Throttling and quotas: HTTP 429 and snapshot limits

1Read the limits Azure already tells you

Run a normal command with debug output and pick out the rate-limit headers:

az group list --debug 2>&1 | Select-String 'x-ms-ratelimit-remaining' | Select-Object -First 3

You should see something like this (numbers vary):

DEBUG: cli.azure.cli.core.sdk.policies:     'x-ms-ratelimit-remaining-subscription-reads': '249'
DEBUG: cli.azure.cli.core.sdk.policies:     'x-ms-ratelimit-remaining-subscription-global-reads': '15999'
DEBUG: cli.azure.cli.core.sdk.policies:     'x-ms-ratelimit-remaining-tenant-reads': '249'

Every Resource Manager response carries these. A script that logs them sees throttling coming long before it happens.

2A disk and its first incremental snapshot

Create a small disk and take one incremental snapshot:

az group create --name rg-saat-l68 --location centralindia --tags course=saatvedha-azure lesson=68 -o none
az disk create --resource-group rg-saat-l68 --name disk-l68 --size-gb 4 --sku StandardSSD_LRS -o none
$diskId = az disk show --resource-group rg-saat-l68 --name disk-l68 --query id -o tsv
az snapshot create --resource-group rg-saat-l68 --name snap-l68-0 --source $diskId --incremental true --query "{name:name, incremental:incremental, state:provisioningState}" -o table

You should see something like this:

Name        Incremental    State
----------  -------------  ---------
snap-l68-0  True           Succeeded

3Save the two scripts

Save this as C:\azure-lab\l68\Test-GraphBurst.ps1:

# SaatVedha Azure Lesson 68: send 30 Resource Graph queries as fast as possible
$token = az account get-access-token --resource https://management.azure.com --query accessToken -o tsv
$headers = @{ Authorization = "Bearer $token"; 'Content-Type' = 'application/json' }
$url = 'https://management.azure.com/providers/Microsoft.ResourceGraph/resources?api-version=2022-10-01'
$body = '{"query":"Resources | summarize count()"}'
$ok = 0; $throttled = 0
foreach ($i in 1..30) {
    try { Invoke-RestMethod -Method Post -Uri $url -Headers $headers -Body $body | Out-Null; $ok++ }
    catch { if ($_.Exception.Response.StatusCode.value__ -eq 429) { $throttled++ } else { throw } }
}
"OK: $ok   Throttled (429): $throttled"

And this as C:\azure-lab\l68\Invoke-GraphWithRetry.ps1:

# SaatVedha Azure Lesson 68: Resource Graph query that backs off on HTTP 429
function Invoke-GraphWithRetry {
    param([Parameter(Mandatory)][string]$Query, [int]$MaxTries = 6)
    $token = az account get-access-token --resource https://management.azure.com --query accessToken -o tsv
    $headers = @{ Authorization = "Bearer $token"; 'Content-Type' = 'application/json' }
    $url = 'https://management.azure.com/providers/Microsoft.ResourceGraph/resources?api-version=2022-10-01'
    $body = @{ query = $Query } | ConvertTo-Json
    for ($try = 1; $try -le $MaxTries; $try++) {
        try { return Invoke-RestMethod -Method Post -Uri $url -Headers $headers -Body $body }
        catch {
            if ($_.Exception.Response.StatusCode.value__ -ne 429) { throw }
            $wait = [math]::Min(30, [math]::Pow(2, $try))
            $reset = $_.Exception.Response.Headers['x-ms-user-quota-resets-after']
            if ($reset) { $wait = [math]::Ceiling(([timespan]$reset).TotalSeconds) + 1 }
            Write-Host "429 received, waiting $wait s (try $try of $MaxTries)"
            Start-Sleep -Seconds $wait
        }
    }
    throw "Still throttled after $MaxTries tries"
}

✅ Checkpoint: You can see ARM’s remaining-request headers, you have a disk with one incremental snapshot, and both scripts are saved.