Powershell to backup a CosmosDB

CosmosDBBkup.ps1

<#
    This script will call the cosmos db migration tool with the correct parameters based
    on a list of databases that need to be backed up. It depends on a json param file that
    contains the list of cosmos db services that have databases that require backup.

    This script has a couple of dependencies: 
    
    (1) the dt.exe that it runs (the cosmos db migration tool and we assume the associated files/dlls
    in the compiled folder) needs to be locally available.

    (2) A configured json file to list out the cosmos services and databases that require backups. 
    Care should be taken (encrypt the file and provide access to the keys to a limited set of users)
    as the read-only keys for the cosmos-db service will be stored here.
#>

$retentionDays = 14
$backupList = "C:\temp\CosmosBackup.json" # point these at the appropriate folders
$backupPath = 'C:\temp\'
$pathtoEXE = 'C:\temp\drop\dt.exe'
$backups = Get-Content -Raw -Path $backupList | ConvertFrom-Json

foreach($s in $backups.service)
{
    $sName = $s.name
    Write-Output "Processing service $sName..."
    $cosmosConnectString = $s.connectString

    foreach($d in $s.databases)
    {
        $database = $d.name
        if ($d.backupFlag -eq $true)
        {
            Write-Output "  Backing up collections in $database..."

            foreach($c in $d.collections)
            {
                $collection = $c.name
                Write-Output "      Backing up collection $collection."
                <# configure export arguments #>
                $connectString = "$cosmosConnectString;Database=$database"
                $date = Get-Date
                $dateString = $date.ToString('yyyyMMdd')
                $dateString = $dateString + '_' + $date.ToString('hhmm')
                $targetFile = "$collection`_$dateString.json"
 
                $args = "/ErrorLog:" + "$backupPath\backups\$sName\$database\$collection`_$dateString`_log.csv /OverwriteErrorLog"
                $args = $args + " /ErrorDetails:Critical /s:DocumentDB /s.ConnectionString:$connectString"
                $args = $args + " /s.ConnectionMode:Gateway /s.Collection:$collection /s.Query:`"SELECT * FROM c`""
                $args = $args + " /t:JsonFile /t.File:$backupPath\backups\$Name\$database\$targetFile /t.Prettify /t.Overwrite"                

                <# now we are all configured: run the collection backup #>
                Start-Process -FilePath $pathtoEXE -ArgumentList $args -Wait
            }
        }
        else {
            Write-Output "  Skipping $dName backupFlag <> true."
        }
    }
}

$purgeDate = (Get-Date).AddDays(-1 * ($retentionDays + 1))

<# remove old logs and backups #>
Get-ChildItem -Path $backupPath -Recurse -Include *.json -Exclude *cosmosBackup.json | Where-Object {$_.CreationTime -lt $purgeDate} | Remove-Item 
Get-ChildItem -Path $backupPath -Recurse -Include *.csv | Where-Object {$_.CreationTime -lt $purgeDate} | Remove-Item