comes to the rescue and provides you with a cmdlet you can use – Set-SCOMparentManagementServer.





All nice and dandy, however you can only set the primary management server or the failover server, not both at the same time. In addition you have to provide the cmdlet with gateway and management server objects. You cannot just specify their names. These are by no means huge issues, however I wanted to play around with the dynamic parameter in Powershell and decided to get to work.

Just a fair warning. Dynamic parameters are not pretty in Powershell, however if you put a little effort into the logic, it is quite reasonable to understand. What do we need to create one:
  1. System.Management.Automation.ParameterAttribute object (attributes you decorate with [Parameter] in your functions
  2. System.Collections.ObjectModel.Collection[System.Attribute] (a collection to hold your attributes)
  3. An array of values your parameter accepts
  4. System.Management.Automation.RuntimeDefinedParameter (an object containing the name of the parameter, the type and the attribute collection)
  5. System.Management.Automation.RuntimeDefinedParameterDictionary (a dictionary containing all the parameters; the parameter name and the RuntimeDefinedParameter object)
All of this has to be wrapped in an DynamicParam block. Your function will also need one or all of the BEGIN, PROCESS or END blocks or else your function will not work. I chose to use the BEGIN block.


(BITBUCKET)

 The function needs the OperationsManager module to work since the dynamic parameters are retrieved from the Get-SCOMmanagementServer cmdlet. One big advantage with this dynamic parameter approach is reduced error handling since the parameters will contain objects that exist in the scope we are working in (SCOM).

Furthermore the OperationsManager module is missing a cmdlet. At least I have not found a way to remove a failover server from a gateway configuration. Please note that a Gateway server may have one (1) primary ManagementServer and zero or several failover ManagementServers. Well digging around I found this post by Andreas Zuckerhut where he lays out the foundation for my need to create the missing cmdlet. Be warned, I have tested this in several environments, however use this at your own risk.
Here is your Remove-SCOMGatewayFailover function also with dynamic parameters:

 (BITBUCKET)

Cheers
Tore
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