Kubernetes 指定したラベルが付与されているNodeにPodをDeployする(yaml)

Kubernetes1.15でのお話

#ラベル付与
## 現状
```
[root@master1 ]# kubectl get node --show-labels
NAME     STATUS   ROLES    AGE     VERSION   LABELS
node1    Ready    <none>   43h     v1.15.2   (略)kubernetes.io/hostname=node1,kubernetes.io/os=linux
node2    Ready    <none>   2d21h   v1.15.2   (略)kubernetes.io/hostname=ops01,kubernetes.io/os=linux
```

## ラベル付与
```
# 例：kubectl label node "node名" node="ラベル名"
[root@master1 ]# kubectl label node node1 node=worker1
[root@master1 ]# kubectl label node node2 node=workerA
```

## ラベル付与確認
```
[root@master1 ]# kubectl get node --show-labels
NAME     STATUS   ROLES    AGE     VERSION   LABELS
node1    Ready    <none>   43h     v1.15.2   (略)kubernetes.io/hostname=node1,kubernetes.io/os=linux,node=worker1
node2    Ready    <none>   2d21h   v1.15.2   (略)kubernetes.io/hostname=ops01,kubernetes.io/os=linux,node=workerA
```

#Pod Deploy

##yaml編集

例としてCore DNSのPodをDeployする。
ソースは
https://raw.githubusercontent.com/coredns/deployment/master/kubernetes/coredns.yaml.sed

当環境の例なので、

```
kubernetes cluster.local 10.254.0.0/16
forward . /etc/resolv.conf
clusterIP: 10.254.0.2
```
あたりは環境によって異なると思われるので注意。
少し話題が逸れるが、
今回の場合はDNSのPodをDeployするNodeの/etc/resolv.confが
設定されていないと外への通信(コンテナ内→Google等)はできない。

```
[root@master1 k8s]# cat coredns.yaml 
apiVersion: v1
kind: ServiceAccount
metadata:
  name: coredns
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: system:coredns
rules:
- apiGroups:
  - ""
  resources:
  - endpoints
  - services
  - pods
  - namespaces
  verbs:
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - nodes
  verbs:
  - get
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: system:coredns
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:coredns
subjects:
- kind: ServiceAccount
  name: coredns
  namespace: kube-system
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system
data:
  Corefile: |
    .:53 {
        errors
        health
        ready
        kubernetes cluster.local 10.254.0.0/16 {
          pods insecure
          fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        forward . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: coredns
  namespace: kube-system
  labels:
    k8s-app: kube-dns
    kubernetes.io/name: "CoreDNS"
spec:
  replicas: 1
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1
  selector:
    matchLabels:
      k8s-app: kube-dns
  template:
    metadata:
      labels:
        k8s-app: kube-dns
    spec:
      hostNetwork: true
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: node
                operator: In
                values:
                - workerA 
#    spec:
      priorityClassName: system-cluster-critical
      serviceAccountName: coredns
      tolerations:
        - key: "CriticalAddonsOnly"
          operator: "Exists"
      nodeSelector:
        beta.kubernetes.io/os: linux
      containers:
      - name: coredns
        image: coredns/coredns:1.6.2
        imagePullPolicy: IfNotPresent
        resources:
          limits:
            memory: 170Mi
          requests:
            cpu: 100m
            memory: 70Mi
        args: [ "-conf", "/etc/coredns/Corefile" ]
        volumeMounts:
        - name: config-volume
          mountPath: /etc/coredns
          readOnly: true
        ports:
        - containerPort: 53
          name: dns
          protocol: UDP
        - containerPort: 53
          name: dns-tcp
          protocol: TCP
        - containerPort: 9153
          name: metrics
          protocol: TCP
        securityContext:
          allowPrivilegeEscalation: false
          capabilities:
            add:
            - NET_BIND_SERVICE
            drop:
            - all
          readOnlyRootFilesystem: true
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
            scheme: HTTP
          initialDelaySeconds: 60
          timeoutSeconds: 5
          successThreshold: 1
          failureThreshold: 5
        readinessProbe:
          httpGet:
            path: /ready
            port: 8181
            scheme: HTTP
      dnsPolicy: Default
      volumes:
        - name: config-volume
          configMap:
            name: coredns
            items:
            - key: Corefile
              path: Corefile
---
apiVersion: v1
kind: Service
metadata:
  name: kube-dns
  namespace: kube-system
  annotations:
    prometheus.io/port: "9153"
    prometheus.io/scrape: "true"
  labels:
    k8s-app: kube-dns
    kubernetes.io/cluster-service: "true"
    kubernetes.io/name: "CoreDNS"
spec:
  selector:
    k8s-app: kube-dns
  clusterIP: 10.254.0.2
  ports:
  - name: dns
    port: 53
    protocol: UDP
  - name: dns-tcp
    port: 53
    protocol: TCP
  - name: metrics
    port: 9153
    protocol: TCP

```



今回キモとなるのは上記Yaml内のDeployment部分の

```
    spec:
      hostNetwork: true
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: node
                operator: In
                values:
                - workerA

```
この部分。
valuesの項目をラベル名にする(当例だとworkerA)

## Yaml Deploy
 
```
#Deploy
[root@master1 ]# kubectl apply -f coredns.yaml


[root@master1 ]#  kubectl get pods -o wide --all-namespaces
NAMESPACE     NAME                                      READY   STATUS    RESTARTS   AGE     IP                NODE     NOMINATED NODE   READINESS GATES
default       nginx-ds-3dsxd                            1/1     Running   0          43h     192.168.   worker1    <none>           <none>
default       nginx-ds-dhrcs                            1/1     Running   0          43h     192.168.   workerA    <none>           <none>
kube-system   calico-kube-controllers-9859              1/1     Running   0          2d21h   192.168.   worker1    <none>           <none>
kube-system   coredns-c3546349-7dh1d                    1/1     Running   0          175m    192.168.   workerA    <none>           <none>


```