Azure throttling

Azure constantly monitors incoming requests from the SolarWinds Platform and throttles VMs, as necessary, to control the consumption of resources so it can continue to function even when increased demand places an extreme load on resources.

For each subscription and tenant across all regions, the Azure Resource Manager limits read requests to 12,000 per hour and write requests to 1,200 per hour for each VM. For each region, Azure limits read requests to 25,000 per hour but it may be hard to predict how often that limit will be reached in a region.

The number of requests is scoped to either your subscription or tenant. If you have multiple, concurrent applications making requests in your subscription, those requests are added together to determine the number of remaining requests.

When read requests from the SolarWinds Platform reach the limits, Azure sends HTTP status code 429 and triggered alerts appear in the SolarWinds Platform Web Console. The status of a throttled VM switches to N/A — not available — until polling resumes.

For tips on reducing Azure throttling, click here.

The SolarWinds Platform checks every minute for throttled VMs and volumes. To prevent multiple alerts from flooding the alert list, the Azure throttling is applied for cloud account alert aggregates throttling events for VMs or volumes linked to an account into a single alert. An email notification indicates the number of affected VMs and volumes.

To always receive alerts per throttled VM and volume, disable the account level alert and enable the following alerts.

If multiple VMs and volumes incur throttling, the list of alerts can be extensive.

• Azure throttling is applied for VM: Disabled by default, this alert checks every minute to determine if throttling is applied to VM. Conditions check for the VM status of Unknown and throttling applied through Azure API calls.
  
• Azure throttling is applied for cloud volume: Disabled by default, this alert checks every minute to determine if throttling is applied to volumes. Conditions check for the attached volume status of Unknown and throttling applied through Azure API calls.

To create additional throttling alerts, copy an existing alert and customize it. See Manage cloud monitoring alerts.