Throttling Resource Manager requests

  • 4 minutes to read
  • Contributors
    • Tom FitzMacken
    • Jonathan Gao
    • Ryan Jones

For each Azure subscription and tenant, Resource Manager allows up to 12,000 read requests per hour and 1,200 write requests per hour. These limits are scoped to the principal ID making the requests and the subscription ID or tenant ID. If your requests come from more than one principal ID, your limit across the subscription or tenant is greater than 12,000 and 1,200 per hour.

Requests are applied to either your subscription or your tenant. Subscription requests are ones the involve passing your subscription ID, such as retrieving the resource groups in your subscription. Tenant requests don't include your subscription ID, such as retrieving valid Azure locations.

These limits apply to each Azure Resource Manager instance. There are multiple instances in every Azure region, and Azure Resource Manager is deployed to all Azure regions. So, in practice, limits are effectively much higher than these limits, as user requests are usually serviced by many different instances.

If your application or script reaches these limits, you need to throttle your requests. This article shows you how to determine the remaining requests you have before reaching the limit, and how to respond when you've reached the limit.

When you reach the limit, you receive the HTTP status code 429 Too many requests.

Azure Resource Graph limits the number of requests to its operations. The steps in this article to determine the remaining requests and how to respond when the limit is reached also apply to Resource Graph. However, Resource Graph sets its own limit and reset rate. For more information, see Throttle in Azure Resource Graph.

Remaining requests

You can determine the number of remaining requests by examining response headers. Read requests return a value in the header for the number of remaining read requests. Write requests include a value for the number of remaining write requests. The following table describes the response headers you can examine for those values:

Response header Description
x-ms-ratelimit-remaining-subscription-reads Subscription scoped reads remaining. This value is returned on read operations.
x-ms-ratelimit-remaining-subscription-writes Subscription scoped writes remaining. This value is returned on write operations.
x-ms-ratelimit-remaining-tenant-reads Tenant scoped reads remaining
x-ms-ratelimit-remaining-tenant-writes Tenant scoped writes remaining
x-ms-ratelimit-remaining-subscription-resource-requests Subscription scoped resource type requests remaining.

This header value is only returned if a service has overridden the default limit. Resource Manager adds this value instead of the subscription reads or writes.
x-ms-ratelimit-remaining-subscription-resource-entities-read Subscription scoped resource type collection requests remaining.

This header value is only returned if a service has overridden the default limit. This value provides the number of remaining collection requests (list resources).
x-ms-ratelimit-remaining-tenant-resource-requests Tenant scoped resource type requests remaining.

This header is only added for requests at tenant level, and only if a service has overridden the default limit. Resource Manager adds this value instead of the tenant reads or writes.
x-ms-ratelimit-remaining-tenant-resource-entities-read Tenant scoped resource type collection requests remaining.

This header is only added for requests at tenant level, and only if a service has overridden the default limit.

Retrieving the header values

Retrieving these header values in your code or script is no different than retrieving any header value.

For example, in C#, you retrieve the header value from an HttpWebResponse object named response with the following code:

response.Headers.GetValues("x-ms-ratelimit-remaining-subscription-reads").GetValue(0)

In PowerShell, you retrieve the header value from an Invoke-WebRequest operation.

$r = Invoke-WebRequest -Uri https://management.azure.com/subscriptions/{guid}/resourcegroups?api-version=2016-09-01 -Method GET -Headers $authHeaders
$r.Headers["x-ms-ratelimit-remaining-subscription-reads"]

For a complete PowerShell example, see Check Resource Manager Limits for a Subscription.

If you want to see the remaining requests for debugging, you can provide the -Debug parameter on your PowerShell cmdlet.

Get-AzResourceGroup -Debug

Which returns many values, including the following response value:

DEBUG: ============================ HTTP RESPONSE ============================

Status Code:
OK

Headers:
Pragma                        : no-cache
x-ms-ratelimit-remaining-subscription-reads: 11999

To get write limits, use a write operation:

New-AzResourceGroup -Name myresourcegroup -Location westus -Debug

Which returns many values, including the following values:

DEBUG: ============================ HTTP RESPONSE ============================

Status Code:
Created

Headers:
Pragma                        : no-cache
x-ms-ratelimit-remaining-subscription-writes: 1199

In Azure CLI, you retrieve the header value by using the more verbose option.

az group list --verbose --debug

Which returns many values, including the following values:

msrest.http_logger : Response status: 200
msrest.http_logger : Response headers:
msrest.http_logger :     'Cache-Control': 'no-cache'
msrest.http_logger :     'Pragma': 'no-cache'
msrest.http_logger :     'Content-Type': 'application/json; charset=utf-8'
msrest.http_logger :     'Content-Encoding': 'gzip'
msrest.http_logger :     'Expires': '-1'
msrest.http_logger :     'Vary': 'Accept-Encoding'
msrest.http_logger :     'x-ms-ratelimit-remaining-subscription-reads': '11998'

To get write limits, use a write operation:

az group create -n myresourcegroup --location westus --verbose --debug

Which returns many values, including the following values:

msrest.http_logger : Response status: 201
msrest.http_logger : Response headers:
msrest.http_logger :     'Cache-Control': 'no-cache'
msrest.http_logger :     'Pragma': 'no-cache'
msrest.http_logger :     'Content-Length': '163'
msrest.http_logger :     'Content-Type': 'application/json; charset=utf-8'
msrest.http_logger :     'Expires': '-1'
msrest.http_logger :     'x-ms-ratelimit-remaining-subscription-writes': '1199'

Waiting before sending next request

When you reach the request limit, Resource Manager returns the 429 HTTP status code and a Retry-After value in the header. The Retry-After value specifies the number of seconds your application should wait (or sleep) before sending the next request. If you send a request before the retry value has elapsed, your request isn't processed and a new retry value is returned.

Next steps