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Apply Existing Policies & Policy Logic

This page explains how to use existing policy logic and how to apply/enforce it in your cluster. If you are interested in writing (and potentially publishing) your own policy logic, read the writing policies and policy logic guide.

Existing policy logic comes in three forms:

  1. JsPolicy YAML files ready to be applied with kubectl apply -f policy.yaml
  2. JsPolicy + JsPolicyBundle YAML files usable with kubectl apply -f policy.bundle.yaml -f policy.yaml
  3. npm packages that export policy logic as functions that can be called in your own, custom JsPolicy objects


Before you apply a 3rd-party policy to your cluster, make sure that:

Policies are very powerful and can block/deny kubectl requests for example, so make sure you know what you are doing before applying a policy.

JsPolicy YAML files#

If someone shares a standalone JsPolicy object as a YAML file with you (or you created the file yourself), then you will likely find the spec.javascript field showing some JavaScript code embedded inside the YAML. Optionally, there may also be the spec.dependencies field filled with a list of npm packages that are used within this policy.

To apply such a policy in your cluster, simply create the JsPolicy object in your cluster:

kubectl apply -f policy.yaml

Under the hood, jsPolicy takes the spec.javascript code and creates a JsPolicyBundle object for you:

kubectl get jspolicybundle

The JsPolicyBundle will have the same name as the JsPolicy and the spec.bundle field will contain an optimized, base64 encoded and compressed version of the JavaScript code including all required dependencies. This bundle code is used by jsPolicy to actually execute this policy. If you update the spec.javascript in a JsPolicy object, jsPolicy will detect this change and re-generate the matching JsPolicyBundle.

JsPolicy + JsPolicyBundle Combo#

You may also find a combination of a JsPolicy object with a matching JsPolicyBundle object that both have the same name. In this case, the author of the policy already provides a pre-compiled JsPolicyBundle and the JsPolicy object will not contain the field spec.javascript.

To use such a combination, it is recommended (but not required) to apply the bundle first:

# Combo as separate files:
kubectl apply -f policy.bundle.yaml # apply JsPolicyBundle
kubectl apply -f policy.yaml # apply JsPolicy
# Combo as single file:
kubectl apply -f policy-and-bundle.yaml # should contain JsPolicyBundle + "---" + JsPolicy
Apply Bundle First

It is recommended to apply the JsPolicyBundle first because as soon as the JsPolicy exists in the cluster, it will be active immediately and if the corresponding JsPolicyBundle is not existing yet, all requests for this policy will fail until the JsPolicyBundle will be created. In the worst case, jsPolicy even denies the creation of the JsPolicyBundle because the JsPolicy you just created is matching the kubectl apply -f policy.bundle.yaml request and jsPolicy is unable to load the code for this policy.

npm Packages#

Someone may publish policy logic in the form of an npm package on, via GitHub's npm registry or in your own company-wide or private npm registry.

While you can use any npm package containing policy-related functions while writing your own policies, the easiest way to use policy code from npm packages, is to define a JsPolicy with an entry in spec.dependencies as shown in this example:

kind: JsPolicy
name: ""
operations: ["CREATE"]
resources: ["*"]
scope: Namespaced
"@jspolicy/policies": "^0.0.1"
javascript: |
import { disallowNamespaces } from "@jspolicy/policies";
disallowNamespaces(["default", "kube-system", /^prod-.*/])

This example policy.yaml file loads the npm package @jspolicy/policies as a dependency and could specify other dependencies similar to the dependencies statement in a regular package.json of a JavaScript project. Then, inside the spec.javascript field, this dependency is imported and a function of this package is called in our policy code.

To instantiate this policy, just apply it to your cluster:

kubectl apply -f policy.yaml

As with any JsPolicy object that provides the spec.javascript field, jsPolicy will generate a corresponding JsPolicyBundle. This bundle will also contain the code for the disallowNamespaces function since this function is imported in our policy code and will be directly embedded so that jsPolicy does not need to download any packages later on when executing this policy. This makes the execution of policies extremly fast even if they are using external packages.