Azure Kubernetes Service (AKS) node auto-drain
Node auto-drain helps you protect your node workloads from disruptions when scheduled events occur on the underlying virtual machines (VMs) in any of your node pools. When certain node events happen, node auto-drain attempts a cordon and drain of the affected node so the workloads can be rescheduled safely. An example of when node auto-drain might occur is when scheduled events on a spot node pool cause a preempt node event. The spot node with the taint "kubernetes.azure.com/scalesetpriority: spot" may receive a taint with "remediator.kubernetes.azure.com/unschedulable" when a scheduled event occurs on that node.
Note
Node auto-drain is a best effort service and can't be guaranteed to operate perfectly in all scenarios.
The following table shows the node events for AKS node auto-drain and describes their associated actions:
| Event | Description | Action |
|---|---|---|
| Freeze | The underlying virtual machine (VM) is scheduled to pause for a few seconds. CPU and network connectivity may be suspended, but there's no impact on memory or open files. | No action. |
| Reboot | The VM is scheduled for reboot. The VM's non-persistent memory is lost. | No action. |
| Redeploy | The VM is scheduled to move to another node. The VM's ephemeral disks are lost. | Cordon and drain. |
| Preempt | The spot VM is being deleted. The VM's ephemeral disks are lost. | Cordon and drain |
| Terminate | The VM is scheduled for deletion. | Cordon and drain. |
Use availability zones to increase high availability with your AKS cluster workloads.