The image registry operator in Azure by default has two replicas.  Every 5 minutes, each of those replicas makes a call to the StorageAccount List operation for the image registry storage account.  

Azure has published limits for storage account throttling operations.  These limits are 100 calls to list operations every 5 minutes based on the subscription & region pair that exists. 

Because of this, customers are limited to <50 clusters per subscription and region in Azure.  This number can change based on the number of image registry replicas as well as customer activity on List storage account operations within that subscription and region.  

On Azure Red Hat OpenShift managed service, we occasionally have customers exceeding these limits including internal customers for demos, preventing them from creating new clusters within the subscription & region due to these scaling limits.  

N/A

Always.  

1. Scale up the number of image registry pods to hit the 100 / 5 minute List limit (50 replicas, or enough clusters within a given subscription & region)
2. Attempt to create a new cluster
3. Cluster installation may fail due to image-registry cluster operator never going healthy, or the installer not being able to generate a storage account key for the bootstrap node to fetch its ignition config.  

storage.AccountsClient#ListAccountSAS: Failure responding to request: StatusCode=429 -- Original Error: autorest/azure: Service returned an error. Status=429 Code="TooManyRequests" Message="The request is being throttled as the limit has been reached for operation type - Read_ObservationWindow_00:05:00. For more information, see - https://aka.ms/srpthrottlinglimits"

Cluster installs successfully

Raising this as a bug since this issue will be persistent across all cluster installations should one exceed the threshold.  It will also impact the image-registry pod health.