How Do I Evenly Distribute Multiple Pods to Each Node?

The kube-scheduler component in Kubernetes is responsible pod scheduling. For each newly created pod or other unscheduled pods, kube-scheduler selects an optimal node from them to run on. kube-scheduler selects a node for a pod in a 2-step operation: filtering and scoring. In the filtering step, all nodes where it is feasible to schedule the pod are filtered out. In the scoring step, kube-scheduler ranks the remaining nodes to choose the most suitable pod placement. Finally, kube-scheduler schedules the pod to the node with the highest score. If there is more than one node with the equal scores, kube-scheduler selects one of them at random.

BalancedResourceAllocation is only one of the scoring priorities. Other scoring items may also cause uneven distribution. For details about scheduling, see Kubernetes Scheduler and Scheduling Policies.

You can configure pod anti-affinity policies to evenly distribute pods onto different nodes.

Example:

kind: Deployment
apiVersion: apps/v1
metadata:
  name: nginx
  namespace: default
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: container-0
          image: nginx:alpine
          resources:
            limits:
              cpu: 250m
              memory: 512Mi
            requests:
              cpu: 250m
              memory: 512Mi
      affinity:
        podAntiAffinity:                   # Workload anti-affinity
          preferredDuringSchedulingIgnoredDuringExecution:    # Ensure that the following conditions are met:
            - weight: 100 # Priority that can be configured when the best-effort policy is used. The value ranges from 1 to 100. A larger value indicates a higher priority.
              podAffinityTerm:
                labelSelector:                       # Select the label of the pod, which is anti-affinity with the workload.
                  matchExpressions:
                    - key: app
                      operator: In
                      values:
                        - nginx
                namespaces:
                  - default
                topologyKey: kubernetes.io/hostname     # It takes effect on the node.
      imagePullSecrets:
        - name: default-secret