An introduction to developing PowerShell workflows. Explains concepts, terminology and recommended practices.

1. Intro to
PowerShell
Workflow
JEFF HICKS

2. Agenda
What is Workflow?
Workflow Syntax
Running Workflows
Practical Workflows
Best Practices

3. Think!
Just because you can use a PowerShell
workflow doesn’t mean you should.

4. Definitions – What is a
Workflow
A robust multi-machine orchestration
engine
Designed for long running unattended tasks
across potentially thousands of machines
Persistent states can survive reboots and
network interruptions
Previously built in Visual Studio

5. Definitions - What is
PowerShell Workflow?
• Persistence via check points
• Suspend and Resume capabilitiesRobust
• Parallel tasks
• Connection pooling
• Connection throttling
Performance
and
Scalability
• Use existing cmdlets*
• No need to master XAML or use Visual Studio
• Built in parameters for multi-machine management
PowerShell
Based

6. Workflow Scenarios
Server deployment
Server configuration/remediation
User provisioning
Private cloud deployments
Sharepoint configuration
Any business workflow that can be orchestrated with command line tools.

7. Key Workflow Concepts
Workflow is a series of orchestrated activities
Workflow activities are isolated
All data and objects are serialized
Objects are strongly typed
Workflows use static scoping

8. Requirements
Built on .NET Framework 4.0 and
Windows Workflow Foundation
Requires PowerShell 3.0
Requires PowerShell 3.0 remoting
Leverages PowerShell's job
infrastructure

9. Requirements: Remoting
Workflows connect to machines using WSMan protocol
Connects to the default Workflow session configuration
PS C:> get-pssessionconfiguration
microsoft.powerShell.workflow
Important defaults:
◦ Max persistence storage 10GB
◦ Max memory per shell 1GB
◦ Admin permissions required
Be very careful of changing this configuration

10. High Level
Workflow Configure-Server
{
#magic happens
}
PS C:> configure-server –pscomputername SRV01
Script
converted to
Workflow
XAML
Workflow
endpoint
Workflow
engine

11. Limitations and Gotchas
All objects
and data
must be
"serializable"
Must use full
cmdlet and
parameter
names –
these are
activities
No
positional
parameters
No Begin/
Process/End
scriptblocks
No
"eventing"

12. Limitations and Gotchas
No Traps -
Use
Try/Catch
Not intended
to be
interactive –
don’t use
Write-Host.
No comment
based help -
must use
MAML
formatted
files
Pay close
attention to
scope!

13. Workflow Architecture
Workflow Engine
PowerShell Client
Session
PowerShell
Workflow
“Service”
WinRM Client
Client
PSRP/PowerShell
Managed Node
Remoting
Commands/API
Operation Host Process
Operations
Host
WSMan/CIM
Managed Node

14. Building Workflows
Don't
simply
replace
"Function"
with
"Workflow"
Start new
and plan
out your
activities
Minimize
sharing of
data or
variables
across
activities
PowerShell
turns your
workflow
into XAML
Workflow is
a new
command
type in
PowerShell
3.0
PS C:> get-command -commandtype Workflow

15. Syntax: Sequence
Execute a collection of activities in order
Can be executed with Parallel
Watch out for scope!

16. Syntax: Sequence
Sequence {
MyCommand1
}
Sequence {
MyCommand2
MyCommand3
MyCommand4
}
This command runs
Then these commands run in sequence

17. Syntax: Parallel
Execute a collection of activities independently and in parallel
ForEach -Parallel
• The parameter only works in a workflow
• Run a set of commands in parallel for each object in a collection
Parallel key word
• Run a set of commands simultaneously and in parallel
• Runs in a new scope
• Often used to run a series of Sequences

18. Parallel
Parallel {
MyCommand1
MyCommand2
MyCommand3
Sequence {
MyCommand4
MyCommand5
} #sequence
} #parallel
These commands run in
sequence
Commands and
sequence run
simultaneously

19. ForEach -Parallel
ForEach -parallel ($item in $object) {
#do something with each object
MyCommand1 $item
MyCommand2 $item
}
For each item in the
collection…
Run these commands
All object processed
simultaneously

20. Syntax: InlineScript
Send PowerShell commands to remote machine(s)
Runs out-of-process
Runtime command validation
This is really a series of Invoke-Command activities
Use for all other non-activity commands

21. InlineScript
Workflow New-Audit {
Inlinescript {
$procs = Get-WmiObject Win32_process
$procs | Select-Object ProcessID,Name,
@{Name="RunTime";Expression={(Get-Date) -
$_.ConvertToDateTime($_.CreationDate)}},
@{Name="Owner";Expression={"$($_.GetOwner().Doma
in)$($_.GetOwner().User)"}}}
}

22. Syntax: Scope and Variables
Workflows uses static scopes, i.e. PowerShell won't
"search" for a variable
Assume each activity is isolated
Can use $Workflow:MyVar for “global” references
• Read-only
• Available from InlineScript
Access "out of scope" variables with $Using:MyVar

23. Syntax: Common Parameters
All workflows
have a set of
common
parameters They do not need
to be defined
•PSComputerName
•PSCredential
•PSConnectionRetryCo
unt
•PSActionRetryCount
•PSPersist

24. Syntax: Persistence
Workflows can be
made persistent to
survive interruptions
Planned reboots
Network interruptions
By default entire
workflow restarts
unless…
Set persistence per
activity
•Checkpoint-Workflow
•Persist
•Suspend-Workflow
Set persistence for
the entire workflow
-PSPersist common
parameter
Set to $True:
-pspersist $true

25. Running Workflows
Load
workflow
Specify
remote
computers
Specify
credentials
Run as a
job
Use a
Workflow
session

26. Invoke-AsWorkflow
Run any command or expression as a workflow
Run as an InlineScript
Executed from the console
Great for ad-hoc remote management without writing a workflow
Invoke-AsWorkflow -CommandName get-eventlog -
Parameter @{Logname="System";Newest=10;
Entrytype="Error"} -pscomputername $computers -asjob

27. Workflow Sessions
Run Workflows from within a special PSSession
Workflows can be monitored and managed from within the session
Great for long running workflows or those that might be suspended and
resumed
Session can be disconnected and reconnected

28. Best Practices
Try to test locally and interactively
Use Write-Verbose for tracing and troubleshooting
Use a workflow-aware editor like the PowerShell ISE
Take advantage of parallelism
Plan your activities…this is not just another way to script

29. Resources
The Lonely Administrator (http://jdhitsolutions.com/blog)
PowerShell in Depth
http://PowerShell.org
http://blogs.technet.com/b/heyscriptingguy

30. Thank You
http://jdhitsolutions.com/blog
jhicks@jdhitsolutions.com
@JeffHicks
http://plus.google.com/+JefferyHicks