OpenShift- Taint & Tolerations

In OpenShift, taints and tolerations are mechanisms used to influence the scheduling of pods onto nodes within a cluster. They help control how pods are placed on nodes based on specific criteria.

Taints:

What is a Taint?

• A taint is a property applied to a node that repels certain pods.
• It represents a condition on a node that may affect whether a pod is scheduled on that node.

Example Taint:

• A node may be tainted to indicate that it shouldn’t accept workloads unless they have a specific toleration.

$ oc adm taint nodes <node-name> key=value:effect

--> <node-name> is the name of the node.
--> key=value is the taint key-value pair.
--> effect can be "NoSchedule" (default), "PreferNoSchedule," or "NoExecute."

Tolerations:

What is a Toleration?

• A toleration is a pod specification that allows a pod to be scheduled onto a node with a matching taint.
• It essentially tells the scheduler that the pod can tolerate nodes with specific taints.

Example Toleration in Pod YAML:

tolerations:
- key: "key"
  operator: "Equal"
  value: "value"
  effect: "NoSchedule"

** 
This toleration means the pod tolerates nodes with a taint of key "key," value "value," and effect "NoSchedule."