Rethinking Node Drains: A Webhook Based Approach to Graceful Pod Removal

Running stateful applications in Kubernetes presents challenges during node maintenance, as pod evictions can disrupt services. To address this, the Eviction Reschedule Hook, an open-source project, uses Kubernetes Admission Controllers to manage and safeguard operator-managed pods by intercepting and rejecting eviction requests while alerting the operator to safely reschedule the pod. This project aims to ensure service availability and reduce disruptions, particularly during node drains, which are necessary for operations like maintenance. It is implemented as a Kubernetes admission controller and works alongside Operators, such as the Couchbase Autonomous Operator, to automate pod rescheduling without affecting the standard kubectl drain command. By leveraging Kubernetes webhooks and a validating admission controller, the hook checks eviction requests and uses annotations to signal the need for rescheduling, ensuring pods are moved safely without impacting the application. The project allows for community contributions and is designed to be flexible, supporting various operator-managed stateful applications beyond its initial Couchbase focus.

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