Taint and Toleration
A mechanism in Kubernetes used to control which pods can be scheduled on specific nodes based on node conditions.
Description
In Kubernetes, 'Taint and Toleration' is a powerful mechanism that allows cluster operators to control pod placement on nodes. A 'taint' is a property that can be applied to a node, which prevents pods from being scheduled on that node unless they have a matching 'toleration'. Taints and tolerations are often used to manage workloads in a way that ensures that only certain pods can run on particular nodes, typically to handle special requirements or conditions. For instance, if a node has limited resources or is dedicated to a specific environment (like a testing environment), operators can taint that node. Tolerations allow pods to tolerate these taints, enabling them to be scheduled on those nodes. This mechanism is particularly useful for managing high availability and resource allocation, ensuring that critical applications have the resources they need while preventing less critical workloads from interfering.
Examples
- A node dedicated to GPU workloads is tainted with 'special-resource=true:NoSchedule', allowing only workloads that have a matching toleration to be scheduled on it.
- A testing node might be tainted with 'env=test:NoExecute', ensuring that only pods with the required toleration can run on it, isolating test workloads from production.
Additional Information
- Taints can be applied to nodes using the command 'kubectl taint nodes
key=value:effect'. - Tolerations can be defined in a pod's specification, allowing it to 'tolerate' specific node taints.