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jsPolicy is a policy engine for Kubernetes that allows you to write policies in JavaScript or TypeScript.

jsPolicy Architecture
jsPolicy - Architecture


Although jsPolicy runs all of its components in a single container (not considering replicas when you scale up the replica number for high-availability), jsPolicy logically consists of three main components:

Webhook Manager#

The webhook manager is responsible for registering and managing admission webhooks with the Kubernetes API server, so that API server requests will apply the mutating and validating webhooks that are defined as JsPolicy objects.

V8 JavaScript Sandbox Pool#

For faster execution of policy code, jsPolicy maintains a pool of pre-heated V8 JavaScript sandboxes that can be used to run JavaScript code containing policy logic.

Policy Compiler#

The policy compiler is a controller that monitors JsPolicy resources and that creates and updates JsPolicyBundle objects for all JsPolicy objects that define the spec.javascript field. The compilation process looks about like this:

  1. Retrieve all required npm packages specified in spec.dependencies (similar to npm install downloading the dependencies specified in a package.json file of a regular JavaScript project)
  2. Run webpack to create a highly optimized bundle of JavaScript code that contains the code from spec.javascript and all dependencies while only bundling the functions that are actually needed for the execution of the code.
  3. Compress the bundle using gzip.
  4. Encode the bundle using base64.
  5. Store the bundle in spec.bundle within the respective JsPolicyBundle object.