Modifying Kubernetes objects

You can delegate Kubernetes object manipulation to the shell-operator.

To do this, you have to write one or more JSON or YAML documents describing operation type and its parameters to a file. List of possible operations and corresponding JSON specifications can be found below.

The path to the file is found in the $KUBERNETES_PATCH_PATH environment variable.

Operations

Create

operation — specifies an operation’s type.
- CreateOrUpdate — accept a Kubernetes object. It retrieves an object, and if it already exists, computes a JSON Merge Patch and applies it (will not update .status field). If it does not exist, we create the object.
- Create — will fail if an object already exists
- CreateIfNotExists — create an object if such an object does not already exist by namespace/name.
object — full object specification including “apiVersion”, “kind” and all necessary metadata. Can be a normal JSON or YAML object or a stringified JSON or YAML object.

Example

{
  "operation": "CreateOrUpdate",
  "object": {
    "apiVersion": "apps/v1",
    "kind": "DaemonSet",
    "metadata": {
      "name": "flannel",
      "namespace": "d8-flannel"
    },
    "spec": {
      "selector": {
        "matchLabels": {
          "app": "flannel"
        }
      },
      "template": {
        "metadata": {
          "labels": {
            "app": "flannel",
            "tier": "node"
          }
        },
        "spec": {
          "containers": [
            {
              "args": [
                "--ip-masq",
                "--kube-subnet-mgr"
              ],
              "image": "flannel:v0.11",
              "name": "kube-flannel",
              "securityContext": {
                "privileged": true
              }
            }
          ],
          "hostNetwork": true,
          "imagePullSecrets": [
            {
              "name": "registry"
            }
          ],
          "terminationGracePeriodSeconds": 5
        }
      },
      "updateStrategy": {
        "type": "RollingUpdate"
      }
    }
  }
}

operation: Create
object:
  apiVersion: v1
  kind: ConfigMap
  metadata:
    namespace: default
    name: testcm
  data: ...

operation: Create
object: |
  {"apiVersion":"v1", "kind":"ConfigMap",
   "metadata":{"namespace":"default","name":"testcm"},
   "data":{"foo": "bar"}}

Delete

operation — specifies an operation’s type. Deletion types map directly to Kubernetes DELETE’s propagationPolicy.
- Delete — foreground deletion. Hook will block the queue until the referenced object and all its descendants are deleted.
- DeleteInBackground — will delete the referenced object immediately. All its descendants will be removed by Kubernetes’ garbage collector.
- DeleteNonCascading — will delete the referenced object immediately, and orphan all its descendants.
apiVersion — optional field that specifies object’s apiVersion. If not present, we’ll use preferred apiVersion for the given kind.
kind — object’s Kind.
namespace — object’s namespace. If empty, implies operation on a cluster-level resource.
name — object’s name.
subresource — a subresource name if subresource is to be transformed. For example, status.

Example

{
  "operation": "Delete",
  "kind": "Pod",
  "namespace": "default",
  "name": "nginx"
}

Patch

Use JQPatch for almost everything. Consider using MergePatch or JSONPatch if you are attempting to modify rapidly changing object, for example status field with many concurrent changes (and incrementing resourceVersion).

Be careful, when updating a .status field. If a /status subresource is enabled on a resource, it’ll ignore updates to the .status field if you haven’t specified subresource: status in the operation spec. More info here.

JQPatch

operation — specifies an operation’s type.
apiVersion — optional field that specifies object’s apiVersion. If not present, we’ll use preferred apiVersion for the given kind.
kind — object’s Kind.
namespace — object’s Namespace. If empty, implies operation on a Cluster-level resource.
name — object’s name.
jqFilter — describes transformations to perform on an object.
subresource — a subresource name if subresource is to be transformed. For example, status.

Example

{
  "operation": "JQPatch",
  "kind": "Deployment",
  "namespace": "default",
  "name": "nginx",
  "jqFilter": ".spec.replicas = 1"
}

MergePatch

operation — specifies an operation’s type.
apiVersion — optional field that specifies object’s apiVersion. If not present, we’ll use preferred apiVersion for the given kind.
kind — object’s Kind.
namespace — object’s Namespace. If empty, implies operation on a Cluster-level resource.
name — object’s name.
mergePatch — describes transformations to perform on an object. Can be a normal JSON or YAML object or a stringified JSON or YAML object.
subresource — e.g., status.
ignoreMissingObject — set to true to ignore error when patching non existent object.

Example

{
  "operation": "MergePatch",
  "kind": "Deployment",
  "namespace": "default",
  "name": "nginx",
  "mergePatch": {
    "spec": {
      "replicas": 1
    }
  }
}

operation: MergePatch
kind: Deployment
namespace: default
name: nginx
ignoreMissingObject: true
mergePatch: |
  spec:
    replicas: 1

JSONPatch

operation — specifies an operation’s type.
apiVersion — optional field that specifies object’s apiVersion. If not present, we’ll use preferred apiVersion for the given kind.
kind — object’s Kind.
namespace — object’s Namespace. If empty, implies operation on a Cluster-level resource.
name — object’s name.
jsonPatch — describes transformations to perform on an object. Can be a normal JSON or YAML array or a stringified JSON or YAML array.
subresource — a subresource name if subresource is to be transformed. For example, status.
ignoreMissingObject — set to true to ignore error when patching non existent object.

Example

{
  "operation": "JSONPatch",
  "kind": "Deployment",
  "namespace": "default",
  "name": "nginx",
  "jsonPatch": [
    {"op": "replace", "path":  "/spec/replicas", "value":  1}
  ]
}

{
  "operation": "JSONPatch",
  "kind": "Deployment",
  "namespace": "default",
  "name": "nginx",
  "jsonPatch": "[
    {\"op\": \"replace\", \"path\":  \"/spec/replicas\", \"value\":  1}
  ]"
}

Shell-operator