wpjunior / lasso

Low level generic controller framework

Lasso

Core controller framework used by Wrangler.

This framework is a bit raw, but can be used directly. The intention is try to standardize some boilerplate of building controllers.

Basic components

Package cache

This is a generic form of the generated SharedIndexFactory.

Package client

Generic form of the generated clientsets.

Package controller

The Controller is a simple approach that wraps the standard pattern of worker goroutines and workqueue. The package depends on the cache and client removing the need for generated clientsets, informers, and listers.

The SharedController type is an extension of Controller that adds the ability to register multiple handlers on a shared controller instance.

Simple Example

import (
	"context"

	"github.com/rancher/lasso/pkg/controller"
	appsv1 "k8s.io/api/apps/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/client-go/rest"
)

func MyController(ctx context.Context, config *rest.Config) error {

	// Setup types you want to work with
	scheme := runtime.NewScheme()
	appsv1.AddToScheme(scheme)

	controllerFactory, err := controller.NewSharedControllerFactoryFromConfig(config, scheme)
	if err != nil {
		return err
	}

	sharedController, err := controllerFactory.ForObject(&appsv1.Deployment{})
	if err != nil {
		return err
	}

	// Register a handler on a shared controller. If you a dedicated queue then use controller.New()
	sharedController.RegisterHandler(ctx, "my-handler", controller.SharedControllerHandlerFunc(func(key string, obj runtime.Object) (runtime.Object, error) {
		// obj is the latest version of this obj in the cache and MAY BE NIL when an object is finally deleted
		dep, ok := obj.(*appsv1.Deployment)
		if !ok {
			return obj, nil
		}

		// Don't some stuff ...

		// Get stuff from the cache
		sharedController.Informer().GetStore().Get(key)

		result := &appsv1.Deployment{}
		err := sharedController.Client().Update(ctx, dep.Namespace, dep, result, metav1.UpdateOptions{})

		// return the latest version of the object
		return result, err
	}))

	return controllerFactory.Start(ctx, 5)
}