CKA 模拟真题 Killer.sh | Question 12 | Deployment on all Nodes

Use context: kubectl config use-context k8s-c1-H

Use Namespace project-tiger for the following. Create a Deployment named deploy-important with label id=very-important (the Pods should also have this label) and 3 replicas. It should contain two containers, the first named container1 with image nginx:1.17.6-alpine and the second one named container2 with image kubernetes/pause .

There should be only ever one Pod of that Deployment running on one worker node. We have two worker nodes: cluster1-node1 and cluster1-node2 . Because the Deployment has three replicas the result should be that on both nodes one Pod is running. The third Pod won’t be scheduled, unless a new worker node will be added.

In a way we kind of simulate the behaviour of a DaemonSet here, but using a Deployment and a fixed number of replicas.

---

译文

使用命名空间 project-tiger 进行以下工作。

创建一个名为deploy-important 的部署，标签 id=very-important （Pod也应该有这个标签）和3个副本。

它应该包含两个容器，第一个名为container1 ，镜像为 nginx:1.17.6-alpine ，第二个名为 container2 ，镜像为 kubernetes/pause 。

在一个工作节点上应该只有 一个 部署的Pod在运行。我们有两个工作节点： cluster1-node1 和 cluster1-node2 。
因为该部署有三个副本，结果应该是两个节点上都有一个Pod在运行。第三个Pod不会被安排，除非有一个新的工作节点被添加。

在某种程度上，我们在这里模拟了DaemonSet的行为，但使用了一个部署和固定数量的副本

---

解答

有两种方式，一种使用 podAntiAffinity ，一种使用 topologySpreadConstraint

PodAntiAffinity

k -n project-tiger create deployment \
--image=nginx:1.17.6-alpine deploy-important $do > 12.yaml

vim 12.yaml

12.vim

# 12.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    id: very-important                  # change
  name: deploy-important
  namespace: project-tiger              # important
spec:
  replicas: 3                           # change
  selector:
    matchLabels:
      id: very-important                # change
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        id: very-important              # change
    spec:
      containers:
      - image: nginx:1.17.6-alpine
        name: container1                # change
        resources: {}
      - image: kubernetes/pause         # add
        name: container2                # add
      affinity:                                             # add
        podAntiAffinity:                                    # add
          requiredDuringSchedulingIgnoredDuringExecution:   # add
          - labelSelector:                                  # add
              matchExpressions:                             # add
              - key: id                                     # add
                operator: In                                # add
                values:                                     # add
                - very-important                            # add
            topologyKey: kubernetes.io/hostname             # add
status: {}

TopologySpreadConstraints

# 12.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    id: very-important                  # change
  name: deploy-important
  namespace: project-tiger              # important
spec:
  replicas: 3                           # change
  selector:
    matchLabels:
      id: very-important                # change
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        id: very-important              # change
    spec:
      containers:
      - image: nginx:1.17.6-alpine
        name: container1                # change
        resources: {}
      - image: kubernetes/pause         # add
        name: container2                # add
      topologySpreadConstraints:                 # add
      - maxSkew: 1                               # add
        topologyKey: kubernetes.io/hostname      # add
        whenUnsatisfiable: DoNotSchedule         # add
        labelSelector:                           # add
          matchLabels:                           # add
            id: very-important                   # add
status: {}

创建对应的deployment

k -f 12.yaml create

我们检查部署状态，它显示2/3的准备数量。其中有一个没有被调度

k -n project-tiger get deploy -l id=very-important
k -n project-tiger get pod -o wide -l id=very-important