Understanding Taints and Tolerations in Kubernetes

In Kubernetes, taints and tolerations are used to control which nodes can accept which pods, helping you to schedule workloads more efficiently.

• Taints:

  Taints are applied to nodes.They mark a node so that it won’t accept any pods unless those pods have a matching toleration. Taints prevent pods from being scheduled onto nodes unless the pod “tolerates” the taint. Think of a taint like a “No Entry” sign for pods unless they have special permission to enter (which is given through a toleration).

  The effect can be one of the following below:

  1. NoSchedule: Pods will not be scheduled on the node unless they have a matching toleration.

  2. PreferNoSchedule: Kubernetes tries to avoid scheduling pods on the node, but it's not guaranteed.

  3. NoExecute: Existing pods on the node will be evicted if they don't have a matching toleration.

Example:

kubectl taint node node01 key=value:NoSchedule

This will taint node1, that means no pod can be scheduled on node1 unless it has a matching toleration.

• Tolerations:

  Tolerations are applied to pods. They allow the pod to be scheduled on nodes with matching taints. Think of tolerations as the pod’s “special permission” to enter nodes that have a taint.

  Example of a toleration in a pod YAML:

  

  This toleration allows the pod to be scheduled on nodes that have the key1=value1:NoSchedule taint.

Best practices:

• Use taints and tolerations to manage node affinity and pod scheduling.

• Document taints and tolerations in your cluster for better understanding.

• Monitor node conditions and adjust taints accordingly.