k8sリソースをグループ化する


### 複数のk8sリソースを1つのyamlにまとめたい
k8sのリソースは `---` で区切ることで1つのyamlにグループ化する事ができる
例えばdatadog-agentをデプロイするために必要なリソースをまるっと書くとこうなる

```yaml

kind: Namespace
apiVersion: v1
metadata:
  name: datadog
---
kind: ServiceAccount
apiVersion: v1
metadata:
  name: datadog-agent
  namespace: datadog
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: datadog-agent
rules:
- apiGroups:
  - ""
  resources:
  - services
  - events
  - endpoints
  - pods
  - nodes
  - componentstatuses
  verbs:
  - get
  - list
  - watch
- apiGroups: ["quota.openshift.io"]
  resources:
  - clusterresourcequotas
  verbs:
  - get
  - list
- apiGroups:
  - ""
  resources:
  - configmaps
  resourceNames:
  - datadogtoken             # Kubernetes event collection state
  - datadog-leader-election  # Leader election token
  verbs:
  - get
  - update
- apiGroups:  # To create the leader election token
  - ""
  resources:
  - configmaps
  verbs:
  - create
- nonResourceURLs:
  - "/version"
  - "/healthz"
  - "/metrics"
  verbs:
  - get
- apiGroups:  # Kubelet connectivity
  - ""
  resources:
  - nodes/metrics
  - nodes/spec
  - nodes/proxy
  verbs:
  - get
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: datadog-agent
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: datadog-agent
subjects:
- kind: ServiceAccount
  name: datadog-agent
  namespace: datadog
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: datadog-agent
  namespace: datadog
spec:
  selector:
    matchLabels:
      app: datadog-agent
  template:
    metadata:
      labels:
        app: datadog-agent
      name: datadog-agent
    spec:
      serviceAccountName: datadog-agent
      containers:
      - image: datadog/agent:latest
        imagePullPolicy: Always
        name: datadog-agent
        ports:
          - containerPort: 8125
            # Custom metrics via DogStatsD - uncomment this section to enable custom metrics collection
            # hostPort: 8125
            name: dogstatsdport
            protocol: UDP
          - containerPort: 8126
            # Trace Collection (APM) - uncomment this section to enable APM
            # hostPort: 8126
            name: traceport
            protocol: TCP
        env:
          - name: DD_API_KEY
            valueFrom:
              secretKeyRef:
                name: datadog-secret
                key: api-key
          - name: DD_COLLECT_KUBERNETES_EVENTS
            value: "true"
          - name: DD_LEADER_ELECTION
            value: "true"
          - name: KUBERNETES
            value: "true"
          - name: DD_KUBERNETES_KUBELET_HOST
            valueFrom:
              fieldRef:
                fieldPath: status.hostIP
          - name: DD_APM_ENABLED
            value: "true"
        resources:
          requests:
            memory: "256Mi"
            cpu: "200m"
          limits:
            memory: "256Mi"
            cpu: "200m"
        volumeMounts:
          - name: dockersocket
            mountPath: /var/run/docker.sock
          - name: procdir
            mountPath: /host/proc
            readOnly: true
          - name: cgroups
            mountPath: /host/sys/fs/cgroup
            readOnly: true
        livenessProbe:
          exec:
            command:
            - ./probe.sh
          initialDelaySeconds: 15
          periodSeconds: 5
      volumes:
        - hostPath:
            path: /var/run/docker.sock
          name: dockersocket
        - hostPath:
            path: /proc
          name: procdir
        - hostPath:
            path: /sys/fs/cgroup
          name: cgroups
```

### リソースの順番に気をつける

リソースは、ファイルに記載されている順序で作成されるので書く順番に気をつける

例えばNamespaceより先にDeploymentを書くと

```yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx
  namespace: nginx
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        ports:
        - containerPort: 80
---
kind: Namespace
apiVersion: v1
metadata:
  name: nginx
```

Namespaceが見つからないと怒られるが

```sh

$ kubectl apply -f nginx.yaml 
namespace/nginx created
Error from server (NotFound): error when creating "test.yaml": namespaces "nginx" not found
```

Namespaceを先に書くと

```yaml
kind: Namespace
apiVersion: v1
metadata:
  name: nginx
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: nginx
  namespace: nginx
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        ports:
        - containerPort: 80
```

怒られない

```sh
$ kubectl apply -f nginx.yaml 
namespace/nginx created
deployment.extensions/nginx created
```

docs
https://kubernetes.io/docs/concepts/cluster-administration/manage-deployment/#organizing-resource-configurations