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Powershell to backup a CosmosDB
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 = $
Write-Output "Processing service $sName..."
$cosmosConnectString = $s.connectString
foreach($d in $s.databases)
$database = $
if ($d.backupFlag -eq $true)
Write-Output " Backing up collections in $database..."
foreach($c in $d.collections)
$collection = $
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
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