@JohnKoepi backend system engineer

Approach into strong typed configuration management DSL with FAKE, F#, WinRM and PowerShell

PowerShell is a dynamic language based on a subset of C# with extension into the shell requirements. This language is the future of Windows based servers administration and management.

Almost all popular Configuration Management Systems came from Linux world like Puppet, Ansible, Salt, Chef, CF-engine etc are weakly typed, based either on specific DSL or implementation Language. There is not much in the Windows world. Microsoft always tend to provide their own vendor locking solution and this time its not an exception: Desired State Configuration system based on PowerShell.

Yet all those solutions struggles all the problems all dynamic languages have. This means, that after making a change you can't be sure, if it is valid, will it interpret or execute until you give 100% test coverage. PowerShell in addition do not have static code analysis tools and do not protect from errors like using undefined variables (or steeled from another scopes).

This leads to the problems of correctness, support and maintainability. You can't be sure, until you run it.

In PowerShell case Pester can help providing TTD infrastructure like running framework, context, dsl, mocking, etc.

I am sure this will change. Languages in the latest decade tend to evolve in the direction of complex strong type systems, automatic memory management and functional pureness. Following this logic, the community will see more systems like Propellor or FAKE which tend to provide strong typed DSLs based on underlying platform capabilities.

I was interested in researching of the state of strong typed systems around PowerShell infrastructure from the POV of combining it with Windows Remote Management system, which is popular in our practice and invaluable in whole current Microsoft server strategy.

This is an overview of the method of combining PowerShell, Windows Remote Manager F# and FAKE.

Possible implementations of the Configuration Management System could be based on following concepts:

  • Given FSharp runtime, compiler and required libraries on every Target machine, system will pass F# scripts inside ScriptBlocks as a simple text, compile them remotely and execute directly via dynamic type resolving, interface cast and execution.

    • CodeDom in memory on demand compilation
    • Direct fsc.exe call
    • FSharp.Compiler.Services ?
  • The system can compile locally on demand F# scripts, pass compiled assemblies any how to the target machine (via pssession, cloud storage, etc) and run them remotely.

    • fsc.exe, copy to remote site
    • direct injection of the assembly into pssession from []byte, instead of distribution

Personally, I would prefer to have the system which supports all modes of operations:

  • Pass F# scripts as text via Invoke-Command / PSSession and executing and compiling them dynamically remotely on demand via existing remote infrastructure.
  • To be able to execute locally compiled and prepared scripts batches to the remote site in the case of the preference. (omitting compilation should faster process at least)

7 Configuration Management (CM) Tools You Need to Know About

FAKE - F# Make is a build automation system with capabilities which are similar to make and rake. It is using an easy domain-specific language (DSL) so that you can start using it without learning F. Combination of FAKE capabilities, DSL and PowerShell remoting looks interesting combination.

Prepare FSharp compiler environment

During this process, I have met enormous amount of unstable effects and exceptions amount Windows tooling and services which I intended not to resolve into the sake of saving my time.

Use the following requirements and installation steps:

  1. Requires .NET 4.5:
    • On Windows 10 .NET 4.6 is already present by default
    • On Windows 8 and Windows 2012 Server, this is already present by default
    • On Windows 7 and Windows 2008 Server, install .NET 4.5 from Microsoft
  2. Requires the Windows SDK:
  3. Requires Microsoft Build Tools 2015 - Install Microsoft Build Tools 2015
  4. Install the free Visual F# Tools 4.0 from Microsoft

Test your PowerShell CLR environment

Check $PSVersionTable.

If its not 4.0, there are two ways to tell PowerShell version 2.0 to utilize .NET Framework 4.

You’ll want to create powershell.exe.config and powershell_ise.exe.config and place them in your $pshome directory.

Here is what you want in both of those .config files:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <startup>
      <supportedRuntime version="v4.0.30319" />
      <supportedRuntime version="v2.0.50727" />
    </startup>
</configuration>

Here is the location of $pshome by default:

  • 32-bit machines: C:\Windows\System32\WindowsPowershell\v1.0
  • 64-bit machines
    • 32-bit version: C:\Windows\SysWOW64\WindowsPowershell\v1.0
    • 64-vit version: C:\Windows\System32\WindowsPowershell\v1.0

or google for PowerShell .NET 4.0. src

Test your WinRM environment

Invoke-Command -ComputerName SECOND -ScriptBlock { Write-Output $env:COMPUTERNAME }

Microsoft Build Tools 2015

I have tried to install from Microsoft Build Tools 2015 with:


Invoke-Command -ComputerName SECOND -ScriptBlock {
    $webclient = New-Object Net.WebClient
    $url = 'https://go.microsoft.com/fwlink/?LinkId=615458'
    $webclient.DownloadFile($url, "$pwd\BuildTools_Full.exe")
    .\BuildTools_Full.exe /Quiet /Full
}

and it did not work for me. Don't know why.

FSharp codedom

Latest version of nuget FSharp.Compiler 4.4.0.0 is not compatible to CodeDom 0.9.4.

If you are using nuget, to install FSharp.Core to the remote site, the 4.3.1.0 will be fine for CodeDom 0.9.4. Nonetheless I have failed to run fsharp compiler from the nuget package due to some magical mscorlib.dll incompatibilities and some others unresolved issues.

If you use nuget to provide a compiler, don't forget to include path the tools directory (with fsc / fsi) into the $env:PATH.


Invoke-Command -ComputerName SECOND -ScriptBlock {
    $webclient = New-Object Net.WebClient
    $url = 'http://download.microsoft.com/download/9/1/2/9122D406-F1E3-4880-A66D-D6C65E8B1545/FSharp_Bundle.exe'
    $webclient.DownloadFile($url, "$pwd\FSharp_Bundle.exe")
    .\FSharp_Bundle.exe /install /quiet
}

This will take some time.

Test CodeDom


Invoke-Command -ComputerName SECOND -ScriptBlock {
    # Cache
    $tools = 'C:\Tools'

    if (-not (Test-Path -Path $tools)) {
        New-Item -Path $tools -ItemType 'directory'
    }

    Set-Location $tools

    # Libs
    @('FSharp.Compiler.CodeDom') | ? {
        -not (Get-ChildItem -Path (Join-Path -Path $tools -ChildPath "$_*"))
    } | % {
        nuget install $_
    }

    # Include
    Add-Type -Path 'C:\Program Files\Reference Assemblies\Microsoft\FSharp\.NETFramework\v4.0\4.3.1.0\FSharp.Core.dll'
    Get-ChildItem -Path C:\Tools\FSharp.Compiler.CodeDom.*\lib\net40\FSharp.Compiler.CodeDom.dll | % { Add-Type -Path $_.FullName }

    # Example of calling -TypeDefinition
    $fibCode = '
        module Fibonacci
        let fibs =
            (1,1) |> Seq.unfold
                (fun (n0,n1) ->
                    Some(n0, (n1, n0 + n1)))
        let get n =
            Seq.item n fibs
    '

    # Compile
    $FSharpCodeProvider = New-Object FSharp.Compiler.CodeDom.FSharpCodeProvider
    Add-Type -TypeDefinition $fibCode -CodeDomProvider $FSharpCodeProvider

    # Test
    [Fibonacci]::get(5)
}

Use fake


Invoke-Command -ComputerName SECOND -ScriptBlock {
    # Cache
    $tools = 'C:\Tools'

    if (-not (Test-Path -Path $tools)) {
        New-Item -Path $tools -ItemType 'directory'
    }

    Set-Location $tools

    # Libs
    @('FSharp.Compiler.CodeDom', 'FAKE') | ? {
        -not (Get-ChildItem -Path (Join-Path -Path $tools -ChildPath "$_*"))
    } | % {
        nuget install $_
    }

    # Include
    Add-Type -Path 'C:\Program Files (x86)\Reference Assemblies\Microsoft\FSharp\.NETFramework\v4.0\4.3.1.0\FSharp.Core.dll'
    Get-ChildItem -Path C:\Tools\FSharp.Compiler.CodeDom.*\lib\net40\FSharp.Compiler.CodeDom.dll | % { Add-Type -Path $_.FullName  }

    Get-ChildItem -Path C:\Tools\Fake.*\tools\FakeLib.dll | % {
        $FakeLib = $_.FullName
        Add-Type -Path $_.FullName
    }

    Get-ChildItem -Path C:\Tools\Fake.*\tools | % {
        $FakePath = $_.FullName
        $env:Path = "$env:Path;$($_.FullName)"
    }

    # Script
    $code = `
'
module FakeTest

open Fake

Target "Test" (fun _ ->
    trace "Testing stuff..."
)

Target "Deploy" (fun _ ->
    trace "Heavy deploy action"
)

Run "Deploy"
'

    # Compile
    $FSharpCodeProvider = New-Object FSharp.Compiler.CodeDom.FSharpCodeProvider
    Add-Type -TypeDefinition $code -CodeDomProvider $FSharpCodeProvider -ReferencedAssemblies $FakeLib  -IgnoreWarnings

    # Do something about it
    [FakeTest]
}

Conclusion

I have managed to successfully execute remote F# on demand compilation with FAKE libraries on dependencies, what proves the concept as valid. Thus, mentioned kind of strong typed DSL is possible to implement with integration with WinRM and PowerShell to build good CM system for Windows platform.

Due to the very complex toolset required for the compilation of the script, inability of these tools to be deployed smoothly in quite mode remotely, big time required for the dynamically loaded compiler to initialise it self and actually do the compilation, I think it makes more sense to execute only locally compiled scripts, configurations and batches providing to the remote site only binary modules to run.

Hints

  • To view available modules Get-Module –ListAvailable
  • Show environment Get-ChildItem env:
  • Where did FSharp.Compiler.CodeDom go? GitHub PowerPack archive issue 21

Links

Its based on the following articles:

  • https://blogs.msdn.microsoft.com/fsharpteam/2012/10/03/rethinking-findstr-with-f-and-powershell/
  • http://tahirhassan.blogspot.ru/2014/06/embedding-f-in-powershell-hacky-way.html
  • http://www.old.dougfinke.com/blog/index.php/2007/07/27/embedding-f-in-powershell/
  • http://tahirhassan.blogspot.ru/2014/06/embedding-f-in-powershell.html
  • http://fsharp.github.io/FSharp.Compiler.Service/
  • http://stackoverflow.com/questions/17111622/f-environment-integration-for-scripting
  • http://get-powershell.com/post/2008/12/30/Inline-F-in-PowerShell.aspx
  • http://stackoverflow.com/questions/30171272/using-f-script-replace-powershell-in-production-environment
  • https://github.com/fsprojects/FSharp.Management
  • https://sergeytihon.wordpress.com/2013/08/04/powershell-type-provider/
  • http://fsprojects.github.io/FSharp.Management/PowerShellProvider.html
  • https://www.simple-talk.com/sysadmin/powershell/practical-powershell-unit-testing-getting-started/
  • https://github.com/pester/Pester
  • https://github.com/fsharp/FAKE
  • https://github.com/joeyh/propellor
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