Скачать или смотреть DevOps SRE Interview Question 121 Kubernetes Pod Scheduling Factors

Hello everyone!

Today, we're continuing our exploration of the top 15 key topics for DevOps interviews, based on my research from LinkedIn job postings. However, due to high demand and feedback from YouTube comments, we'll be focusing on Kubernetes and Terraform for a while.

In this session, we'll delve into Kubernetes, specifically answering the question: How does Kubernetes handle pod scheduling, and what factors influence this process?

Imagine a Kubernetes cluster with multiple nodes, where nodes are essentially virtual machines. When a pod is ready to be placed on one of these nodes, how does Kubernetes decide where it should go? This decision is managed by Kubernetes' scheduler, which takes into account several factors. Let's examine some of the key criteria:

1. **Resource Requests and Limits**: Containers can define CPU and memory requirements. If a node doesn't meet these requirements, the pod won't be scheduled there.

2. **Node Affinity and Pod Affinity**: Node affinity ensures that pods are scheduled on nodes with specific tags, like separating staging from production. Pod affinity, on the other hand, ensures that certain pods (e.g., a database and a front-end server) are co-located on the same node.

3. **Taints and Tolerations**: Taints prevent certain pods from being scheduled on a node, while tolerations can override taints, allowing the pod to be scheduled. For instance, no user pods are scheduled on master nodes by default.

4. **Node Selectors**: This allows you to specify, in the pod’s YAML file, that it should run on a particular node.

5. **Priority and Preemption**: Pods with higher priority (e.g., database pods) can take precedence over lower-priority pods. Preemption can even force running pods to be evicted to make room for higher-priority pods.

6. **Topology Awareness**: You can configure pods to be scheduled in specific zones or regions, helping optimize latency and resource utilization.

7. **Node Conditions**: The health status of nodes also influences scheduling. Unhealthy nodes won't receive new pods until they recover.

In an interview, you won’t need to cover every detail, but remember a few key points to demonstrate your understanding.

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