Kosko 3.0 has been released a few weeks ago. There are many improvements and some breaking changes in this version.

Refined Error Report​

In the previous version, when you run kosko generate or kosko validate command, only the first error is reported. Error messages are cramped and there is a lot of useless information.

error - data/spec/replicas must be integer, data/spec must be null, data/spec must match exactly one schema in oneOf (path: "/home/tommy/Projects/kosko-old/examples/getting-started/components/nginx.js", index: [0], kind: "apps/v1/Deployment", name: "nginx")
ValidationError: data/spec/replicas must be integer, data/spec must be null, data/spec must match exactly one schema in oneOf
- path: "/home/tommy/Projects/kosko-old/examples/getting-started/components/nginx.js"
- index: [0]
- kind: "apps/v1/Deployment"
- name: "nginx"
    at Object.validate (.../node_modules/.pnpm/@kubernetes-models+validate@2.0.1/node_modules/@kubernetes-models/validate/dist/validate.js:9:21)
    at IoK8sApiAppsV1Deployment.validate (.../node_modules/.pnpm/@kubernetes-models+base@2.0.1/node_modules/@kubernetes-models/base/dist/model.js:44:20)
    at resolve (.../packages/generate/dist/resolve.js:63:29)
    at resolve (.../packages/generate/dist/resolve.js:50:34)
    at generate (.../packages/generate/dist/generate.js:39:56)
    at async generateHandler (.../packages/cli/dist/commands/generate/index.js:69:20)
    at async Object.handler (.../packages/cli/dist/commands/generate/index.js:108:24)

In Kosko 3.0 and kubernetes-models 4.0, you can get all errors in a single run. This means you don't need to modify your code and rerun kosko generate command anymore.

Furthermore, error messages become cleaner and more human-readable now. They are grouped by component paths, and error stacks are only displayed for non-validation errors.

components/mysql.js - 1 error

  ✖ ResolveError: Validation error
    Index: [0]
    Kind: apps/v1/Deployment
    Name: mysql

      /spec/template/spec/containers/0/env/0/value must be string

components/nginx.js - 1 error

  ✖ ResolveError: Validation error
    Index: [0]
    Kind: apps/v1/Deployment
    Name: nginx

      /spec/replicas must be integer
      /spec/template/spec/containers/0/ports/0/containerPort must be integer

error - Generate failed (Total 2 errors)

If you want to stop immediately whenever an error occurred, run kosko generate with --bail option.

kosko generate --bail

Or enable bail option in kosko.toml.

bail: true

Improved Nullable Type Error​

Besides Kosko, kubernetes-models was also updated to provide better error information for nullable types.

Let's say we have a nullable type as below.

interface IPod {
  spec?: IPodSpec;
}

When a value in spec is invalid, it throws a validation error like this.

data/spec must have required property 'containers',
data/spec must be null,
data/spec must match exactly one schema in oneOf

Only the first line in this error message is helpful. Other lines are very confusing and might make developers think they should set spec as null. Such error messages are removed in this version.

data/spec must have required property 'containers'

ESM Loader Support​

ESM loaders are finally supported in Kosko 3.0. You can use ESM loaders by adding loaders option to kosko.toml.

loaders = ["ts-node/esm"]

Or running kosko generate with --loader option.

kosko generate --loader ts-node/esm

See ECMAScript modules for more information about how to use TypeScript ESM loader.

Faster Kustomize Build​

In @kosko/kustomize 0.2, when you call loadKustomize function without kustomize CLI installed on your computer. loadKustomize will always try to call kustomize first then kubectl kustomize, which is slow if your components contain a lot of loadKustomize calls.

In @kosko/kustomize 1.0, successful kustomize CLI invocations are cached, so loadKustomize doesn't have to retry kustomize CLI every time.

Iterable Support​

Kosko 3.0 supports the iterable protocol. You can use Set, Map, or generator functions in components now.

// Set
export default new Set([new Deployment(), new Service()]);

// Generator function
function* gen() {
  yield new Deployment();
  yield new Service();
}

See Iterable and Async Iterable for more info.

Breaking Changes​

• Drop support for Node.js 12. The minimum supported Node.js version is 14.18.0 now.

• @kosko/generate - All errors thrown in generate and resolve functions are wrapped in GenerateError or ResolveError for better access to context.

• @kosko/generate - ValidationError is renamed as ResolveError.

• @kosko/generate - Multiple errors are wrapped in AggregateError.

• @kosko/generate - ResolveError.message no longer contains context information. You can access context from stack or direct access properties in the error value.

• @kosko/generate - fast-glob is replaced with a homemade glob function based on micromatch. The behavior will be slightly different. Please submit an issue if you encounter any unexpected problems.

• @kosko/yaml - Value type in Manifest has been changed from any to unknown. You might need to modify transform function to fix type errors. For example:

  // Before
  manifest.metadata.namespace = "foo";
  
  // After (Preferred)
  import { Pod } from "kubernetes-models/v1/Pod";
  
  if (Pod.is(manifest)) {
    manifest.metadata.namespace = "foo";
  }
  
  // After (Another way)
  import { IObjectMeta } from "@kubernetes-models/apimachinery/apis/meta/v1/ObjectMeta";
  (manifest.metadata as IObjectMeta).namespace = "foo";
  

• readonly attribute is removed from the return types of many packages.

Changelog​

• @kosko/aggregate-error@0.1.0
• @kosko/cli@3.0.0
• @kosko/common-utils@0.1.0
• @kosko/config@3.0.0
• @kosko/env@4.0.0
• @kosko/exec-utils@1.0.0
• @kosko/generate@3.0.0
• @kosko/helm@3.0.0
• @kosko/kustomize@1.0.0
• @kosko/log@1.0.0
• @kosko/migrate@4.0.0
• @kosko/require@4.0.0
• @kosko/template-deployed-service@3.0.0
• @kosko/template-environment@3.0.0
• @kosko/template@3.0.0
• @kosko/yaml@3.0.0

kubernetes-models 3.0 has been released last month. To upgrade to the latest kubernetes-models, run:

npm install kubernetes-models@latest

If you have installed any CRD packages, don't forget to upgrade them as well.

Smaller Package Size​

The package size of kubernetes-models 3.0 is reduced by 34% compressed, or 20% unpacked (compared to 2.0.2).

Several changes made the package size smaller in 3.0.

First, the following alias files are removed in 3.0. These alias files were introduced a few years ago. Removing these files can reduce the number of files and the size of the export map.

Next, type definition files are used to be stored in _definitions/<id>.js. In 3.0, they are moved to <apiVersion>/<kind>.js. This can also reduce the number of alias files, and import paths can be shorter, too.

Last, a new type TypeMeta has been added to @kubernetes-models/base package. Interfaces with apiVersion and kind will extend TypeMeta type now. This can remove doc comments in each type.

// Before
export interface IIoK8sApiCoreV1Pod {
  /**
   * APIVersion defines the versioned schema of this representation of an object. Servers should convert recognized schemas to the latest internal value, and may reject unrecognized values. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources
   */
  apiVersion: "v1";
  /**
   * Kind is a string value representing the REST resource this object represents. Servers may infer this from the endpoint the client submits requests to. Cannot be updated. In CamelCase. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
   */
  kind: "Pod";
}

// After
export interface IPod extends TypeMeta {
  apiVersion: "v1";
  kind: "Pod";
}

Better Import Suggestions​

Type definition files are used to be stored in _definitions/<id>.js, which are supposed to be hidden files. But sometimes IDEs get confused and show them in import suggestions. In 3.0, they are moved to more proper locations, which should provide a better IDE experience.

Before:

After:

API Machinery Package​

A new package @kubernetes-models/apimachinery has been released with kubernetes-models 3.0. This package includes types defined in kubernetes/apimachinery only. All CRD packages have been migrated to import this package instead of the whole kubernetes-models. This can reduce the size of dependencies of CRD packages.

// Before
import { IObjectMeta } from "kubernetes-models/apimachinery/pkg/apis/meta/v1/ObjectMeta";

// After
import { IObjectMeta } from "@kubernetes-models/apimachinery/pkg/apis/meta/v1/ObjectMeta";

Type Guard​

All classes with apiVersion and kind now come with a new static method is, which can be used to narrow down object types. Please note that this function does NOT validate the object itself. It just checks whether apiVersion and kind match or not.

import { Pod } from "kubernetes-models/v1/Pod";

const thing = { apiVersion: "v1", kind: "Pod" };

if (Pod.is(thing)) {
  // thing is an `IPod`.
} else {
  // thing is something else
}

Type guards can also be used in the transform function of @kosko/yaml.

import { loadFile } from "@kosko/yaml";
import { Service } from "kubernetes-models/v1/Service";

loadFile("manifest.yaml", {
  transform(manifest) {
    // Set all service type as "ClusterIP"
    if (Service.is(manifest)) {
      manifest.spec.type = "ClusterIP";
    }

    return manifest;
  }
});

You can see TypeScript documentation for more information about narrowing and type predicates.

Kosko now supports Kustomize files. With the new @kosko/kustomize package, you can load your existing Kustomize files into Kosko, and it also supports Kubernetes OpenAPI schema validation.

@kosko/kustomize uses the kustomize build or kubectl kustomize command to generate Kubernetes manifests and the @kosko/yaml package to load Kubernetes YAML.

First, you have to install either kustomize or kubectl CLI, then install the @kosko/kustomize package.

npm install @kosko/kustomize

Next, use the loadKustomize function to load Kustomize files.

const { loadKustomize } = require("@kosko/kustomize");

loadKustomize({
  path: "./dir"
});

See loading Kustomize for more details.

Last month, ECMAScript modules (ESM) support was shipped in Kosko 1.1. Today, you can use ESM not only in Node.js, but also in browsers. Currently only the following packages are browser-ready. Please make sure to update these packages before using Kosko in a browser.

• @kosko/env - 2.0.0
• @kosko/generate - 1.2.0

Programmatic API​

Kosko can be used in browsers via the programmatic API. In the following example, first we use dynamic import to load environment variables. Then, use the resolve function to resolve and validate components. And finally, print the resolved manifests with the print function.

import env, { createAsyncLoaderReducers } from "@kosko/env";
import { resolve, print, PrintFormat } from "@kosko/generate";

// Load environment variables with dynamic import
env.setReducers((reducers) => [
  ...reducers,
  ...createAsyncLoaderReducers({
    global: () =>
      import("./environments/dev/index.js").then((mod) => mod.default),
    component: (name) =>
      import(`./environments/dev/${name}.js`).then((mod) => mod.default)
  })
]);

(async () => {
  // Resolve and validate components
  const manifests = await resolve(
    import("./components/nginx.js").then((mod) => mod.default)
  );

  // Print resolved manifests
  print(
    { manifests },
    {
      format: PrintFormat.YAML,
      writer: { write: (data) => console.log(data) }
    }
  );
})();

See using in browser for more details.

More Examples​

You can try Kosko in the playground, or check the following examples.

• Webpack 5 - GitHub / CodeSandbox
• Static - GitHub / CodeSandbox
• Sync Environment - GitHub / CodeSandbox

Breaking Changes​

@kosko/env​

The following APIs were changed in this release.

• Environment class → Environment interface
• SyncEnvironment class → createNodeCJSEnvironment function
• AsyncEnvironment class → createNodeESMEnvironment function

You don't have to change anything, unless you initialize these classes manually.

// Before
const { Environment } = require("@kosko/env");
const env = new Environment(process.cwd());

// After
const { createNodeCJSEnvironment } = require("@kosko/env");
const env = createNodeCJSEnvironment({ cwd: process.cwd() });

Most popular apps are available as Helm charts. It was not easy to use them in Kosko directly. The all new @kosko/helm package can help you load Helm charts, and of course, it also supports Kubernetes OpenAPI schema validation.

@kosko/helm uses the helm template command to render chart templates and the @kosko/yaml package to load Kubernetes YAML.

First, you have to install the Helm CLI, then install the @kosko/helm package.

npm install @kosko/helm

Next, use the loadChart function to load Helm charts.

const { loadChart } = require("@kosko/helm");

loadChart({
  name: "prom",
  chart: "prometheus",
  repo: "https://prometheus-community.github.io/helm-charts",
  version: "13.6.0",
  values: {
    server: {
      persistentVolume: {
        enabled: true
      }
    }
  }
});

See loading Helm chart for more details.

Kosko comes with ECMAScript modules (ESM) support since v1.1. You can write components and environments in native ESM files. The following packages are updated for ESM support. Please make sure to update these packages before using ESM.

• @kosko/cli - 1.2.0
• @kosko/env - 1.1.0
• @kosko/generate - 1.1.0
• kosko - 1.1.0
• @kosko/migrate - 2.0.0
• @kosko/require - 2.0.0
• @kosko/yaml - 1.0.0

The biggest difference between CommonJS and ESM is that @kosko/env is asynchronous in ESM. This is because import() is asynchronous. But don't freak out, it won't break your current code at all. @kosko/env is still synchronous in CommonJS.

When retrieving environments in ESM, you MUST add await as the example below.

import env from "@kosko/env";

const globalParams = await env.global();
const componentParams = await env.component("demo");

Instead of module.exports, export components or environments with export default.

import { Deployment } from "kubernetes-models/apps/v1/Deployment";
import { Service } from "kubernetes-models/v1/Service";

export default [new Deployment({}), new Service({})];

For more details about how to enable ESM or programmatical usage, please check here.

Breaking Changes​

@kosko/yaml​

loadString and getResourceModule functions become asynchronous because of ESM support.

@kosko/migrate​

migrate and migrateString functions become asynchronous because of the breaking changes of @kosko/yaml package.

@kosko/require​

resolve function no longer allows resolve.AsyncOpts as options, please use ResolveOptions instead.

kubernetes-models​

kubernetes-models is also updated for ESM support.

• @kubernetes-models/base - 1.2.0
• @kubernetes-models/cert-manager - 1.1.0
• @kubernetes-models/contour - 1.1.0
• @kubernetes-models/crd-generate - 1.2.0
• @kubernetes-models/gke - 1.1.0
• kubernetes-models - 1.1.0
• @kubernetes-models/openapi-generate - 1.2.0
• @kubernetes-models/prometheus-operator - 1.1.0
• @kubernetes-models/read-input - 1.1.0
• @kubernetes-models/sealed-secrets - 1.1.0
• @kubernetes-models/string-util - 1.1.0
• @kubernetes-models/validate - 1.1.0

It has been a long time since the last stable release v0.9. Recently, I decide to implement some features that I always want to have at work. Hope these new features can also help you.

Nested Manifests​

In v1.0, arrays and functions in components are flattened. This is useful for sharing manifests across components.

For instance, a database in Kubernetes is typically composed by a Deployment and a Service. To include a database in a component, before v1.0, you have to flatten these two manifests in the component by yourself. After v1.0, they are flattened automatically.

In this way, a database can be used as a single resource, which can be used everywhere in your components.

function createDatabase() {
  return [new Deployment(), new Service()];
}

// Before v1.0
module.exports = [new Deployment(), ...createDatabase()];

// After v1.0
module.exports = [new Deployment(), createDatabase()];

More Information in ValidationError​

There was only path and index in ValidationError before v1.0. Sometimes it might be difficult to find where the error is. In v1.0, apiVersion, kind, namespace and name are added to ValidationError. The following is an example of the new error message.

ValidationError: data.metadata.annotations['dependencies'] should be string
- path: ".../components/config-api"
- index: [0]
- kind: "apps/v1/Deployment"
- name: "config-api"
    at resolveComponent (.../node_modules/@kosko/generate/src/generate.ts:81:15)
    at resolveComponent (.../node_modules/@kosko/generate/src/generate.ts:59:28)
    at Object.generate (.../node_modules/@kosko/generate/src/generate.ts:134:30)
    at generateHandler (.../node_modules/@kosko/cli/src/commands/generate/index.ts:156:18)
    at handler (.../node_modules/@kosko/cli/src/commands/generate/index.ts:200:20)
    at Object.run (.../node_modules/@kosko/cli/src/index.ts:12:3)

Loading Kubernetes YAML​

If you have been using Kubernetes for a while, you may have a lot of existing Kubernetes YAML files just like me. Instead of migrating YAML into JavaScript, try use the new package @kosko/yaml.

@kosko/yaml reads YAML files and transforms data into kubernetes-models classes, so your manifests are validated against Kubernetes OpenAPI schema.

const { loadFile } = require("@kosko/yaml");

module.exports = loadFile("manifest.yaml");

This package works better with "nested manifests", so please don't forget to upgrade to Kosko v1.0 first.

For more details, please check here.

Breaking Changes​

• Drop support for Node.js 8.
• @kosko/generate
  • The type of Manifest.index and ValidationError.index is changed from number to number[].
  • The type of Manifest.data is changed from any to unknown.