I’ve been exploring the Sync Framework for use in a couple of projects I have going and PowerShell is my preferred exploratory environment.

It was a bit of fun, since I got to work with eventing for the first time in V2.

First, I downloaded the Sync Framework Software Development Kit.  That provided me with the Sync Framework runtime as well as some documentation.

The easiest way for me to get started was to take one of the samples and convert that to PowerShell.

I’m going to walk along the MSDN Sample and provide the equivalent PowerShell, as well as any changes I made to make it feel more PowerShell-y.

Setting Synchronization Options

We are working with the File Sync Provider First up is setting the FileSyncOptions.  FileSyncOptions are an enumeration (a limited list defined in code that maps to certain values) whose values are controlled by setting the appropriate bits to indicate the presence or absence of a flag.  Mark Schill has a great post about how to set bitwise operations.

$options = [Microsoft.Synchronization.Files.FileSyncOptions]::ExplicitDetectChanges
$options = $options -bor [Microsoft.Synchronization.Files.FileSyncOptions]::RecycleDeletedFiles
$options = $options -bor [Microsoft.Synchronization.Files.FileSyncOptions]::RecyclePreviousFileOnUpdates
$options = $options -bor [Microsoft.Synchronization.Files.FileSyncOptions]::RecycleConflictLoserFiles

Specifying a Static Filter

With the File System provider, we can provide filters to include or exclude files and directories.

$FileNameFilter and $SubdirectoryNameFilter are parameters that take strings or string arrays.

$filter = New-Object Microsoft.Synchronization.Files.FileSyncScopeFilter
if ($FileNameFilter.count -gt 0)
{
   $FileNameFilter | ForEach-Object { $filter.FileNameExcludes.Add($_) }
}
if ($SubdirectoryNameFilter.count -gt 0)
{
   $SubdirectoryNameFilter | ForEach-Object { $filter.SubdirectoryExcludes.Add($_) }
}

Performing Change Detection

After configuring the filter, we examine the folders and files located at the paths specified.  If there has not been any previous synchronization, a metadata file will be created in each location to track any changes, updates, and deletes for later synchronization.

function Get-FileSystemChange()
{
    param ($path, $filter, $options)
    try
    {
        $provider = new-object Microsoft.Synchronization.Files.FileSyncProvider -ArgumentList $path, $filter, $options
        $provider.DetectChanges()
    }
    finally
    {
        if ($provider -ne $null)
        {
            $provider.Dispose()
        }
    }
}

Get-FileSystemChange $SourcePath $filter $options
Get-FileSystemChange $DestinationPath $filter $options

Handling Conflicts

Conflict resolution in the Sync Framework happens at the at the event level.  An event is merely something that happens that can trigger other actions.  Using Register-ObjectEvent, we can associate one or more scriptblocks with an event.

First, I defined scriptblocks to handle the conflicts.  There is an enumeration, the ConflictResolutionAction enumeration, that provides some options for dealing with conflicts.  For this example, we are going to pick the source object as the winner for any conflicts.

You will also notice another type of conflict defined, and that is a Constraint conflict.  That can occur when an object of the same name is added on both sides in between synchronizations.  The resolution options for these conflicts can be found in the ConstraintConflictResolutionAction enumeration.

$ItemConflictAction =   {
    $event.SourceEventArgs.SetResolutionAction([Microsoft.Synchronization.ConflictResolutionAction]::SourceWins)
    [string[]]$global:FileSyncReport.Conflicted += $event.SourceEventArgs.DestinationChange.ItemId
}
$ItemConstraintAction = {
     $event.SourceEventArgs.SetResolutionAction([Microsoft.Synchronization.ConstraintConflictResolutionAction]::SourceWins)
     [string[]]$global:FileSyncReport.Constrained += $event.SourceEventArgs.DestinationChange.ItemId
}            

# Configure the events for conflicts or constraints for the source and destination providers
$destinationCallbacks = $destinationProvider.DestinationCallbacks
Register-ObjectEvent -InputObject $destinationCallbacks -EventName ItemConflicting -Action $ItemConflictAction | Out-Null
Register-ObjectEvent -InputObject $destinationCallbacks -EventName ItemConstraint -Action $ItemConstraintAction | Out-Null            

$sourceCallbacks = $SourceProvider.DestinationCallbacks
Register-ObjectEvent -InputObject $sourceCallbacks -EventName ItemConflicting -Action $ItemConflictAction | Out-Null
Register-ObjectEvent -InputObject $sourceCallbacks -EventName ItemConstraint -Action $ItemConstraintAction | Out-Null

We also see for the first time in the script blocks a variable called $event.  This is an automatic variable exposed by the event and provides us information that we can use in our action.

Finally, I’m updating a variable in the global scope.  There probably is a better way to handle this, but scriptblocks executed in response to events only have access to the global scope and any of the automatic variable exposed to it.  Therefore, I use a variable in the global scope to gather my reporting information.

Synchronizing Two Replicas

To start to synchronize the two sides, first we set up the synchronization via a SyncOrchestrator and assign it the local and remote providers, as well as defining the direction of the synchronization.  In this example (sticking with the format from MSDN, we will do an Upload, which is in the SyncDirectionOrder enumeration (other options are Download, DownloadAndUpload, and UploadAndDownload). 

# Create the agent that will perform the file sync
$agent = New-Object  Microsoft.Synchronization.SyncOrchestrator
$agent.LocalProvider = $sourceProvider
$agent.RemoteProvider = $destinationProvider            

# Upload changes from the source to the destination.
$agent.Direction = [Microsoft.Synchronization.SyncDirectionOrder]::Upload            

Write-Host "Synchronizing changes from $($sourceProvider.RootDirectoryPath) to replica: $($destinationProvider.RootDirectoryPath)"
$agent.Synchronize();

To achieve two way synchronization, we will do the upload twice, reversing the order of the providers.

Invoke-OneWayFileSync -SourcePath $SourcePath -DestinationPath $DestinationPath -Filter $null -Options $options
Invoke-OneWayFileSync -SourcePath $DestinationPath -DestinationPath $SourcePath -Filter $null -Options $options

Full Example

I modified the example to write out a custom object (and the logging is in the variable in the global scope as noted in the Handling Conflicts section) with the results of the synchronization (rather than logging it to the console).

In all, my translation is pretty similar to the example code, but there are some differences. 

# Requires -Version 2
# Also depends on having the Microsoft Sync Framework 2.0 SDK or Runtime
# --SDK--
# http://www.microsoft.com/downloads/details.aspx?FamilyID=89adbb1e-53ff-41b5-ba17-8e43a2e66254&displaylang=en
# --Runtime--
# http://www.microsoft.com/downloads/details.aspx?FamilyId=109DB36E-CDD0-4514-9FB5-B77D9CEA37F6&displaylang=en
#
#            

[CmdletBinding(SupportsShouldProcess=$true)]
param (
    [Parameter(Position=1, Mandatory=$true, ValueFromPipelineByPropertyName=$true)]
    [Alias('FullName', 'Path')]
    [string]$SourcePath
    , [Parameter(Position=2, Mandatory=$true)]
    [string]$DestinationPath
    , [Parameter(Position=3)]
    [string[]]$FileNameFilter
    , [Parameter(Position=4)]
    [string[]]$SubdirectoryNameFilter
)
<#
    .Synopsis
        Synchronizes to directory trees
    .Description
        Examines two directory structures (SourcePath and DestinationPath) and uses the Microsoft Sync Framework
        File System Provider to synchronize them.
    .Example
        An example of using the command
#>
begin
{
    [reflection.assembly]::LoadWithPartialName('Microsoft.Synchronization') | Out-Null
    [reflection.assembly]::LoadWithPartialName('Microsoft.Synchronization.Files') | Out-Null            

    function Get-FileSystemChange()
    {
        param ($path, $filter, $options)
        try
        {
            $provider = new-object Microsoft.Synchronization.Files.FileSyncProvider -ArgumentList $path, $filter, $options
            $provider.DetectChanges()
        }
        finally
        {
            if ($provider -ne $null)
            {
                $provider.Dispose()
            }
        }
    }            

    function Invoke-OneWayFileSync()
    {
        param ($SourcePath, $DestinationPath,
                    $Filter, $Options)
        $ApplyChangeJobs = @()
        $AppliedChangeJobs = @()
        try
        {
            # Scriptblocks to handle the events raised during synchronization
            $AppliedChangeAction = {
                $argument = $event.SourceEventArgs
                switch ($argument.ChangeType)
                {
                    { $argument.ChangeType -eq [Microsoft.Synchronization.Files.ChangeType]::Create } {[string[]]$global:FileSyncReport.Created += $argument.NewFilePath}
                    { $argument.ChangeType -eq [Microsoft.Synchronization.Files.ChangeType]::Delete } {[string[]]$global:FileSyncReport.Deleted += $argument.OldFilePath}
                    { $argument.ChangeType -eq [Microsoft.Synchronization.Files.ChangeType]::Update } {[string[]]$global:FileSyncReport.Updated += $argument.OldFilePath}
                    { $argument.ChangeType -eq [Microsoft.Synchronization.Files.ChangeType]::Rename } {[string[]]$global:FileSyncReport.Renamed += $argument.OldFilePath}
                }
            }            

            $SkippedChangeAction = {
                [string[]]$global:FileSyncReport.Skipped += $event.SourceEventArgs.CurrentFilePath            

                if ($event.SourceEventArgs.Exception -ne $null)
                {
                    Write-Error '[' + "$($event.SourceEventArgs.Exception.Message)" +']'
                }
            }            

            # Create source provider and register change events for it            

            $sourceProvider = New-Object Microsoft.Synchronization.Files.FileSyncProvider -ArgumentList $SourcePath, $filter, $options
            $AppliedChangeJobs += Register-ObjectEvent -InputObject $SourceProvider -EventName AppliedChange -Action $AppliedChangeAction
            $AppliedChangeJobs += Register-ObjectEvent -InputObject $SourceProvider -EventName SkippedChange -Action $SkippedChangeAction             

            $ApplyChangeJobs += $SourceApplyChangeJob            

            # Create destination provider and register change events for it
            $destinationProvider = New-Object Microsoft.Synchronization.Files.FileSyncProvider -ArgumentList $DestinationPath, $filter, $options
            $AppliedChangeJobs += Register-ObjectEvent -InputObject $destinationProvider -EventName AppliedChange -Action $AppliedChangeAction
            $AppliedChangeJobs += Register-ObjectEvent -InputObject $destinationProvider -EventName SkippedChange -Action $SkippedChangeAction            

            $ApplyChangeJobs += $DestApplyChangeJob            

            # Use scriptblocks for the SyncCallbacks for conflicting items.
            $ItemConflictAction =   {
                $event.SourceEventArgs.SetResolutionAction([Microsoft.Synchronization.ConflictResolutionAction]::SourceWins)
                [string[]]$global:FileSyncReport.Conflicted += $event.SourceEventArgs.DestinationChange.ItemId
            }
            $ItemConstraintAction = {
                $event.SourceEventArgs.SetResolutionAction([Microsoft.Synchronization.ConstraintConflictResolutionAction]::SourceWins)
                [string[]]$global:FileSyncReport.Constrained += $event.SourceEventArgs.DestinationChange.ItemId
            }            

            #Configure the events for conflicts or constraints for the source and destination providers
            $destinationCallbacks = $destinationProvider.DestinationCallbacks
            $AppliedChangeJobs += Register-ObjectEvent -InputObject $destinationCallbacks -EventName ItemConflicting -Action $ItemConflictAction
            $AppliedChangeJobs += Register-ObjectEvent -InputObject $destinationCallbacks -EventName ItemConstraint -Action $ItemConstraintAction             

            $sourceCallbacks = $SourceProvider.DestinationCallbacks
            $AppliedChangeJobs += Register-ObjectEvent -InputObject $sourceCallbacks -EventName ItemConflicting -Action $ItemConflictAction
            $AppliedChangeJobs += Register-ObjectEvent -InputObject $sourceCallbacks -EventName ItemConstraint -Action $ItemConstraintAction             

            # Create the agent that will perform the file sync
            $agent = New-Object  Microsoft.Synchronization.SyncOrchestrator
            $agent.LocalProvider = $sourceProvider
            $agent.RemoteProvider = $destinationProvider            

            # Upload changes from the source to the destination.
            $agent.Direction = [Microsoft.Synchronization.SyncDirectionOrder]::Upload            

            Write-Host "Synchronizing changes from $($sourceProvider.RootDirectoryPath) to replica: $($destinationProvider.RootDirectoryPath)"
            $agent.Synchronize();
        }
        finally
        {
            # Release resources.
            if ($sourceProvider -ne $null) {$sourceProvider.Dispose()}
            if ($destinationProvider -ne $null) {$destinationProvider.Dispose()}
        }
    }            

    # Set options for the synchronization session. In this case, options specify
    # that the application will explicitly call FileSyncProvider.DetectChanges, and
    # that items should be moved to the Recycle Bin instead of being permanently deleted.            

    $options = [Microsoft.Synchronization.Files.FileSyncOptions]::ExplicitDetectChanges
    $options = $options -bor [Microsoft.Synchronization.Files.FileSyncOptions]::RecycleDeletedFiles
    $options = $options -bor [Microsoft.Synchronization.Files.FileSyncOptions]::RecyclePreviousFileOnUpdates
    $options = $options -bor [Microsoft.Synchronization.Files.FileSyncOptions]::RecycleConflictLoserFiles
}
process
{
    $filter = New-Object Microsoft.Synchronization.Files.FileSyncScopeFilter
    if ($FileNameFilter.count -gt 0)
    {
       $FileNameFilter | ForEach-Object { $filter.FileNameExcludes.Add($_) }
    }
    if ($SubdirectoryNameFilter.count -gt 0)
    {
       $SubdirectoryNameFilter | ForEach-Object { $filter.SubdirectoryExcludes.Add($_) }
    }            

    # Perform the detect changes operation on the two file locations
    Get-FileSystemChange $SourcePath $filter $options
    Get-FileSystemChange $DestinationPath $filter $options            

    # Reporting Object - using the global scope so that it can be updated by the event scriptblocks.
    $global:FileSyncReport = New-Object PSObject |
        Select-Object SourceStats, DestinationStats, Created, Deleted, Overwritten, Renamed, Skipped, Conflicted, Constrained            

    # We don't need to pass any filters here, since we are using the file detection that was previously completed.
    # this will only 
    $global:FileSyncReport.SourceStats = Invoke-OneWayFileSync -SourcePath $SourcePath -DestinationPath $DestinationPath -Filter $null -Options $options
    $global:FileSyncReport.DestinationStats = Invoke-OneWayFileSync -SourcePath $DestinationPath -DestinationPath $SourcePath -Filter $null -Options $options            

    # Write result to pipeline
    Write-Output $global:FileSyncReport
}

Download Invoke-SyncFrameworkSample.zip