Scale Kubernetes deployments via API

Question

I would like to scale (up and down) deployment from PODs. In other words, how PODs in the namespace will send a Kubernetes API call in order to scale the deployment?

I have created a role and assign it to a service account with the following privileges in order to send API calls:

apiVersion: v1
kind: ServiceAccount
metadata:
  creationTimestamp: "2019-05-19T18:52:09Z"
  name: {name}-sa
  namespace: {name}
  resourceVersion: "11378025"
  selfLink: /api/v1/namespaces/{name}/serviceaccounts/{name}-sa
  uid: 34606554-7a67-11e9-8e78-c6f4a9a0006a
secrets:
- name: {name}-sa-token-mgk5z



apiVersion: v1
items:
- apiVersion: rbac.authorization.k8s.io/v1
  kind: Role
  metadata:
    creationTimestamp: "2019-05-17T13:21:09Z"
    name: {name}-{name}-api-role
    namespace: {name}
    resourceVersion: "10985868"
    selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/{name}/roles/{name}-{name}-api-role
    uid: a298e71a-78a6-11e9-b54a-c6f4a9a00070
  rules:
  - apiGroups:
    - extensions
    - apps
    resources:
    - deployments
    verbs:
    - get
    - list
    - watch
    - create
    - update
    - patch
    - delete
- apiVersion: rbac.authorization.k8s.io/v1
  kind: RoleBinding
  metadata:
    creationTimestamp: "2019-05-17T13:45:46Z"
    name: {name}-{name}-api-rolebind
    namespace: {name}
    resourceVersion: "11378111"
    selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/{name}/rolebindings/{name}-{name}-api-rolebind
    uid: 12812ea7-78aa-11e9-89ae-c6f4a9a00064
  roleRef:
    apiGroup: rbac.authorization.k8s.io
    kind: Role
    name: {name}-{name}-api-role
  subjects:
  - kind: ServiceAccount
    name: {name}-sa
    namespace: {name}
kind: List
metadata:
  resourceVersion: ""
  selfLink: ""

I can retrieve the deployment with the following command, but I cannot find how to scale it.

https://$KUBERNETES_SERVICE_HOST:$KUBERNETES_PORT_443_TCP_PORT/apis/apps/v1/namespaces/{name}/deployments/{name}

I tried the following command in order to scale it, but failed:

curl --cacert /var/run/secrets/kubernetes.io/serviceaccount/ca.crt -H "Authorization: Bearer $(cat /var/run/secrets/kubernetes.io/serviceaccount/token)"  -X PUT  -d '[{ \
    "op":"replace", \
    "path":"/spec/replicas", \
    "value": "2" \
  }]'
 https://$KUBERNETES_SERVICE_HOST:$KUBERNETES_PORT_443_TCP_PORT/apis/apps/v1/namespaces/{name}/deployments/{name}

{
  "kind": "Status",
  "apiVersion": "v1",
  "metadata": {

  },
  "status": "Failure",
  "message": "deployments.apps \"{name}\" is forbidden: User \"system:serviceaccount:{name}:default\" cannot  resource \"deployments\" in API group \"apps\" in the namespace \"{name}\"",
  "reason": "Forbidden",
  "details": {
    "name": "{name}",
    "group": "apps",
    "kind": "deployments"
  },
  "code": 403

Answer 1

Using Kubernetes v1.16.13 on GKE.

I found that If you give patch permission for deployments/scale resource, you can do PATCH /apis/apps/v1/namespaces/default/deployments/{name}/scale.

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: {name}
rules:
- apiGroups: ["apps"]
  resources: ["deployments/scale"]
  verbs: ["patch"]