PodPreset

PodPreset 用来给指定标签的 Pod 注入额外的信息，如环境变量、存储卷等。这样，Pod 模板就不需要为每个 Pod 都显式设置重复的信息。
当然，你也可以给 Pod 增加注解 podpreset.admission.kubernetes.io/exclude: "true" 来避免它们被 PodPreset 修改。
API 版本对照表
Kubernetes 版本
API 版本
默认开启
v1.6+
settings.k8s.io/v1alpha1
否
开启 PodPreset
开启 API kube-apiserver --runtime-config=settings.k8s.io/v1alpha1=true
开启准入控制 --enable-admission-plugins=..,PodPreset
PodPreset 示例
增加环境变量和存储卷的 PodPreset
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kind: PodPreset
2
apiVersion: settings.k8s.io/v1alpha1
3
metadata:
4
  name: allow-database
5
  namespace: myns
6
spec:
7
  selector:
8
    matchLabels:
9
      role: frontend
10
  env:
11
    - name: DB_PORT
12
      value: "6379"
13
  volumeMounts:
14
    - mountPath: /cache
15
      name: cache-volume
16
  volumes:
17
    - name: cache-volume
18
      emptyDir: {}
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用户提交 Pod
1
apiVersion: v1
2
kind: Pod
3
metadata:
4
  name: website
5
  labels:
6
    app: website
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    role: frontend
8
spec:
9
  containers:
10
    - name: website
11
      image: ecorp/website
12
      ports:
13
        - containerPort: 80
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经过准入控制 PodPreset 后，Pod 会自动增加环境变量和存储卷
1
apiVersion: v1
2
kind: Pod
3
metadata:
4
  name: website
5
  labels:
6
    app: website
7
    role: frontend
8
  annotations:
9
    podpreset.admission.kubernetes.io/allow-database: "resource version"
10
spec:
11
  containers:
12
    - name: website
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      image: ecorp/website
14
      volumeMounts:
15
        - mountPath: /cache
16
          name: cache-volume
17
      ports:
18
        - containerPort: 80
19
      env:
20
        - name: DB_PORT
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          value: "6379"
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  volumes:
23
    - name: cache-volume
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      emptyDir: {}
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ConfigMap 示例
ConfigMap
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apiVersion: v1
2
kind: ConfigMap
3
metadata:
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  name: etcd-env-config
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data:
6
  number_of_members: "1"
7
  initial_cluster_state: new
8
  initial_cluster_token: DUMMY_ETCD_INITIAL_CLUSTER_TOKEN
9
  discovery_token: DUMMY_ETCD_DISCOVERY_TOKEN
10
  discovery_url: http://etcd_discovery:2379
11
  etcdctl_peers: http://etcd:2379
12
  duplicate_key: FROM_CONFIG_MAP
13
  REPLACE_ME: "a value"
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PodPreset
1
kind: PodPreset
2
apiVersion: settings.k8s.io/v1alpha1
3
metadata:
4
  name: allow-database
5
  namespace: myns
6
spec:
7
  selector:
8
    matchLabels:
9
      role: frontend
10
  env:
11
    - name: DB_PORT
12
      value: 6379
13
    - name: duplicate_key
14
      value: FROM_ENV
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    - name: expansion
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      value: $(REPLACE_ME)
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  envFrom:
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    - configMapRef:
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        name: etcd-env-config
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  volumeMounts:
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    - mountPath: /cache
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      name: cache-volume
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    - mountPath: /etc/app/config.json
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      readOnly: true
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      name: secret-volume
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  volumes:
27
    - name: cache-volume
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      emptyDir: {}
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    - name: secret-volume
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      secretName: config-details
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用户提交的 Pod
1
apiVersion: v1
2
kind: Pod
3
metadata:
4
  name: website
5
  labels:
6
    app: website
7
    role: frontend
8
spec:
9
  containers:
10
    - name: website
11
      image: ecorp/website
12
      ports:
13
        - containerPort: 80
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经过准入控制 PodPreset 后，Pod 会自动增加 ConfigMap 环境变量
1
apiVersion: v1
2
kind: Pod
3
metadata:
4
  name: website
5
  labels:
6
    app: website
7
    role: frontend
8
  annotations:
9
    podpreset.admission.kubernetes.io/allow-database: "resource version"
10
spec:
11
  containers:
12
    - name: website
13
      image: ecorp/website
14
      volumeMounts:
15
        - mountPath: /cache
16
          name: cache-volume
17
        - mountPath: /etc/app/config.json
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          readOnly: true
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          name: secret-volume
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      ports:
21
        - containerPort: 80
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      env:
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        - name: DB_PORT
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          value: "6379"
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        - name: duplicate_key
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          value: FROM_ENV
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        - name: expansion
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          value: $(REPLACE_ME)
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      envFrom:
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        - configMapRef:
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          name: etcd-env-config
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  volumes:
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    - name: cache-volume
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      emptyDir: {}
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    - name: secret-volume
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      secretName: config-details
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修改 Pod 时区示例
下面的示例会把带有标签 tz: shanghai的所有Pod都自动改成上海时区：
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kind: PodPreset
2
apiVersion: settings.k8s.io/v1alpha1
3
metadata:
4
  name: tz-shanghai
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  namespace: default
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spec:
7
  selector:
8
    matchLabels:
9
      tz: shanghai
10
  volumeMounts:
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    - mountPath: /etc/localtime
12
      name: tz-config
13
  volumes:
14
    - name: tz-config
15
      hostPath:
16
        path: /usr/share/zoneinfo/Asia/Shanghai
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