resume_session.ps1

resume_session.ps1

## ScriptName: last_session.ps1
## author: David Midlo ([email protected])
##
## Purpose: This PowerShell script is designed as a proof of concept for resuming a long-running 
## process in a script that processes user accounts from Active Directory. The script stores progress
## in a file (`USERS.clixml`) so that it can resume from where it left off if interrupted, avoiding the
## need to restart from the beginning. This is particularly useful for environments
## where processing large numbers of user accounts may take significant time.
##
## Disclaimer: No warranty and all that! This is a proof of concept script only! There is no
## error handling or anything that would potentially obscure how this operation is functioning.
## (Except for "write-progress" which is vital to not going insane while waiting for hours for
## a process to complete.)
##
## ### Key Components:
## 1. **Initialization:**
##   - Imports the Active Directory module as a proxy example for any long-list of work to be done.
##   - Clears any previous session variables.
##   - Defines the organizational unit (OU) to search for users within Active Directory.
##   - Initializes two hash tables:
##     - `$ImportedUserHash`: Stores users processed in previous runs.
##     - `$CurrentSessionUserHash`: Tracks users processed in the current session.
##
## 2. **Import Previous Run Data:**
##   - Attempts to import previously processed users from the `USERS.clixml` file. 
##     If the file is not found, it handles the error and continues.
##
## 3. **Fetch Users:**
##   - Retrieves a list of users from Active Directory based on the specified OU.
##
## 4. **Progress Tracking:**
##   - Counts the number of users retrieved and the number already processed from previous runs.
##   - Displays this information to the host.
##
## 5. **Processing Users:**
##   - Iterates over each user retrieved from Active Directory.
##   - If the user was processed in a previous run, it skips to the next user and logs this.
##   - If the user has not been processed, it:
##     - Waits for 3 seconds (as a placeholder for actual processing).
##     - Adds the user to the `$ImportedUserHash` hash table.
##     - Exports the updated hash table to `USERS.clixml`.
##     - Logs the processing of the user.
##
## 6. **Progress Bar:**
##   - Updates a progress bar with the percentage of users processed and the current user being processed.
##
#######################################################################################

## clean up the variables for consecutive runs.

Import-Module activedirectory
Clear-Host
$user = $null
$users = $null
$ClixmlUsers = $null
$rootDN = $null
$ImportedUserHash = $null
$CurrentSessionUserHash = $null

#######################################################################################

## Define the OU
$rootDN = "OU=Users,DC=your,DC=com"

## Initilize HashTables $importeduserhash is the datasource, $CurrentSessionUserHash is a post-run diagnostics variable
$ImportedUserHash = @{}
$CurrentSessionUserHash = @{}

## Import Previous Runs
try {
  $ErrorActionPreference = "Stop"
  $ImportedUserHash = Import-Clixml .\USERS.clixml
}
catch
{
  # Disregard File Not Found error as we will be creating USERS.clixml if doesn't already exist.
  if ($_.Exception.message -notmatch "Could not find file") {
    throw $_
  }
}

## Get List of Users From Active Directory
$Users = @(Get-ADUser -filter * -SearchScope subtree -SearchBase "$rootDN" -Properties sAMAccountName,distinguishedName,homedirectory)

## Setup Variables for Write-Progress
$a = $users.Count
$b = $ImportedUserHash.count

## Notify Host of Current Progress Numbers
write-host "imported completed user count is:" $b
write-host "Active Directory user count is:" $a

## Begin Labor Loop
foreach($user in $Users){
  ## Check to see if User was completed in a previous run
  if($ImportedUserHash.Contains($user.SamAccountName)){
    ## Notify Host that user has already been run in a previous session
    Write-Host $user.SamAccountName "completed in previous session" -ForegroundColor Yellow
    
    ## Add to diagnostics variable with value set at "imported from previous session.
    $CurrentSessionUserHash.add($user.SamAccountName,"Imported From Previous Session")
  }
  ## If user has not been run previously, take action now
  Else{
    ## wait just to give the script something to do to waste time for a demo
    ## This is where you would actually add your functional work to be done.
    Start-Sleep -Seconds 3
    
    ## add user completed user to hashtable for export. This should always be the last functinal step in the foreach...
    $ImportedUserHash.add($user.SamAccountName,$user.DistinguishedName)
    
    ## Export hashtable to clixml. I chose clixml instead of csv for two reasons; one, it imports as the variable as it was
    ## exported as. Two, it will be less likely to be deleted by some other admin.
    $ImportedUserHash | Export-Clixml .\USERS.clixml

    ## add user to diagnostics variable with value set to "current session"
    $CurrentSessionUserHash.add($user.SamAccountName,"Current Session")

    ## notify host things went well
    write-host $user.sAMAccountName "has been added to User Hashtable"-ForegroundColor Green
    ## +1 to the write-progress count
    $b++
  }

## percent of whole calculator for write-progress
$c = ($b / $a) * 100

## update progress bar with current statistics.
write-progress -activity Updating -status 'Progress->' -percentcomplete $c -currentOperation "Profiles Completed: $b of $a Percent Complete: $c Current Accout: $user."
}