Draino automatically drains Kubernetes nodes based on labels and node conditions. Nodes that match all of the supplied labels and any of the supplied node conditions will be cordoned immediately and drained after a configurable drain-buffer time.

Draino is intended for use alongside the Kubernetes Node Problem Detector and Cluster Autoscaler. The Node Problem Detector can set a node condition when it detects something wrong with a node – for instance by watching node logs or running a script. The Cluster Autoscaler can be configured to delete nodes that are underutilised. Adding Draino to the mix enables autoremediation:

  1. The Node Problem Detector detects a permanent node problem and sets the corresponding node condition.
  2. Draino notices the node condition. It immediately cordons the node to prevent new pods being scheduled there, and schedules a drain of the node.
  3. Once the node has been drained the Cluster Autoscaler will consider it underutilised. It will be eligible for scale down (i.e. termination) by the Autoscaler after a configurable period of time.

There is currently no Helm chart available for Draino which is a shame. However, it should be reasonably easy to create one using the example deployment manifest. It may be a good idea to include the Node Problem Detector daemonset as part of the package since no Helm chart exists for that either.

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