Richard Siddaway's Blog

One of the great things about work flows is that you can stop and start them. A workflow can be stopped, on a temporary basis, by using the Suspend-Workflow activity.

workflow suspend1 {
Get-Service

Suspend-Workflow

Get-Process

}
suspend1

 

This will run the Get-Service activity – and produce output to the console. The workflow will suspend and automatically create a job. You will see output like this:

HasMoreData     : True
StatusMessage   :
Location        : localhost
StartParameters : {}
Command         : suspend1
JobStateInfo    : Suspended
Finished        : System.Threading.ManualResetEvent
InstanceId      : bbe0903d-1720-46da-a6dd-e0a927aa9e11
Id              : 8
Name            : Job8
ChildJobs       : {Job9}
PSBeginTime     : 30/06/2014 19:40:29
PSEndTime       : 30/06/2014 19:40:29
PSJobTypeName   : PSWorkflowJob
Output          : {}
Error           : {}
Progress        : {}
Verbose         : {}
Debug           : {}
Warning         : {}
State           : Suspended

 

Notice the state.

You can  manage the job with the standard job cmdlets

£> Get-Job

Id Name PSJobTypeName State     HasMoreData Location  Command
-- ---- ------------- -----     ----------- --------  -------
8  Job8 PSWorkflowJob Suspended True        localhost suspend1

 

The job is restarted using Resume-Job. Once the job has finished you can use Receive-Job to get the rest of the data.

In my last post I questioned why commands from CDXML didn’t fail as thee weren’t any activities defined for them.  Turns out that functions and other commands that don't explicitly have their own workflow activities are implicitly wrapped in the inline script activity.  As CDXML modules effectively create a function – that means that workflows accept them and run.

Thanks to Steve Murawski for the answer.

Last time we saw that you’re not really using cmdlets in PowerShell workflows – you’re using workflow activities. Some cmdlets haven’t been packaged into activities and for those you need to put them in an Inlinescript block.  You can also use an Inlinescript block to run any arbitrary piece of PowerShell.

One thing I hadn’t tried was using some of the CDXML (WMI class wrapped in XML and published as a PowerShell module) modules that ship in Windows 8 and later. As far as I was aware they hadn’t been packaged as activities -

so thought I’d try this

workflow net1 {
parallel {
  Get-NetAdapter
  Get-NetIPAddress
}
}
net1

 

Surprisingly it worked.

The only reason I can think of that it works is that the way CDXML publishes the cmdlets as functions -  ls function:\Get-NetAdapter | fl *

Enables a workflow to use the function. Even if the module containing the cmdlet hasn’t been explicitly or implicitly loaded the workflow still runs.

You can tell these cmdlets haven’t been packaged as activities as the activity common parameters aren’t available on them.

One of life’s little mysteries. I’ll get to the bottom of it and find out why eventually. In the meantime our workflows just became a whole lot richer in terms of functionality.

This is a simple function to return some data about a system:

function get-serverdata {

Get-CimInstance -ClassName Win32_OperatingSystem

Get-Service

Get-Process

}

get-serverdata

 

The function will return the CIM data about the operating system, then the service data and then the process data. The only difference to running the cmdlets interactively is that the display for services and processes defaults to a list rather than a table.

Status      : Stopped
Name        : WwanSvc
DisplayName : WWAN AutoConfig

Id      : 1524
Handles : 81
CPU     : 0.015625
Name    : armsvc

 

Now lets try that as a workflow:

 

workflow get-serverdata {

Get-CimInstance -ClassName Win32_OperatingSystem

Get-Service

Get-Process

}

get-serverdata

 

You’ll see the data returned in exactly the same order – operating system, services and processses. The only difference is that a PSComputerName property is added to the output.

Status         : Stopped
Name           : WwanSvc
DisplayName    : WWAN AutoConfig
PSComputerName : localhost

Id             : 1524
Handles        : 81
CPU            : 0.015625
Name           : armsvc
PSComputerName : localhost

 

I didn’t emphasis this when discussing parallel and sequential processing earlier but the default action for a workflow is to process the commands sequentially. You use the parallel and sequence keywords to control that processing – for instance to run the cmdlets in parallel:

workflow get-serverdata {

parallel {
Get-CimInstance -ClassName Win32_OperatingSystem

Get-Service

Get-Process
}

}

get-serverdata

 

From this I see a block of service data (in table format) followed by the first process, another service, the CIM data and more services then mixed services and process data until then end.

I can’t emphasise this point enough – when running workflow tasks in parallel you have no control of the order in which data is returned.

 

You may be tempted to try something like this:

workflow get-serverdata {

parallel {
Get-CimInstance -ClassName Win32_OperatingSystem

Get-Service | Format-Table

Get-Process | Format-Table
}

}

get-serverdata

 

Don’t. You see an error message:

At line:6 char:15
+ Get-Service | Format-Table
+               ~~~~~~~~~~~~
Cannot call the 'Format-Table' command. Other commands from this module have been packaged as workflow activities, but this command was specifically excluded. This is likely because the command requires an interactive Windows PowerShell session, or has behavior not suited for workflows. To run this command anyway, place it within an inline-script (InlineScript { Format-Table }) where it will be invoked in isolation.
    + CategoryInfo          : ParserError: (:) [], ParseException
    + FullyQualifiedErrorId : CommandActivityExcluded

 

There are a couple of very important pieces of information in this message:

“packaged as workflow activities”

The commands used in the workflows in this post ARE NOT CMDLETS. I’ve capitalised that to emphasis. Workflows do not run PowerShell cmdlets – they use workflow activities. These are cmdlets repackaged to run in workflows. Not all cmdlets have bee repackaged as activities and not all cmdlets can be which leads to the second important point from the error.

“To run this command anyway, place it within an inline-script (InlineScript { Format-Table }) where it will be invoked in isolation. “

 

Any cmdlet or command that hasn’t been specifically converted to a workflow activity can be wrapped in an inlinescript block if you need to run it in a workflow. The example would become:

workflow get-serverdata {

parallel {
Get-CimInstance -ClassName Win32_OperatingSystem

inlinescript {
Get-Service | Format-Table

Get-Process | Format-Table
}

}

}

get-serverdata

 

You can see a list of the cmdlets that have not been implemented as workflow activities in the this link http://technet.microsoft.com/en-us/library/jj574194.aspx

Scroll down to excluded cmdlets.

 

PowerShell workflows look like PowerShell but they are not PowerShell. Next time we’ll dig a bit further under the covers of PowerShell workflows.

I said in the first post in this series that you could force a workflow to perform tasks in parallel or in sequence. Starting with parallel you can force parallel execution by using the parallel keyword:

workflow thursday1 {
parallel {
   1..26 | foreach {$psitem}
   65..90 | foreach {[char][byte]$psitem}
   97..122 | foreach {[char][byte]$psitem}

   1..26 | foreach {$psitem}
   65..90 | foreach {[char][byte]$psitem}
   97..122 | foreach {[char][byte]$psitem}

   1..26 | foreach {$psitem}
   65..90 | foreach {[char][byte]$psitem}
   97..122 | foreach {[char][byte]$psitem}
}
}

thursday1

In this workflow I’m printing out the numbers 1-12, the characters A-Z and a-z then repeating those actions another 2 times. The repetition is to force the parallelism to be visible. If you just run one repetition everything runs so fast that you don’t see any evidence of parallel activity.  if you look carefully at the output you will see evidence of parallelism. For instance the test I ran showed this partial sequence of results:

Y
16
17
B
18
C
19
20
D
a
b

No prizes for guessing that the keyword to force things to run sequential is sequence

workflow thursday2 {
sequence {
   1..26 | foreach {$psitem}
   65..90 | foreach {[char][byte]$psitem}
   97..122 | foreach {[char][byte]$psitem}
}
}

thursday2

No matter how many times you run this you’ll always get the same sequence of results – numbers, upper case then lower case characters.

You can mix and match

workflow thursday3 {
parallel {
    sequence {
     1..26 | foreach {$psitem}
     65..90 | foreach {[char][byte]$psitem}
     97..122 | foreach {[char][byte]$psitem}
   }
    sequence {
     1..26 | foreach {$psitem}
     65..90 | foreach {[char][byte]$psitem}
     97..122 | foreach {[char][byte]$psitem}
   }
    sequence {
     1..26 | foreach {$psitem}
     65..90 | foreach {[char][byte]$psitem}
     97..122 | foreach {[char][byte]$psitem}
   }
}
}

This runs the sequence of numbers, upper and lower case three times in parallel

or

workflow thursday4 {
sequence {
    parallel {
     1..26 | foreach {$psitem}
     65..90 | foreach {[char][byte]$psitem}
     97..122 | foreach {[char][byte]$psitem}
   }
    parallel {
     1..26 | foreach {$psitem}
     65..90 | foreach {[char][byte]$psitem}
     97..122 | foreach {[char][byte]$psitem}
   }
    parallel {
     1..26 | foreach {$psitem}
     65..90 | foreach {[char][byte]$psitem}
     97..122 | foreach {[char][byte]$psitem}
   }
}
}

thursday4

 

which runs numbers, upper and lower case in parallel – three times in sequence

Try thursday3 and thursday4 and observe the results. I’d encourage you to experiment with combinations of sequence and parallel so that you get a feel for the difference between the two types of action.

Your observations should help reinforce the message from the first post – you can’t predict the order of results when performing tasks in parallel.