How to achieve 1 node = 1 pod in Kubernetes

Question

I have 5 nodes in a cluster (Test). I have labeled them to the following:

Nodes:

• namespace=A
• namespace=A
• namespace=B
• namespace=B
• namespace=C

I applied taints and tolerations, nodeAffinity and podAntiAffinity. Our nodes is auto scale enabled. However, our nodes weren't scaling up, all the pods are going in 1 node. I have read in this link Kubernetes: Evenly distribute the replicas across the cluster, that using podAntiAffinity, node Affinity, taints and tolerations do not guarantee this requirement. Our requirement is, 1 pod should be deployed evenly on nodes and should scale up accordingly.

What am I missing?

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: prometheus
  labels:
    app: prometheus
spec:
  serviceName: "prometheus"
  selector:
    matchLabels:
      name: prometheus
  template:
    metadata:
      labels:
        name: prometheus
        app: prometheus
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: namespace
                operator: In
                values:
                - A
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - podAffinityTerm:
              labelSelector:
                matchExpressions:
                - key: app
                  operator: In
                  values:
                  - prometheus
              topologyKey: kubernetes.io/hostname
            weight: 100
      containers:
      - name: prometheus
        image: quay.io/prometheus/prometheus:v2.6.0
        resources:
          limits:
            memory: 200Mi
          requests:
            cpu: 100m
            memory: 200Mi
      terminationGracePeriodSeconds: 30
      tolerations:
      - key: namespace
        operator: Equal
        value: A

Answer 1

Did you try nodeSelector which will schedule the pod on the node that you attached the label to?

  nodeSelector:
    namespace: A