Powershell script to query cosmosdb services for a list of databases and containers in them.

ListCosmosDBContainers.ps1

<#
    Author:     Josh Smith
    Created:    2020-03-02

    Purpose:    Will pull all databases and containers from known CosmosDB resources.
    Cosmos db services must be known and added to the array below (paired with the
    associated resource group).

#>
<# add cosmos db resource and groups here as needed: #>
$cosmosDBServices = @( @{resource = '<cosmos db service 1>'; group = '<resource group name>'}, `
    @{resource = '<cosmos db service 2'; group = '<resource group name>'})


$connectAz = Read-Host "Did you already connect to Azure [Y/N]?"
# Sadly the need to authenticate with Azure means this script needs to be run manually.
if ($connectAz -eq 'N'){Connect-AzAccount -subscriptionName "<name of your Azure subscription>"}

$dbResourceType = "Microsoft.DocumentDb/databaseAccounts/apis/databases"
$containerResourceType = "Microsoft.DocumentDb/databaseAccounts/apis/databases/containers"
$BackupStorageName = "<Azure storage account name>"
$StorageResourceGroupName = "<resource group for azure storage>"
$apiVersion = "2015-04-08"
$finalJson = ""

foreach($c in $cosmosDBServices)
{
    $ResourceName = $c.resource + "/sql/"
    $resourceGroup = $c.group

    $databases = Get-AzResource -ResourceType $dbResourceType -ApiVersion $apiVersion `
        -ResourceGroupName $resourceGroup -Name $ResourceName | `
        Select-Object -ExpandProperty Properties | Select-Object id
    
    foreach($d in $databases)
    {
        $databaseName = $d.id

        $db = $ResourceName + $databaseName
        
        $containers = Get-AzResource -ResourceType $containerResourceType `
            -ApiVersion $apiVersion -ResourceGroupName $ResourceGroup `
            -Name $db | Select-Object -ExpandProperty Properties | Select-Object id
        
        foreach($con in $containers)
        {
            $container = $con.id

            $con = $null
            $json = $null
            $conObject = New-Object -TypeName psobject
            $conObject | Add-Member -MemberType NoteProperty -Name ContainerName -Value $container
            $conObject | Add-Member -MemberType NoteProperty -Name DatabaseName -Value $databaseName
            $conObject | Add-Member -MemberType NoteProperty -Name ResourceName -Value $resourceName.Substring(0, $resourceName.Length - 5)

            $json = $conObject | ConvertTo-Json

            $finalJson = $finalJson + $json + ",
"    # I'm a sucker for lazy line breaks
        }
    }
}

# lose the last line break and comma then output:
$finalJson = $finalJson.Substring(0, $finalJson.Length - 2)
$finalJson | Out-File -FilePath '.\CDBBackup.json' -Force

# connect to the blob storage and then push the file up:
$storageAccount = Get-AzStorageAccount -ResourceGroupName $StorageResourceGroupName `
    -Name $BackupStorageName 

$storageContext = $storageAccount.Context

Set-AzStorageBlobContent -File '.\CDBBackup.json' -Container 'backuplist' `
    -Blob 'CDBBackups.json' -Context $storageContext -Force

# don't need that file hanging around here:
Remove-Item .\CDBBackup.json