How do you distribute pods across different nodes in Kubernetes?

There are several approaches to distribute pods across different nodes in Kubernetes:

1. nodeSelector — a simple way to specify on which nodes a pod can run, using node labels.

2. affinity/anti-affinity — a more flexible mechanism that allows setting rules for preferences and obligations regarding pod placement relative to nodes or other pods.

3. PodTopologySpread — controls the distribution of pods across topology domains (e.g., nodes) to avoid concentration.

4. Taints and Tolerations — allow marking nodes and permitting pods to run only with the corresponding tolerations.

Example of using anti-affinity to spread pods across different nodes:

apiVersion: v1
kind: Pod
metadata:
  name: example-pod
spec:
  affinity:
    podAntiAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - key: app
            operator: In
            values:
            - myapp
        topologyKey: "kubernetes.io/hostname"
  containers:
  - name: mycontainer
    image: myimage

This rule prevents pods with the label app: myapp from running on the same node, ensuring their distribution.